BAHLA FORT AND OASIS RESTORATION AND REHABILITATION PROJECT

Follow-up report to the World Heritage Committee

on a mission to the Sultanate of O m a n

- 28 May-11 June 1995-

by

Jean-Louis Michon & Hubert Guillaud

World Heritage Centre, Unesco 1995

C O N T E N T S

1. Circumstances of the mission p. 3

2 . Ackowledgements p. 4

3 . T h e building and restoration methodology p. 5 3.1 Scope of the mission 3.2 Nature and composition of earth materials 3 3 Building procedures

4. The restoration strategy and schedule p. 6 4.1 Continuation of restoration work 4.2 The Qasabah problem 4.3 Constitution of a documentary basis

4.3.1 Architectural photogrammetry 4.3.2 Architectural surveys on work site 4.3.3 Archaeological research 4.3.4 Written and iconographie documentation 4.3.5 Aerial photographs and maps 4.3.6 Oral sources

5. The Master Plan for the restoration and rehabilitation of Bahla Fort and Oasis p. 8 5.1 Justification 5.2 The actions and actors S3 The intersectoral Commission for Bahla 5.4 Preparation and drafting of the Master Plan 5.5 Publication of the Master Plan

6. Recommendations ( summary) p. 9 6.1 Building materials and methods 6.2 Structural damage 63 Surveys and documentation 6.4 Establishment of a Master Plan for the rehabilitation of Bahla Fort and Oasis

7. International cooperation p. 10 7.1 Cooperation between the Omani and Moroccan Governments 7.2 Cooperation with Unesco

ANNEXES

Annex I.- Stereophotography of Bahla Fort p. 11 Annex 2.- Master Plan for Bahla - List of potential actors and activities p. 12

TECHNICAL APPENDICES

Appendix 1. - The traditional building materials and systems in O m a n and Bahla p. 13 Appendix 2. - M u d blocks and mortar p. 14 Appendix 3. - Renderings on adobe blocks walls p. 18 Appendix 4. - Building techniques p. 20 Appendix 5. - Suggestions for the treatment of gross structural decays p. 22

BAHLA FORT AND OASIS RESTORATION AND REHABILITATION PROJECT

Report on a mission to the Sultanate of O m a n

(May-June 1995)

by Jean-Louis Michon * & Hubert Guillaud **

1. Circumstances of the mission

1.1 The present mission and report are a direct follow-up of the visit which consultant J.-L. M i c h o n paid to Bahla site in December 1994 and on which a "Condensed Report" was prepared for the Wor ld Heritage Committee and sent to the World Heritage Centre of Unesco and to the Ministry of National Heritage and Culture ( M N H C ) of the Sultanate of O m a n in January 1995.

1.2 This Condensed Report, which is to be read in conjunction with the present one, contains an evaluation of the situation at Bahla Fort as in December 1994, compared to the one which the consultant had observed eight years previously, in October 1988, w h e n he had visited Bahla for the first time and recommended that the Fort and Oasis be included on the List of World Heritage in Danger (see : I C O M O S , J L M , "Rapport sur une mission au Sultanat d ' O m a n , Fort de Bahla, 5-14 oct. 1988").

1.3 It assesses the work that had been done during the years 1993 and 1994 by the Moroccan team in charge of the restoration and draws attention to the serious threats created by the accentuation of the decaying process and by some basic misconceptions in the restoration methods which were being applied to Bahla Fort (see "Condensed Report", section 2).

1.4 It contains two sets of recommendations which concern, respectively, the measures to be taken to insure a sound and authentic restoration of the historic Fort, and the elaboration of an integrated project aiming at rehabilitating the entire Bahla Oasis and making of it a protected area where the quality of life in an oasis would be preserved and demonstrated.

1.5 T h e first group of recommended steps ("Condensed Report", section 3.4) raised several questions concerning building materials and techniques which needed urgent clarification and specialized advice. This is w h y the World Heritage Centre of Unesco and the O m a n i Ministry of Culture ( M N H C ) agreed to call for the expertise of C R A T e r r e - E A G , a group of research scientists and field specialists of international repute based in France. M r . Hubert Guillaud, Secretary general of this Group, w a s designated as consultant and, jointly with Dr . J.-L. Michon, conducted the investigations and consultations which led to the practical solutions and conclusions hereafter exposed.

1.6 The mission started on M a y 29, 1995, w h e n a first meeting and working session w a s held at the M N H C under the chairmanship of H . E . Shaykh M o h a m m e d Bin A h m e d Al Harthy, Undersecretary for National Heritage Office. W e r e also present the following M N H C staff members : M M r s . Sâlim Ismail Bin Ali Souayd, Wakîl al-Wizârah, A n w a r Bin Abdallah A l Asfour, Engineer, Director of Projects, M a h m o u d Bin Sâlih Bin A h m a d , Director, General Relations and Services, A h m a d Bin Saqar Al-Naïmî , Director, Forts and Castles, M o h a m m e d Sa*îd A l Wahîbî, General Director of Heritage, Dr . Ali Shanfari, Director of Archaeology, Râbi M o h a m m e d D a h m a r , Architect M r . M o h a m m e d Alaoui, Chief Architect in charge of the Restoration works executed under the O m a n i -Moroccan Protocol, was also participating.

* Architect, Dr. in Islamic Studies, Member of I C O M O S Committee on Earth Architecture, Chambésy, Switzerland. ** Architect, Professor-Researcher, CRATerre / School of Architecture, Grenoble France.

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1.7 The discussion bore on questions which had been raised during the previous consultancy and which were on the agenda of the present mission, namely : . the measures to be taken to restore the mihrab of the small external mosque and the reception rooms ofBaytAl-Hadith; . the earth construction materials and techniques to be used in the whole restoration process; . the architectural, archaeological and other surveys and research to be undertaken prior to, or in conjunction with the restoration work; . the preparation of an integrated rehabilitation project for Bahla Fort and Oasis.

A schedule was established for the mission, including field work, consultations with operational staff and reporting to the Authorities of M N H C .

1.8 The consultants have examined the problems posed by the restoration and reconstruction of the Fort for several days in company of Chief-Architect M o h a m m e d Alaoui and of operational architect Tawfik Ouzgan, w h o is permanently affected to Bahla site. They also have had joint consultations on the site with H . E . Shaykh Al-Harthy and other representatives of the M N H C , and with two private civil engineers commissioned by M N H C to assist in the study and solution of the structural problems linked with the conservation of some dangerously ruined parts of the Fort (see infra, section.3.4).

1.9 At the final meeting which was held at the M N H C on June 10,1995 and which was attended, in addition to the participants present at the opening session, by H . E . Malallah Bin Ali Habib Allawati, Advisor to the Ministry, the consultants presented a summary of their conclusions and recommendations, stressing the need: - to apply carefully the building and restoration methodology developed and demonstrated during the field visits, - to undertake and complete as early as possible thorough surveys of the architectural and structural situation at Bahla Fort and Oasis, - to build up a solid documentation on Bahla history and past configuration, - and to start, as early as possible, the elaboration of a Master Plan for the rehabilitation of Bahla Fort and Oasis, enlisting the cooperation of a number of governmental departments.

There was a lively and constructive exchange of views on all these points, and the general feeling was that solid bases had n o w been laid for a successful continuation of the project (see infra, sections 6 and 7 ) .

2. A c k n o w l e d g e m e n t s

2.1 The consultants want to express their appreciation and gratitude to H . H . Sayyid Faisal Ibn Ali Al Said, Minister of National Heritage and Culture, for the kind welcome, generous hospitality and effective assistance offered by the Ministry.

2.2 Special acknowledgements are due to H . E . Malallah Bin Ali Habib Allawati and to H . E . Shaykh M o h a m m e d Al Harthy w h o have shown their keen interest for the project, giving m u c h of their time to organize and attend meetings and work sessions at the Ministry H Q and at Bahla site.

