11th rNTERNATIONAL BRICKlBLOCK MASONRY CONFERENCE

TONGJI UNIVERSITY, SHANGHAI, CHINA, 14 - 160CTOBER 1997

METHODOLOGICAL HYPOTHESIS FOR INVESTIGATING INTERVENTION: THE PROBLEM OF THE DAMPNESS IN THE

"SASSI" OF MATERA

Antonella Guida I

1. ABSTRACT

The complex problem of the constructed environment in the "SASSI" of Matera is developing into a more pressing manner than the more articulated one of the habitability and of the environmental comfort. A vigilant knowledge of the urbanized context ofthe "SASSI" and ofthe typological articulations of the living system has addressed the research on the principal ways of propagation of the dampness inside the rocky walls of the natural hollows "IPOGEI" or of the built environments. The research analyzes and correi ates the different methods of measurement of the dampness inside the wails and it is articulated in laboratory analysis and experimental tests 'in situ'. The analysis of the "typologies" of the actual environmental degrade in the "SASSI" has underlined different causes, which aren't parametricable according to the current literature, but they are exactly correlated to the origin of the phenomenons of dampness relieved. The investigation made on a pattem' ( "IPOGEI", with a housebuilt in front of it, "with a court", with a fenced atrium - it forms a "unity neighborhood") aims to the formulation of methods for the intervention in vrder to the evaluate the environmental and hygrometric conditions, to restore the health conditions of these unities, with the support of attentive and detailed measuring and evaluating investigations of such phenomenons of dampness and technical-environmental degrade. Such techniques will be a fundamental support for each type ofthe project intervention aimed to restore and to keep the "SASSI" of Matera.

Keywords: Methods ofmeasurement; Dampness; Walls; Typologies; Degrade.

IProfessor, Department of Architecture, Planning and Infrastructures for Transport, School of Engineering, University of the Studies of Basilicata, Via della Tecnica 3, 85100 Potenza , Italia.

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2.PREFACE

The "Sassi" are the two characteristic districts of the city of Matera in the south of Italy which date back to the Prehistoric age. The oldest document which quotes the word "sasso" (rock) with the meaning intended to be an "inhabited stoney district" is from the year 1204 . The Sassi from the Prehistoric through to the Hellenist and Roman ages were partially inhabited in isolated areas. It remained a densely inhabited placc up until after the Second World War and then it was completely abandoned. For the last twenty years there has been a slow and partial repopulating of these districts.

3. INTRODUCTION

In the last few decades the building patrimony, whatever its location, thanks to the collective conscience being made aware, has become an object of study and of recovery for the historieal importance ofthe buildings as well as for the position and the functional role it may develop inside the urban web. It is even more important for the safeguarding and preservatioi1 of a direct valid testimony of the technical knowledge of past eras, as well as for its role in the cultural evolution of humanity. The experimentations in t.'te field of preservation have therefore been aimed at individualizing criteria from surveys and appropriate methods, which have lead to a better knowledge ofthe building construction, in order to optimize the interventions for recovery. This work is intended to be a contribution to such research, a deeper study of the calcareous rock, as this is, regarding the particular typology of the "Sassi", the primary element wIDch constitutes the buildings. In particular, the ways of the diffusion of water inside this rock were studied. Trying to identify the causes of dampness present in any location based simply on the personal impressions of the observer, without carrying out precise measures which can determine its topographical distribution has often lead to incorrect interpretations which thus lead to the adoption of methods of intervention which do not "cure" very well and may even be damaging or useless. This consideration appears fundamental for the "Sassi" ofMatera in which there is a noticeable complexity of constructive typologies which are not a1ways reportable as normed "types" or having conditions of extremely serious dampriess. Infact from data compiled by the Commission of Study of the City and the Surrounding Land of Matera in 1953 [1], it results that out of a total of 3,325 existing houses in the Sassi: -1143 houses are in caves or partial!y in caves; -848 houses have as a cover the rock, the road, the road with sewerage, difIerent types of cover; -1,056 houses are below road levei; -2,140 houses show problems of permenent 01' temporary dampness; -2,375 houses have only one solar exposition. Adding these conditions of definite potential degradation to a reality which has seen Ilbanrlonment for more than thirty years with further hygienic sanitary decay, we