2.3 Thanks are also addressed to the architects in charge of the project, M M r s . M o h a m m e d Alaoui and Tawfik Ouzgan, with w h o m many hours have been spent on Bahla site to examine the delicate problems of restoration. They have to be commended for the care they have taken during the last months to depart from a "renovative" approach and pave the w a y toward a genuine conservative and restorative policy.

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3. T h e building and restoration methodology

3.1 Scope of the mission O n e specific objective of the mission was to study and determine building methods as close as

possible to the original ones, so as to warrant the preservation of the authenticity of Bahla Fort in the present and future restoration process. T o this end, a thorough observation was m a d e of the construction materials and techniques used in the past and, based on the results of this survey, advice was given on the choice of earth and other materials and on the most approriate building practices to be applied as from n o w on Bahla site. These two aspects of the mission are summarized in the following paragraphs, whereas detailed technical considerations are presented in Appendices 1 ,2 , 3 and 4 of the present Report.

3.2 Nature and composition of earth materials 3.2.1 The results of a chemical analysis which has been performed in March 1995 by the Laboratory of the Directorate General for Specifications and Measurements of the Ministry of C o m m e r c e and Industry on samples of the original building materials used at Bahla -earth blocks and renderings-have been confronted with the indications provided by a few simple tests performed on samples of earth extracted at a carreer distant circa 20 k m from Bahla and presently used to m a k e earth-bricks (adobes) at the Fort brickyard. The comparison has shown that the latter earth has a texture and characteristics very similar to the original one, which makes it a suitable material for the preparation of mud-bricks, mortar and renderings. Consequently, it has been decided to proceed with the restoration of walling at Bahla site privileging the use of mud-bricks, either rectangular or conical according to the nature of the original material.

3.2.2 The Fort brickyard, distant about 3 k m from the work-site, is well organized, presenting an orderly streamlining of the successive production steps, and it is run by an efficient team of 15 workers. Advice has been given there to arrive at a similar quality between the n e w and the old m u d -bricks. Practical demonstrations have been m a d e of ways to improve the shaping as well as the physical and mechanical properties of the mud-bricks, and to increase the daily productivity from the present output of around 500 units to 800-1*000 bricks per day.

3.3 Building procedures

3.3.1 The principle has been discussed and accepted to rebuild mud-blocks wallings already collapsed back to their original state and appearance -when properly documented-, referring as closely as possible to the Omani earth architecture tradition.

3.3.2 A particular care has to be given to the good bonding of the mud-blocks and to the regularity of the mud-mortar joints to warrant the cohesion and the mechanical stability of the restored walls.

3.3.3 N o particular reinforcing devices (such as concrete pillars) need be included in the width of the restored mud-block walls since they are respecting the safety limits of the bending stress (situated within the ratio of 1:10 between the width and the height of the traditional walls made of small masonry elements).

3.3.4 A series of samples of renderings which the operational staff had prepared on site with two types of sarooj -a traditional plastering mix of baked earth, palm-tree ashes and lime- have been examined for their adherence, texture and colour. Decisions have been agreed upon concerning the most suitable renderings to be applied on different supporting materials (stone, earth or sarooj) and on external or internal surfaces of the walls. Instructions have been given concerning the final treatment of the outward surfaces, which plays a most important part in the restoration process and must not contrast harshly with the ancient context.

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3.3.5 The reconstruction of collapsed terrace roofs has been discussed and solutions advocated to adapt the traditional system while avoiding the ruining attacks of termites. The beams made of palm-tree stems will be replaced partly by teck wood and partly, for reasons of economy, by local kendel wood. It has been suggested that contacts might be taken with specialized groups (like the Icomos International Committee on W o o d ) to find cheaper types of wooden material resisting the attack of termites. A s for the traditional ceiling system, it will be improved by the addition of a final layer of sarooj plaster for waterproofing.

3.4 Structural problems 3.4.1 O n the occasion of the two earlier consultant visits to Bahla, in 1988 and 1994, attention had been drawn to several parts of the Fort which needed urgent intervention. A m o n g them were the small extra- muros mosque with its multi-arched mihrab and the reception rooms of Bayt Al-Hadith with their threefold arcature, carved wooden doors and decorated ceüings. In both cases, the decaying process had reached a stage where no restoration work could be undertaken until a thorough architectural and structural survey had been completed and a remedial strategy had been determined in consultation with a qualified civil engineer.

3.4.2 Thanks to a prompt action by the M N H C , the cooperation of two civil engineering consultants, MMrs .Mahfodh Elyas Al-Balushi and M . M . Cheema -belonging to the counselling firm Al-Khutwah ("Pace")-, could be secured, and a joint consultation took place at Bahla site on June 6, 1995. The practical measures which were then discussed and commonly agreed upon to solve the two problems mentionned above are exposed in Appendix 5. Their implementation should be supervised by the Pace counsels and start as soon as possible after approval of a detailed planning by the MNHC.

4. T h e restoration strategy and schedule

4.1 Continuation of restoration w o r k U p to the present time, the repair and reconstruction works have been carried out on parts of

Bahla Fort which, although dilapidated, still presented relatively "readable" structures : the intra­muros mosque and Bayt AI-Jabal. W o r k will from n o w on be pursued, with an improved restoration methodology, on similarly readable buildings : the Western wall, Bayt Al-Hadith and the small external mosque. Restoration of the Great M o s q u e (Masjid Al-Jum'a) is planned for next year, when work should also start on the precinct wall of the oasis. Reconstruction of the sabla, the audience hall which had been inconsiderately destroyed some years ago, should also be envisaged in a nearby future, on the basis of a solid architectural and visual documentation.

For all the works, detailed plans should be prepared and submitted to the Consultative Group for Restoration, the creation of which has been advocated in the "Consolidated Report"of Jan. 1995 (parag. 3.4.g). This group, placed under the chairmanship of the Undersecretary for National Heritage Office, would comprise the operating architects, an archaeologist, an historian/documentalist, a civil engineer and, if possible, an international consultant or coordinator.

4.2 T h e Qasabah problem W h e n w e turn to the Old Citadel, the Qasabah, the situation appears to be particularly

complex, since this huge and impressive monument presents itself as an accumulation of crumbled walls, arches and towers the original configuration of which remains largely mysterious. Before any restoration and, possibly, reconstruction of this ensemble m a y be undertaken, one should possess a much better knowledge of the present and past state of the buildings as is n o w the case.

4.3 Constitution of a documentary basis It has therefore become imperative to constitute a documentary basis which, in addition to

being a working tool for the restoration and rehabilitation work, not only of the Qasabah but of the entire Fort and Oasis, will remain as an archive for historians, scientists, museographs and development staff. This documentation will include data obtained from the following sources :

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4.3.1 Architectural photogrammetry. A complete series of plans -ground, façades, cross sections- at the scale of at least 1/100th is a necessary preliminary instrument for conservation work. Realizing that the present operational staff is not equiped to effect a thorough survey of the entire Fort area and Qasaba, and knowing that a team of the German Mining M u s e u m of B o c h u m has taken stereophotographs of Bahla Fort some fifteen years ago (see A n n e x 1), every effort should be m a d e to obtain a photogrammetric restitution as complete as possible from these photographs. Not only one would get in that w a y the best possible survey of the Fort area, but comparison between the year when these photos were taken (around 1980) and the present time might give useful clues about missing parts of the walls and structures.

If not obtainable from the above-mentioned source, the general architectural and topographic survey of Bahla site should be ordered from some private company specialized in aerial and/or ground photogrammetry.

4.3.2 Architectural surveys on w o r k site A report (André Stevens, Unesco, N o v . 1986, p.6, parag.4) mentions the fact that "Bahla has

been the subject of a thorough architectural survey by the Department of Archaeology which prepared the plan of the town wall and a study of its most relevant features such as gates, towers, water channels, etc." A n investigation should be conducted to locate the relevant architectural file which, if found, would spare a good amount of time and effort to the present team.

In any case, the operational team should themselves make surveys of all the parts of the buildings where restoration work is to take place -and this prior to the beginning of the work-, using the scales 1/50,1/20,1/10 and even 1/1 for particular constructive or decorative details. For mat purpose, they should procure the necessary surveying and measuring instruments, including a theodolite and a telescopic graduated pole.

4.3.3 Archaeological research on Bahla site has up till n o w been very scanty. All the debris found during the cleaning operations and which m a y have some signification have been carefully kept aside and handled to the Director of Archaeology of the M N H C for further study. Excavations have been made in April 1993 by the French archaeological Mission in O m a n (Mr. Vincent Bernard) at one place in the Eastern part of the Fort to elucidate the occupation history of the site. S o m e layers have been identified and a few objects found : pottery sherds, coins, medallion, but no information concerning datation has been communicated to the M N H C up to n o w . Continuation and intensification of such research would be desirable and should start at an early date, so as not to interfere with the restoration work as it proceeds.

4.3.4 Search for written and iconographie documentation is very important. It should be conducted, firstly, with the architects w h o have been working with the M N H C on the restoration of forts and castles and m a y have taken photographs of Bahla site and castle m a n y years ago. Mention was made of M M r s . Enrico d'Errico, restorer of Jabrin Fort, and Paolo Costa, author, or potential author, of an article on "The Fortified Oasis of Bahla", the publication of which had been forecast in the Journal of Oman Studies, vol.9 (but which in fact does not seem to have appeared until to-day).

Systematic research should be conducted in the bibliography on O m a n : travel descriptions, geographic and historic handbooks and periodicals where the texts m a y be illustrated with photographs, sketches, drawings, engravings possibly evocative of a by-gone appearance of the Fort.

4.3.5 Aerial photographs and large-scale m a p s m a y exist in the archives of various government bodies and private firms concerned with land survey, agricultural development, water resources, defense, etc. and these sources should be tapped.

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4.3.6 Oral sources m a y also be quite informative, telling us, for example, what use was m a d e in the past of various sections of the monument . Conducting surveys and interviews with the local population, especially with the old m e n w h o are to be seen every morning and evening chatting amiably in the Old Souk of Bahla, could be, like the historical research, a task entrusted to social workers or to university students preparing a B . A . , M . A . or P h . D . in Arts.

4.3.7 Location of the documentary basis All the documentation so collected should be properly classified and put at the disposal of the

operating team and other collaborators of the project in a large room, adequately furnished with file cabinets and tables for easy consultation of the plans, maps and other documents. A n ideal arrangement would be to have the documentation room located in a building situated in Bahla area and specially affected to the Bahla project. This Bahla Project Office would also house the architectural unit with its drawing room (at present, no adequate space seems to exist for the architectural work), and it would serve as a central point where the various participants to the project could meet and coordinate meir roles within short distance from the site.

5. T h e Master Plan for the Rehabilitation of Bahla Fort and Oasis

5.1 Justification 5.1.1 It has been clearly stated, during die procedure of inscription on the World Heritage List, that Bahla Fort was not per se a monument of universal value, but mat it might constitute widi the surrounding oasis, properly protected and rehabilitated, a typical ensemble representative of oasis life and culture, thus deserving world interest and recognition.

5.1.2 It is also obvious that the rehabilitation of the ensemble Fort/Oasis is a task which cannot be carried out by the M N H C alone, but that it has to be a joint venture, necessitating intersectoral cooperation. This means that an integrated plan of action, i.e. a "Master Plan", has to be drawn out, defining the various tasks to be performed by each of the governmental and other entities associated with the project.

5.2 T h e actions and actors. 5.2.1 The general idea being to raise Bahla, fort and oasis alike, to the status of what one m a y call an "Oasis National Park", the actions taken will be of three kinds, as has already been exposed in the 1988 Consultant Report to the World Heritage Committee (JLM Oct.88, sections V E / A , B , C ) , creating adequate conditions for : - the reuse and, at the same time, continuous maintainance of the Fort; - the rehabilitation and development of the environment, not only in the immediate neighbourhood of the Fort, but within the small city of Bahla and in the whole oasis, including its twelve kilometers-long precinct wall; - the promotion of cultural tourism in Bahla and the surrounding region, special emphasis being laid on demonstrations of the beauty and harmony of folk arts and traditions.

5.2.2 In view of facilitating the preliminary contacts and consultations with the various partners involved in the project, a list of "Potential Contributors and Activities" has been established at the request of H . E . Shaykh Al Harthy (see A n n e x 2). Although by far not exhaustive, this list should be helpful, at the present juncture, to form an idea of the scope of the project, inform the potential partners of the objectives to be covered by the Bahla Rehabilitation and Development Project, and incite them to formulate ideas and proposals concerning their possible contributions to the advancement of this c o m m o n undertaking.

5.3 T h e intersectoral Commiss ion for Bahía The next step would consist in creating, under the sponsorship of the M N H C , a special

Commission for Bahla, with its o w n statutes, rules of procedure and financial resources. This Commission should include high-level (executive) representatives of the principal Ministries involved. It would be entitled to enroll the participation, on an ad hoc basis, of the necessary consultants and experts.

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5.4 Preparation and drafting of the Master Plan The main task of the Commission, in the first instance, would be to examine the data,

including cost estimates, provided by the different actors, to harmonize them so as to avoid any overlapping or redundance between the various sectors and, finally, to incorporate them into a Master Plan.

5.5 Publication of the Master Plan Once drafted and finally approved, the Master Plan should be published in the form of a clear

and attractive brochure, with a short historic introduction, architectural drawings and good pictures of the Fort and oasis life. It would thus not only provide a strategic guide for the conduct of the rehabilitation project but also serve as an information document and an aid for fund-raising activities.

6. Recommendat ions ( s u m m a r y )

Since most recommended measures of a methodological or strategical character have already been exposed in the previous sections of this report, and since all recommended measures of technical character are exposed in the following Appendices, only a brief review will be made hereunder of the subjects requiring attention.

6.1 Building materials and methods Counsels on the fabrication of adobe and mortar, on the choice of renderings and on the

building procedures to be applied on the work place are given in Appendices 2, 3 and 4 and should be strictly adhered to.

6.2 Structural d a m a g e Measures which have been devised to remedy the gross structural damage suffered by

valuable parts of Bahla site: the reception rooms of Bayt al-Hadith and the small external mosque are described in Appendix 5. Cooperation with the counselling firm Al-Khutwah ("Pace") which has proved quite useful for the solution of these problems {supra, section 3.4) should be continued and extended to the study of other structural damage, notably in the Great Mosque and in the Qasabah (for the surveillance and support of fragile structures). It should nevertheless be made clear that no restoration work (except urgent consolidation measures) m a y be started without previous consultation with and approval by the ad hoc consultative group mentioned above (see section 4.1).

6.3 Surveys and documentation 6.3.1 A complete set of plans and elevations showing the state of Bahla Fort prior to restoration must imperatively be obtained, preferably by photogrammetric restitution of the photographs taken by the Mining M u s e u m of Bochum {supra, section 4.3.IJ.

6.3.2 Architectural surveys should always be carried out by the operational team before starting restoration work on any part of the Fort and other buildings. Priority should be given to the architectural survey of the Great Mosque. Although a survey of the precinct wall of the Oasis seems to have been done in the past (see section 4.3.2), it should be repeated if the relevant plans cannot be retrieved.

6.3.3 Architectural surveying should also be extended to the little city of Bahla and to the oasis where traditional earth-buildings worthy of being preserved, like the old souk, large farm houses and family mosques are disappearing, often to be replaced by constructions which are in disharmony with the environment.