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have , today, a general picture of the old areas in which the dangerous forms of astatism principally due to the lack of maintenance are obvious. The notable variety, complexity and originality of the Iiving typologies underline the atypical situation in which the different causes of dampness (constructive, accidental, meteoric, from condensation and capillary ascerit) are often not immediately identifiable, aI~o due to the almost always overlapping oftwo or more causes. It is c1ear and evident that the primary intervention shouJd be aimed, together with structural consolidation, at the e1imination of dampness in the "Sassi" rooms and to regulate the microclimate, so as to be able to ensure the final users of these rooms the best conditions of comfort. The analysis of a method of restoration was carried out on a construction representative of one of the above mentioned Iiving typologies. The chosen house has a courtyard partially built and partially dug out of a cave with a small entrance in front of it. The first part of this construction is made of walls of blocks of Iimestone rock, probably dug out of the cave which constitutes the second part of the construction. It is this from the cutting away of the tufa from inside the cave, which is the recurring constructive typology that clearly shows us the origin of materiais used and the absolute penetration between the excavated rooms and the constructed ones constituting a homogenous "continuum" of materiais. Inside this house there exists no other aperture apart from the maio door above which is an' opening to allow solar iIIurnination. In this house tests were carried out to measure the rei ative dampness and temperature to study the microclimate, and the measurements were taken of the dampness present in the rock and walls to understand the phenomenon ofthe diffusion ofwater in these materiais. Apart from what the RD. no. 2232[2] and the D.M. 20/11/87 [3] order, the legislation in these fields of investigation is non-existent, and so it is necessary to redo tests using methods already known and applied which have given particuJarly reliable resuJts, to measure the dampness in the rock. For this, the a weighing method was used [4,5,6,7].

4. QUALITY ANO QUANTITY SURVEYS - DIAGNOSIS OF THE CAUSES OF DAMPNESS.

The place chosen (photograph 1 and 2) was built between 1500 and 1700 and, from the presence of rooms, fire-place and trough orie assumes that it was Iived in by people and animais (a typical situation ofmany ofthe houses ofthe Sassi). The hypogeum in question was dug directJy out of the Iimestone rock and partially lay under a road (another typical situation of many of the houses in the Sassi). One does not find the presence of water (cistems, pipes etc) in the vicinty. The levei on which it Iies is at an illtermediate height on the slope facing the "civita" with at least one built levei above and approximately three leveis below.

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Photograph D.l

\ '

Photograph D.2

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4.1 Quality survey.

The first guality survey was carried out following the method indicated in [6] and the diagnosis results are reported in [8]. From the survey one can deduce that the dampness is on the surface and probably deep, accompanied by mold, dark spots and slight corrosion in a few aí"eas. It has developed from the bottom towards the top, located more or less intensely in a rather large area. It is a chronic condition which worsens in the case of rain which also causes water to drip from the ceiling. This manifestation of dampness is mainly due to infiltration of meteoric water.

4.2 Quantity survey.

The guantity survey was divided into a stage of identification of the physical, chemicaI and thermophsical characteristics of the limestone constituting the hypogeum, a stage of evaluation in the laboratory of the behavior of the material in relation to the migration of the dampness and a stage of on site measuring of the dampness ofthe walls and ofthe environmental microclimate. In the first stage, in the laboratory a series of physical characteristics were established which qualify the material, its average values are reported in table 1 (for details and ways of testing see [8].) : real volume mass, apparent volume mass and porosity percentage. Also reported in table 1 are the percentages of the main components making up the limestone rock ofMatera [9] and the value of the average thermal conductivity obtained in [10] for the tufa of Gravina which possesses physical characteristics very similar to the ones of the material here being tested.

Real mass volume 2.6751 (g/cm3)

Apparent mass volume 1.4535 (g/cm3)

Porosity percentage 45.3% CaC03 95% MgC03 1.7% S03 0.1% Dry material conductivity real denso = 2.652 (g/cm3

)

app denso = 1.444 (glcm3)

0.56 (W/rnK)

Table 1 - Physical, chernicaI and thermophysical characteristics ofthe material.