6.3.4 In addition to architecture, documentation to be collected includes archaeology, cartography, iconography (photographs, drawings, paintings...), bibliography and oral accounts on Bahla {supra, sections 4.3.1 to 4.3.6).

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6.3.5 All the documentation should be properly classified and kept at one central office where it could be consulted. The same office would house the architectural unit and serve as a meeting place for the participants to the project (section 4.3.7).

6.4 Establishment of a Master Plan for the rehabilitation of Bahla Fort and Oasis

6.4.1 A basic instrument for a joint cooperation between all departments concerned, the Master Plan should be prepared by a special Commission comprising high-level representatives of the main Ministries (see "Condensed Report", Jan. 1995, p.6,b and supra, sections 5.2, 5.3, 5.4).

6.4.2 W h e n finalized, the Master Plan would be published in the form of an attractive brochure to be used as a guide and public information instrument {supra, section 5.2.5).

7. International cooperation

7.1 T h e cooperation between the O m a n i and the M o r o c c a n Governments which has proved so useful for the conservation of the architectural heritage in the Sultanate should be pursued, so that a continuity be maintained in the work performed by the present team employed at Bahla. The methodology of restoration has n o w reached a satisfactory development and its efficiency would be seriously jeopardized in case deep changes occurred within the present operational staffing.

7.2 T h e cooperation with Unesco should continue so as to insure periodical review of the project by consultants, preferably at six months intervals. It might help incidentally to respond to special needs, like the organisation of training seminars on earth construction and maintainance of earth buildings, the fund-raising campaign (for which Unesco might act as liaison agent between O m a n and potential donors), the establishment of programmes of cultural tourism or the promotion of traditional handicrafts.

B y w a y of conclusion, the consultants wish to express their confidence in the fact that, thanks to the concerted efforts of the Omani Authorities and the international community, Bahla m a y become a prestigious Oasis Park which will attract the attention of the young Omani generations and of the foreign visitors on the quality of life in a place where the Bounty of the Creator and the intelligence and efforts of m e n have combined to shape a beautiful and harmonious environment.

Geneva ( C H ) and Grenoble (F)

June 1995

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A N N E X !

Bahla-fort (fig. 11 and 16) is an important centre of the Bani Nabhan tribe ¿/nasties

from the mid-13th century to the beginning of the 17th century), located 30 km to the west of

Nizwa. It has a mud brick town wall 12 km long, which bears witness to Bahla's former size.

Stereophotos were made of the fortress wall (fig. 12), many of the larger buildings

(fig. 13) and some of these buildings'interiors. In a later campaign the set of photos will be

completed (additional parts of the fort, photos from the balloon). Mention should also be made of

a stereopair of photos taken with a Wild RC.8 aerial camera. We intend to combine the terrestrial

and aerial photos in a bundle block adjustment.

The photos will be measured with a Zeiss Planicomp C.100. After space resection and de­

termination of initial values of the exterior orientation and object-points, the determination of

control-points for the photogramnetric plotting will be done by bundle ajustment, using a little

geodetic data, such/as ta chyme tri call y measured points and some measurements of length.

s y

/

Fig. 15 - Ground plan sketch of Bahla fort, O m a n , with Rolleiflex SLX Rëseau-Camera positions.

Extract from "Photogramaetric Surreys of Islamic Architecture", Publication prepared following the International Symposium, on Photogrammetry applied to Is lamic Architecture (Tunis, October 1984)

I C O M O S , 1986 , p . 19

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ANNEX 2

BAHLA FORT AND OASIS REHABILITATION PROJECT

- Establisment of a Master Plan -

Potential Contributors and Activities

Tasks / Equipments to be provided Responsible Entities

- Coordination & General Supervision of Project

• Inventory, survey and documentation of the World Heritage Site

• Restoration of the Fort, extra-muros mosques and oasis precinct wall

• Planning re-use and maintenance of Fort, jointly with interested partners

• Creation of a site m u s e u m and Cultural House within the Fort

• Advisory services and technical assistance for the rehabilitation of traditional

architecture within Bahla village (Old Souk) and oasis

- Participation of Local Authority in the implementation of the project and

application of the regulations concerning it

- Information

• of the population of Bahía concerning the project, in order to

enlist full cooperation of the inhabitants in the rehabilitation process

• of the general public, through the media, on the status of Bahla as

World Heritage Asset

- Rehabilitation of the traditional water system within and outside the Fort

(falàj, wells, cisterns,...)

- Electricity and water systems within the Fort and in the surrounding area

- General protection and valorization of the Bahla area ;

layout of n e w equipments and facilities (for tourism, handicrafts,

education)

- Site and services planning

• around the Fort : curbing and motor traffic, layout of access road

and parking area

• within the oasis : problems of environmental sanitation (waste and

sewage disposal), vector control, drinking water quality

- Construction of new houses according to specifications laid for the protected

Bahla area

• Census of land ownership for potential conservation and development projects

• Drafting of an Act establising Bahla as World Heritage Site and setting up

a Site Commission and rules for its funding andfunctionning

Ministry of National Heritage

and Culture

Office of the Wali of Bahla

Ministry of Information

Ministry of Water Resources

Ministry of Electricity & Water

Ministry of Regional

Municipalities & Environment

Directorate General of Tourism

Ministry of Social Affairs

& Labour

Ministry of Education

Ministry of Communications

Ministry of Health

Ministry of Housing

N . B . : Several Government Entities are not specifically mentioned in relation with one particular task because their cooperation and

assistance are automatically sought for any important national undertaking. They are, to our best knowledge the Diwan of Royal Court, the

Majlis Ash-Shura, the Ministry of Interior, the Ministry of Finance & Economy, the Development Council.

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TECHNICAL APPENDICES

Appendix 1. - The traditional building materials and systems in Oman and Bahla

T h e typical building materials, elements and systems which have been used for centuries in O m a n are basically the following :

For walling : • stones - for ramparts, basements and parts of walling - put up with m u d or "sarooj" A-1 mortar ; • m u d blocks, either rectangular or conical, mainly used for thick walls erected o n top of stone basements and also bonded with m u d mortar.

For roofing : • pa lm tree b e a m s , ceilings in pa lm tree leaves and w o v e n matting in pa lm tree fibers covered with tamped earth, protected or not with a waterproof "sarooj" rendering.

For plastering : • m u d and straw (first coat) covered with "sarooj" or "juss" A-2 (second coat), for internal renderings ; • "sarooj" for external renderings laid in one or two coats and m o s t of the time finished with a "sarooj" slurry (as a w a s h painting), applied equally o n stone and on m u d blocks.

All these building materials and systems have been used on Bahla site, i.e. :

• in the Fort, the two mosques extra-muros, the Old Souq of Bahla city and the great majority of people's dwellings and families' mosques in the oasis ; and • on die precinct fortified wall of the oasis, about twelve kilometers long.

A t Bahla citadel and Oasis site, a particular attention should be given to privilege the use of these traditional building materials and systems in the methodology and in the on going process of restoration.

A-1 • "Sarooj" : traditional preparation made of clayey soil added with limestone (or gypsum, see comments on chemical analysis in appendix 3, A.3.I., infra), laid on trunks of palm tree, slowly burnt together and then crushed before to be used by adding water to constitute a mortar for plastering. A- 2 "Juss" : traditional rendering made of gypsum, generally used as a slurry on top of a mud and straw first coating. The "juss" is also used for surface decoration, as well directly carved on the wall as moulded in small elements.

Appendices, p. 13

Appendix 2 . - M u d blocks and mortar

A . 2 . 1 . Traditional m u d blocks and mortar used at Bahla

A . 2 . 1 . 1 . M u d blocks

M u d blocks at Bahla are either rectangular or conical. T h e first type seems to have been used more for the construction of dwellings and the second for the Fort. Identified dimensions are 30 x 15 x 15 c m (L x w x h) for the rectangular type and 20/25 c m of diameter for the base of the conical with about 20 c m in height. But looking at the walling of the Fort, it seems that bigger conical blocks have been used. T h e raw material used to m a k e these m u d blocks is a clayey m u d mortar, probably taken from the banks of an "oued" located in the vicinity. This m u d mortar is added with small pebbles and also with s o m e barley straw chopped in small wisps. These added materials play an important part to reduce the shrinkage of" this plastic material.

T h e chemical analyses m a d e by the Laboratory of the Ministry of C o m m e r c e and Industry on samples of the two types of m u d blocks taken from the site confirm the presence of good clayey minerals with an important silica fraction (Si02). T h e typical ratio combining the Alumine sesquioxide (A1203) with the Iron sesquioxide (Fe203) on this Silica fraction, gives values situated between 0,30 to 0,40 which attest that w e are in presence of an Illite clayey mineral rather than of Kaolinite. This type of Clayey mineral can be considered as stable. T h e presence of Calcium Oxide (CaO) in a good average quantity cannot be interpreted because it is directly linked with the m o d e of analysis, unknown. T h e average value of Magnes ium oxide ( M g O ) is rather acceptable. The very low presence of sulphur (S03) is not alarming.

A . 2 . 1 . 2 . M u d mortar

M u d mortar used at various places to bond the m u d blocks seems to have the same origin and quality as the mortar used to mould the m u d blocks themselves. Nethertheless, its apparent matrix, with not m a n y pebbles and no straw, shows a good mechanical stability with no shrinkage or just some little micro cracks which indicate that w e are in presence of a more sandy soil.

A . 2 . 2 . N e w m u d blocks used for the restoration

A.2 .2 .1 . Dimensions and quality

N e w m u d blocks produced at the brickyard of the site are respecting the original shaping and dimensioning of old materials previously described, both for the rectangular and conical types. Nethertheless, the conical which w a s traditionally moulded by hand is n o w moulded with iron moulds, the traditional k n o w - h o w being actually lost. Another type of rectangular blocks, longer than the more current one (50 x 15 x 10/12 c m ) is produced to be used for strengthening angles of the walls, acting as a bonding chain in both directions. This building system, according the team of architects in charge of the restoration at Bahla, has been identified on parts of old constructions of the citadel.

S o m e comparisons have been m a d e by visual examination on old and n e w m u d blocks, particularly to precise their visible texture. It seems that n e w blocks are containing pebbles of a bigger size than those observed on old blocks. The straw itself seems to be chopped in longer wisps in n e w blocks than in old ones. T h e angles of the n e w blocks are a bit fragile and crumbly. Possible improvements have been discussed at the brickyard site. But, globally speaking, w e observe no important shrinkage on n e w blocks attesting a good practice in the moulding process as well as fairly good physical and mechanical properties.

Appendices, p. 14

A.2 .2 .2 . T h e brickyard : general organization

A visit at the m u d block production yard located circa 3 k m from the citadel of Bahla, in direction of Nizwa , has been m a d e to check the whole process and practices for the preparation of the m u d mortar and the moulding of bricks.

This brickyard is an exemplary specimen of a good , clear and clean organization. O n an approximative 60 m . x 80 m . rectangular site, fenced all around, the areas corresponding to the successive steps of the production are correctly positioned. T h e raw soil, the gravel and the barley straw to be added to the mortar are delivered from " O u e d W a d i Qariat" (southern direction to Ibri) and from Nizwa in necessary quantities according to the timing of production of m u d blocks. T h e dry materials being added (soil and gravel), are mixed with water and kneaded during 20 days, every day, before the moulding. This practice ensures a very good and homogeneous mixing of the mortar.

W e only observed that the straw w a s added too late, on the day w h e n the blocks are moulded. This practice would have to be changed by adding the straw earlier (6/7 days before moulding), to improve the stabilizing effect of the fibers (generation of lactic acid with the deterioration process) as well as for reducing the shrinkage of the material and to push up the tensile resistance of the blocks. This straw would have to be chopped in shorter wisps (7 to 10 c m ) to facilitate their better distribution in the mortar.

A .2 .2 .3 . The production of the m u d blocks

Rectangular m u d blocks are shaped in one unit w o o d e n moulds and conical blocks in one unit iron moulds. The design of the moulds is correct and warrants a good durability of these tools. Iron moulds for rectangular blocks were also seen on the site but not used during our visit.

While observing the moulding process, it has been noticed that the plasticity of the mortar (optimum moisture content) has to be different for the production of either rectangular or conical blocks. T h e same plasticity m a y be too high for conical shaping and leads to a sinking and deformation of the blocks. For rectangular blocks, the plasticity of the mortar can be just a bit higher and w a s observed as good.

T o improve the quality of the blocks in shaping as well as in resistance, it has been practically shown h o w to throw the mortar with strength into the mould and to compress it with the fingers in the four angles of the mould. This gives a more homogeneous block with regular edges, less crumbling at its corners.

T o facilitate the removal of the fresh m u d block out of the mould, it has been advised to plunge the mould entirely into a tank of water, every time before throwing the mortar in it, rather than to only clean it with some water as it has been observed. Under the very hot and dry local climate, the control of the humidity of the mould is a real problem.

The curing process of freshly moulded blocks has been found very correct, with a first 10 days curing phase on the moulding area, in horizontal and then in vertical position, before a second phase of final storage on an other area and under a plastic sheet which warrants a slow final drying process.

A .2 .2 .4 . Observations on raw materials used at the brickyard.

Simplified field tests have been carried out at the brickyard to characterize the raw soil. The essay of cohesion, called "cigar" test, shows a breaking of the m u d cigar into two pieces at about 11 to 12 c m . This confirms that w e are in presence of a clayey and silty soil lacking of

Appendices, p. 15

sand but not too plastic. The other simplified test of sedimentation with a bottle filled with 1/4 part of soil and water, mixed and then left for décantation, confirms a correct average of the clayey fraction and the presence of a fairly great amount of silt as well as not too m u c h sand above the thin fraction. The adding of pebbles improves the grain size distribution of this plastic soil but there is always a significant shortage of coarse sand which would give a more ideal texture to the soil.

It has been advised to use a more sandy and gravely soil with the same clayey and silty content and to sieve the gravel fraction at a m a x i m u m of 20 m m in diameter to improve the texture and the structure of the soil. This addition of chopped straw is always required to stabilize the clayey and silty fraction of this soil, the proportion added being kept at a m a x i m u m of 20 to 30 k g / m 3 (4 to 6% in volume).

A .2 .2 .5 . The productivity at the brickyard.

15 w o r k m e n , a m o n g them 4 brickmoulders, are working at the brickyard and are producing an average of 500 m u d blocks ("adobe"), each day. Referring to well-known figures, this productivity corresponds to the mobilization of 5 workers which means that w e are in a situation of low-productivity. Considering that a higher level of production would be desirable for a programme of restoration which will absorb more and more m u d blocks (for the rampart e.g.), the following advice has been given to improve productivity :

• add and mix the straw to the m u d mortar together with the water, 6/7 days before the moulding step, and knead it every day before moulding ; • use two units wooden moulds for the production of rectangular adobes ; • adapt the correct water moisture content (plasticity) for the moulding process ; this can be easily corrected with a fairly high level of water if the texture of the raw soil is more continuous in grain size distribution (more coarse sand) ; • plunge the mould into water entirely before moulding. Maintain the mould into water during the no moulding period because of the very hot and dry climate. • try to optimize the organization process between workers w h o are delivering the mortar to the brickmoulders ; • optimize the gesture of the brickmoulders by throwing with strength bigger quantities of mortar in one stroke into the mould (close to the m a x i m u m necessary amount to shape each m u d block).

It is believed that applying these pieces of advices will enhance the productivity of the brickyard up to 800 / 1 000 adobes per day.

A.2.2 .6 Improving the mechanical resistance of the adobes

Correction of the texture of the raw soil used at the Bahla site brickyard, to obtain a more continuous grain size distribution can be achieved by adding more coarse sand and pebbles (sieved at a m a x i m u m of 20 m m in diameter). Experiments to approach this improved texture would have to be done and checked with the simplified test of décantation performed at the brickyard and then confirmed with the standard sieving analysis in a road laboratory. This could also ensure an improvement in the mechanical resistance of the adobe blocks in dry compressive strength tested by crushing. O n the other hand, the presence of straw chopped in shorter wisps (7 to 10 c m ) would also improve the tensile resistance of the blocks. T o precise data on this mechanical resistance as well as for compressive and tensile strength, s o m e essays would have to be done with a small field press, the design of which has been exposed to the operating architects in its principle. T h e technical documentation contained in the "Earth construction guide" (CRATerre) which have been given to them and the plan of the field press reproduced in this technical appendix will be helpful to them.

Appendices, p. 16

FIELD PRESS TO TEST THE MECHANICAL RESISTANCE OF THE M U D BLOCKS

(source : C R A T e r r e - E A G )

A test block is placed (on one of its larger (aces) across two 25 mrt) diameter tubes laid 20 c m apart. In the upper axis of the block, parallel to its smaller face, a further identical tube is placed with a loading plate balanced on top of it. T h e plate is carefully loaded at a rate of 250 kg/minute with other blocks, until the test block fails. This gives a bending strength value. Multiplied by 5, this value indicates the minimal compressive strength.

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Appendices, p. 17

Appendix 3 . - Renderings on adobe blocks walls

A . 3 . 1 . Old types of renderings observed at Bahla

A typical range of renderings can be observed on old constructions at Bahla. External renderings are m a d e either of m u d and straw or of "sarooj". Internal renderings are m a d e of earth and straw covered with a final coating of "sarooj" or "juss" (gypsum coating or slurry).

The chemical analyses of these traditional renderings m a d e on samples taken from the site show the following results :

• For m u d plasters, the typical ratio between the amount of Alumine sesquioxide (A103) and Iron sesquioxide (Fe03) on the Silica fraction (Si02) results in a 0,25 value. W e are below the typical value of the illite (0,33) and so in presence of a fairly unstable clayey mineral. This explains w h y a great quantity of straw has been added in the typical m u d mortars observed at Bahla. O n the other hand, it could be interesting to k n o w more on the possible chemical reaction between the clayey fraction and the presence of Calcium Oxide (CaO) which could result in a kind of pozzolanic reaction ("natural" stabilization). But this depends a lot on the quality of the clayey mineral.

• For "sarooj" plasters, w e have a typically smaller importance of the silica fraction whereas the typical ratio between the amount of Alumine sesquioxide (A103) and Iron sesquioxide (Fe03) on the Silica fraction (SÎ02) results in a 0,85 to 0,87 value. W e are here in presence of very stable clayey minerals (maybe more kaolinitic) which could lead to a good physico-chemical reaction with the Calcium oxide (CaO) fraction, maybe releasing some "natural lime". But also, w e have indeed a great amount of Sulphur oxide (S03) that, when combined with the Calcium oxide fraction, could lead to the creation of gypsum (CaS04). O n e has then to be very cautious in the definition of what is exactly a "sarooj" which seems more to be a gypsum plastering than a lime plastering. This could be explained by the quality of the raw limestone added during the preparation of the "sarooj", which could be more a "gypsum" stone ; in which case the two traditional kinds of plasters respectively called "noura" (white colour) and "juss" (red and brown colour) could be more gypsum plasters. This could have to be checked by specific analyses made by competent laboratories in O m a n .

A .3 .2 . Essays m a d e at Bahla site to define renderings to be used on m u d and stone walls

A s was suggested during the last field mission in December 1994, various essays on renderings have been made under the control of the Moroccan architects at various periods during the last months, namely on : 19-21 December 1994, 17 January 1995, 29 April 1995 and 16 M a y 1995.

All the essays made with earth and straw as well as with "sarooj" mortars have been examined. All of them are globally looking satisfactory, attesting a good practice. These samples present the following properties :

• M u d and straw plasters present a good mechanical adherence on their support, i.e. the first coating mainly m a d e with a "sarooj" mortar ; no big cracks and just s o m e micro cracks for a little part of them. A top surface finishing with a slurry of "sarooj" or even of "juss" would easily fill these small micro cracks. A m o n g all essays experimented with m u d and straw plasters, the most satisfactory is by n o w being tested on parts of external walls located close to the South-West main entrance of the citadel. T h e practice which has been observed looks good but an evaluation will have to be m a d e after s o m e time of curing and exposure to meteorological agents (rain, wind and sun). It is important to note that, basically, this type of m u d and straw plaster would seem more

Appendices, p. 18

appropriate for internal renderings. However some parts of external renderings at Bahla are showing the use of this type of plaster. T h e present experiments are therefore very important, particularly at places where a continuity between old m u d and straw plasters and newly m a d e ones m a k e it possible to restore parts of walls close to their original state.

• "Sarooj" plasters used as first coat as well as finishing coat are m a d e with two types of "sarooj" mortar. O n e is coming from Nakhl where a production unit has been set up for all working sites actually managed by the Ministry of National Heritage and Culture, and an other type is coming from a small craft production unit located at Nizwa . T h e first one seems to have a better resulting quality in use, as well as in colour and in texture (more pink than the other which is more brown and even grey). The adherence of these finishing coats m a d e of "sarooj" on their walling support (also m a d e of "sarooj") seems very good after s o m e months. Essays have been m a d e with variations in the components of the mortar (either mixing the two types of "sarooj" or adding s o m e more sand). Finally, the most satisfactory results have been given by "sarooj" coming from Nakhl added with sand in 2 : 1 proportions. This plaster has been already tested on the restoration of the external mirhab of the M o s q u e intra-muros and gives a good aspect in colour, texture and adherence. It has thus been decided to use it for external renderings on repaired and reconstructed walls.

For internal renderings it has been also suggested to test other finishing solutions with earth and straw as first coating and a slurry of "juss" (gypsum) as finishing coat, a type of plastering which has been observed, e.g. in the reception rooms of the "Bayt al-Hadith".

• A particular attention will have to be given to the aesthetic finishing of the renderings -both external and internal - in order to obtain a smooth and rounded shaping, particularly at salient edges (outside angles and jambs of openings). T h e general surfacing aspect of the renderings shall not be too flat, regular and polished but will aim at approaching as closely as possible the character of traditional O m a n i renderings.

• The use of plasters on outside façades, particularly for the rampart of the citadel, shall not be systematic or uniform and will have to be adapted to the past and available photographic documentation. This is particularly important w h e n stone and m u d blocks are in close continuity showing a kind of "stair" design where stone parts are not or only partially plastered. G o o d examples of this aesthetic treatment can be observed on the restored fort of Mutrah.

• Old parts of plasters which are in a good state of conservation with a good adherence have to be safeguarded. Only a cleaning (light surface brushing) needs to be done. W h e n s o m e parts of them have to be removed, it is only to warrant a good continuity (mechanical as well as aesthetical) with restored surfaces. In such situations, essays have to be done to find a similar quality and aspect between the old and the n e w plaster.

A . 3 . 3 . Implementing renderings on m u d blocks walls

Renderings which have been executed at Bahla since the conservation work has started can be observed on the "renovated" part of the Fort, i.e. "Bayt al-Jabal" and the M o s q u e intra-muros. Only the first coat of these renderings has been m a d e s o m e months ago and the composition presented as pure "sarooj" would have to be checked. T h e colouration looks fairly pink with white traces ; the surfacing looks very flat, with sharp salient edges at the external angles of the constructions and at the jambs of openings. This "renovated" aspect cannot be accepted for the subsequent practice of renderings which has to be compatible with a "restoration" process aiming at a more genuine aspect, smoother and rounded.

Appendices, p. 19

Referring to the very dry and hot climatic conditions, the rules of the art for plastering on m u d blocks or on stone walls have to be particularly respected. It is worth reminding here these rules which should be followed with great attention and care :

/ - General conditions :

• Wait for the complete settlement of the masonry before starting the plastering process. This could take a m i n i m u m of five to six months, according to the thickness of the walls. • D o not execute plastering during the very hot season or under rainy or windy conditions (here in O m a n during November/December) . Prefer the "colder" (if any) season (here in O m a n from January to the beginning of M a y ) • D o not execute plastering under direct sun on the walls but rather under shadow (either projected or cast) and preferably during early or late day time (this could require a specific work schedule for the plastering work).

ii - Making the plasters :

• Prepare the support (the wall) : brush it and m o v e d o w n all dusty and crumbly parts. • Moistening the wall : spray water in sufficient quantity (but not too m u c h ) and control the rapid process of evaporation. A dry support would considerably reduce the adherence of the first coating. • Executing the first coating : using a trowel, throw on the mortar plaster with strength, taking care not to m a k e a too thick coat (max imum of 5/8 m m ) . D o not plaster d o w n to the ground level to avoid the capillary suction from the bottom of the wall. Adapt the thickness of the plaster to the natural shaping of the wall to obtain an attractive aspect. Prepare the adherence of the next coat immediately, when the first coat is still humid by streaking or pricking it. Spray water on this fresh first coat during the first stage of the humid curing process, at least twice a day during very hot hours. • Executing the second coat : wait for the complete drying of the first coat before starting the second one. Spray water on the first coat and control the rapid process of evaporation. Execute the second coat in the same w a y as the first one but thicker ( m a x i m u m of 8/12 m m ) . Smooth it in a rounded shaping, particularly at outside corners and edges of openings. Spray water on this fresh second coat during the first stage of the humid curing process, at least twice a day during very hot hours. • Executing the finishing : wait for the complete drying of the second coat. Spray water as for previous coatings and finish with a "sarooj" or "Juss" slurry (external /internal walls), laid with a large limewash brush, in a m i n i m u m of two thin layers (like in painting), the first one being clear and the second one thicker.

Appendix 4 . - Building techniques

A . 4 . 1 . M u d blocks masonry

Near the entrance of the Fort, at a place where masons were reconstructing parts of the surrounding thick wall of the citadel, s o m e problems have been observed concerning the bonding of the m u d blocks and the thickness of horizontal joints filled with m u d mortar. M o r e care has to be taken to this bonding in both directions of the laying of the blocks (header and stretcher position), to avoid the superposition of vertical mortar joints which could create a "natural" direction for further vertical structural cracks. This could also lead at weakening the stability of the wall. The thickness of the m u d mortar joints, horizontal as well as vertical, should be more regular with an average thickness of 20 m m . This mortar should be m a d e with the same raw soil as the one used for moulding the m u d blocks but not adding straw. It could also be improved by adding some coarse sand and even some pebbles (particularly to fill the thicker joints) so as to obtain a better texture and resistance.

Appendices, p. 20

T h e m u d blocks which are used to restore this thick masonry should be laid with a slight sloping in the inward direction. This would improve the stability of the masonry which is added and built up against the old one, exactly as is done w h e n one erects a sustaining wall.

A . 4 . 2 . Reinforcing the m u d block masonry

Looking at the on restoring process of top walls of the "Bayt al-Jabal", for rooms resting against the North-West oriented rampart, or to be reconstructed on top of it, it has been s h o w n that there is no necessity to include reinforced concrete colums in the width of the m u d blocks walls to support the w o o d e n b e a m s and the loads of the terrace roofs. Such colums are not necessary w h e n the structural design of the rebuilt masonry stays in the 1/10 ratio between the thickness and the height of the wall corresponding to the safety limit of the stability for the bending stress. A s can be seen at the site, the m i n i m u m thickness of the reconstructed walls will not be inferior to 60 c m authorizing to erect them up to 6 meters high and up to 12 meters high for thicker walls (1,20 m ) .

A . 4 . 3 . Roofing systems

T h e main problems concerning roofs c o m e from the ruining action of termites and also from the lack of maintenance, leading to choose a n e w roofing structure. This can be m a d e in principle with teck beams of big section leaning on the walls and on w o o d e n corbels in the pure O m a n i style and also on stone plates (in the wall and under the beams) to suppress the punching effect. These b e a m s will be covered with "kendel" w o o d girders supporting a small w o o d e n lattice of traditional design covered with a b a m b o o ceiling on top of which will c o m e a plastic sheet receiving the tamped earth layer ( m a x i m u m thickness 2 0 c m ) . Finally this roofing system will be waterproofed with a "sarooj" plastering in two coats.

This n e w type of roofing system, if generalized, would however be very expensive. Therefore it is suggested that contacts be taken with international centres specialized in the study of w o o d in order to look for the possibility of using other w o o d species resisting the action of termites and cheaper than the teck A-3.

A great attention should be given to the design and finishing of the terrace roofing with well executed slopes (min imum of 3%) to evacuate the water in the direction of the w o o d e n gargoyles. These gargoyles will have a waterproof caping material in their gorge. T h e "sarooj" plaster will recover the connection between the gargoyle and the parapet wall which will be also protected by a good "sarooj" plaster on its internal like on its external side as well as on top (caping).

A-3 Contacts should be taken in priority with the Ministry of Agriculture of O m a n . Other well-known specialized centres in the world are : the I C O M O S International W o o d Committee, the "Centre Technique Forestier Tropical" of the C I R A D , Paris, France, the Forest Products Research Institute of the University of Kumasi, Ghana, the Kerala Forest Research Institute, Peechi, India.

Appendices, p. 21

Appendix 5 . - Suggestions for the treatment of gross structural decays

A . 5 . 1 . The reception rooms of the "Bavt al-Hadith"

i - Brief description of the structural pathology (see sketches) :

• This main room is divided by a central archway (three arches and colums) bearing the roof. • The left half part of the wall facing the entrance has totally collapsed. This has happened since 1988 w h e n a first survey was m a d e by M . Jean-Louis Michon w h o , happily, has taken a photograph which can n o w document the original state showing a nice arched door and a traditional vertical arched niche. The origin of this collapse seems to have been due to the rapid deterioration of the roof and also to the design of the structure of the wall which was partially supported by two wooden beams. • The right half part of this same wall is also damaged and presents at the top a visible outward bending and a structural crack coming d o w n to about the middle height of the niche. T h e origin of this damage is both linked with the collapsing of the roof (lack of horizontal bracing) and with a settlement of the archway which is very badly founded. Waiting for its restoration, this wall has been already propped. • The part of the roof which is staying is exposed to a rapid deterioration under the action of termites and the destroying process could be accelerated during the next raining season. • The archway presents an important separating process with a big crack under the column bearing the two first arches located in the bottom of the room. The origin of this damage seems to be linked with the general collapsing and bending process and with a threatening settlement of the first colum which has almost no footings. • The pavement of the room m a d e of tamped earth covered with a slab poured in "sarooj" is globally deteriorated. • The internal renderings in "juss" and in "sarooj" covering a first coating in earth and straw present very nice but deteriorated moulded decorations around the niches. • The joinery of the doors which have carved panels with geometric and epigraphic decoration have to be repaired. • T h e smaller reception room is in a rather good state of conservation but its roof, already attacked by termites, has to be moved d o w n and rebuilt.

ii - Suggestions for the urgent treatment (see sketches)

• Rebuilding the collapsed m u d wall will need executing a good footing in mass concrete and erecting a stone wall as basement for the m u d wall. This stone bearing wall will enlarge an actual stone basement already built by the restorers up to a width corresponding to that of the m u d wall to be reconstructed in line with the existing wall. A n arch will be included in this stone bearing wall to direct the efforts downward to the footing. T h e m u d wall will be m a d e with adobe laid up with m u d mortar, in line with the existing part of the wall located at the right side. T h e arched door and niche will be restored according to the photographic documentation. • A particular attention should be given to safe guard m e first arch which is settling. Its left jamb will be completely n e w founded by injecting plain concrete below it. This operation will be executed after having carefully cleaned, refilled (with well graduated slightly compacted soil) and levelled the earthen plateform of the pavement actually deteriorated. If this first arch can't be safe guarded, it will be necessary to demolish it carefully and step by step and then to rebuild it in its original size and shaping. But, even in this case, the consolidation of the jamb of the arch like of the pavement still will have to be done. • It will be necessary to m a k e a complete survey of the reception room of the "Bayt al-Hadith" before starting the works to document it and to mitigate the consequences of evenly further damages.

Appendices, p. 22

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Appendices, p. 24

• It is also suggested to improve the on top mechanical connection between the restored wall and the archway by using inside angle braces (at the " T " junction and also between the bottom wall and both side walls of the reception room). N o ring b e a m will be used because it is absolutely necessary to avoid a rigidity in the system and to warrant a m a x i m u m flexibility. It has been decided to use iron braces (rods) fixed in the m u d walls with big wooden nails. These braces will be no visible and so positioned on top of the finished ceiling and at the connection level with the parapet to respect the original height of the roof. • All finishing plasters, both on internal and external walls, will be m a d e after the rebuilt and restored masonry will have completely settled. This could require to wait for a m i n i m u m of 4/5 months. Solutions for plastering will refer to above prescriptions presented in the Appendix 3 "Renderings on adobe blocks walls". • The Pace-Design and Supervision Consultants civil engineering office would have to design, detail and calculate all solutions to be implemented in the restoration of these reception rooms of the "Bayt al-Hadith".

Finally, the roof of the smaller reception room will be totally rebuilt respecting the original state which presents nice painted beams with typical O m a n i motifs. It has been decided to exceptionally use teck beams (section : 20 x 7,5 c m ) leaning on the m u d walls with a span similar to that of the original roof (20/22 c m )

A . 5 . 2 . The small mosque extra-muros

i - Brief description of the damage (see sketches):

The main objective is to safe guard the mirhab which is n o w exposed to an imminent collapse.

• T h e mirhab wall presents a very important outward bending and is already separated from the right side wall of the mosque (from inside view). T h e origin of this damage is due to the collapse of the roof which has totally suppressed the top wall horizontal wind-bracing and also to important and frequent ground vibrations resulting from the heavy road traffic nearby and along the mosque. T o prevent the threat of collapse, the roadside mirhab wall has been already propped to sustain it. • T h e mirhab wall presents an important erosion at its bottom part both inside and outside. Outside, this erosion comes from unappropriate water surface drainage and also from rain splashing on a too hard ground surface material (asphalt). This plateform has to be totally remade to correct the sloping direction of the drainage. • T h e left side wall presents an advanced erosion but could be safe guarded and restored. It is urgent to m a k e a complete architectural survey to document the presence of two small niches and vertical ventilation holes (now refilled with m u d ) on its top part. • The right side wall is very deteriorated and separated from the mirhab wall. It has to be carefully demolished and then rebuilt. • The main front wall of the mosque (entrance façade) has been totally destroyed. • T h e access plateform to the mosque is partially collapsed and it is very difficult to document the past existence of small precinct walls creating a traditional entrance courtyard.

ii - suggestions for the urgent treatment (see sketches)

• Consolidate the mirhab wall by providing a temporary support for both sides (only the outward side has been propped by n o w ) . This must be done very carefully to safe guard the mirhab which has to be conserved in its actual state before restoring it • It is suggested to explore the nature and the actual state of the foundations of all walls which would be conserved and to consolidate them by injecting plain concrete if necessary, step by step, at a m i n i m u m depth of 30/40 c m .

Appendices, p. 25

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Appendices, p. 26

• First, it will be necessary to restore, carefully and step by step, all the eroded bottom part of the mirhab wall which will be conserved (a min imum of 1 meter long, both sides of the mirhab). This restoration needs to rebuild this bottom part in m u d blocks, but progressively, in successive elements and alternately. • W h e n all the restoring works described above will have been correctly executed, it will be possible to carefully demolish the masonry in m u d blocks on both sides of the mirhab wall, conserving a min imum distance of 1 meter from the mirhab, both left and right side. A "key" design will be made to ensure a good further connection between the n e w and the existing m u d blocks work. The footings of this demolished part of the mirhab wall will have to be consolidated by pouring some mass concrete at least at a min imum depth of 30 c m below the existing ground level. These n e w footings will bear the reconstructed wall both sides of the mirhab. N o mechanical tools will be used to dig the trenches in order to suppress vibrations. All the work will be hand-made. • Executing new fondations for the right side wall which will have to be completely rebuilt and connected with the m u d blocks work of the reconstructed right side part of the mirhab wall. • All the reconstruction of demolished walls will have to be executed simultaneously and uniformally in order to warrant an homogeneous settlement of the n e w masonry. This reconstruction will be done slowly with a m a x i m u m of 6 layers (about 1 m high) of m u d blocks at the same time. • All rebuilt walls will have a small stone basement erected up to a min imum height of 30 c m above the ground level before starting the m u d blocks work. For parts of walls which are restored, it is suggested to build an outer stone plinth up to the same height, in the continuity of this adjacent stone basement of the reconstructed walls. • The connection and the stability of the left part of the rebuilt mirhab wall and of the left side wall of the mosque which will be restored will have to be executed very carefully with an appropriate m u d blocks work. If necessary, a bracing system on top of the restored ceiling, at the left inside angle, of the same nature of this previously described for the reception room of the "Bayt al-Hadith", could be realized. • The vertical outer side shaping of the conserved part of the mirhab wall, actually temporary propped, will have to be done simultaneously with the reconstruction of the left and right side part of the mirhab wall (to allow a c o m m o n settlement of all masonry). This outside shaping will be a buttressing masonry in m u d blocks, built up with a slight outward rounded shaping. This buttressing masonry will have to be erected step by step on n e w footings in mass concrete. T o facilitate the removing of the temporary props without any risk of collapsing, it could be necessary to build two temporary outward buttresses in m u d blocks (orthogonally and at both extremities of the conserved part of the mirhab wall) or to stengthen the props at the top part when the outside buttressing masonry of the mirhab will progress from the bottom to the top. • The main entrance wall of the mosque (or main façade) will be also rebuilt on n e w footings and when the courtyard plateform will have been consolidated. The design of this façade and its decoration will refer to the local typology of the small mosques existing in the Bahla citadel and Oasis. • The plateform between the mosque and the road will have to be totally remade to properly evacuate the run-off of the surface water. A gutter will be realized at the ground level, at a minimum distance of 1,5 meter from the bottom of the wall of the mosque. The slopes of this plateform, both from the wall of the mosque and from the road will be directed to this gutter. The top finishing of this plateform will be m a d e with gravel to reduce the splashing and to allow the good evaporating process from the ground. • All finishing plasters, both on internal and external walls will be made after the whole settlement of the rebuilt or restored masonry. This could require to wait for a min imum of 4/5 months. Solutions for plastering will refer to above prescriptions presented in the Appendix 3. "Renderings on adobe blocks walls". • The Pace-Design and Supervision Consultants civil engineering office would have to design, detail and calculate all solutions to be implemented in the restoration of this small mosque extra-muros of the citadel.

Appendices, p. 27

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Appendices, p. 29

In the short term the bus shelter located nearby the m o s q u e should be removed to a reasonable and unconspicuous distance from the Fort. In the middle term, one should consider diverting the main road which n o w runs cross the Bahla oasis, supporting an important traffic probably responsible for the deterioration process on Bahla site.

Grenoble (F) - Geneva ( C H )

June 1995

Appendices, p. 30