The value of porosity at 45.3% is slightly inferior to the average value of 46.2% which was found on 33 tufa stones of sandstone from the Puglia area [10]. These values confirm the notable porosity ofthese types of material which are particularly sensitive to the diffusion of water. The fairly well contained conductivity and the notable mass volume indicate the good characteristics of the material as regards the reduction of thermal dispersion and the increase of environrnental comfort particularly i~ summer. In the second stage [8] tests of the absorption of water (table 2) were carried out initially for total immersion on 10 specimens of 5x5x1Ocm dimension initially dried

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out in an oven [lI]. The average value of the coefficient of absorption resulted equal to 23.8% and is stable from one hour onwards, with a difference ofless than 1% from the first weighing to the second. Tests were carried out on the same specimens for capillary ascent (table 2) [12]. From the asymptotic value of the weight reached after an interval of approximately 41 minutes the average values of the absorbed mass per unit of the surface (2. 8470gr/em), of the coefficient of the capillary absorption (22.4%), and of the maximum height reached by the water at 9.83 cm were established. A non standardised test of the migration of water in an orthogonal horizontal direction. was carried out, which allows us to understand another parameter useful in the planning of a "drying" system of the walls. The tests were carried out on 3 specimens of IOxlOxl5 em dimension, First of alI, four sides of the specimens were impermeabilized with silicone, then one of the untreated faces was placed in contact with a Icm layer of filter paper held vertically and constant1y soak:ed in water. The test finished when the face vertically opposite this one became wet with the water. The parameter measured (on 9 tests in total) was the speed ofhorizontal migration of water equal to 0.03Immls.

Coefficient of total absorption Total mass absorbed Percentage porosity Coefficient of capillary absorption Mass absorbed per capillarity Maximum height reached by the water Velocity ofhorizontal migration ofthe water

Table 2 - Test results ofthe migration ofwater

23.8% . 0.33 (gr/cm3)

45.3% 22.4%

2.8 (gr/cm2)

9.93 (cm) 0.031 (mmls)

In the third stage tests for the evaluation of the dampness present in the rock or in the walls ofthe hypogeum under examination using the weighing system were carried out. This is the best way regarding both precision and repetition. The method used for the extraction was the one prepared by BRE which requires a core boring pipe and a dri11 [4]. In order that the operation of extraction would be as indestructive as possible, a pipe was used for boring, created especially for this purpose in steel inox with an internal diameter of 14mm and 30cm long at the tip of which a slot cutter of the same diameter was welded; the speed of the dri11 never exceeded 100 revolutions per minute so as it would not heat up and evaporate offthe water present in the rock. To have as complete a picture as possible of the house, idealised vertical and othogonal plans were traced on the perimetric walls ofthe same house (plans from A to I, enclosure 4). Three marks were made on these plans at a height of approximately 0.5, 1.5 and 2.5 metres from the floor. In these points extractions of the rock were tak:en at various depths (surface, 5cm, IOcm,15cm,18cm). To avoid excessive heating of the rock near the advancing pipe, drilling was carried out to within lem of the required depth and, after a short period of time (2,3 minutes) useful for the cooling down, the drilling was continued to mak:e the extraction. The

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samples taken were ir.lmediately placed in porcelain pots which were immediately sealed with parafilm (plastic vapour impermeable material); this W&S followed by the drying out phase in an oven at J05°C and then the weighing using centesimal scales. Tests were a1so carried out in another house near the first one (photograph 3) in which from the visual quality survey there did not appear to be an obvious infiltration of meteoric water, in order to establish a so called "physiological dampness" ofthe houses in the Sassi, that is to say an elevated dampness but not one created by particular causes. In the first hypogeum measurements of the rei ative humidity and internai tempera~re were taken for approximately six months, from April to October 1995, with the aim of understanding the existing microclimate. The results are reported in detail in [8]; we report here this data and the basic considerations to establish a diagnosis ofthe main causes of dampness in the hypogeum under examinarion.

Photograph n. 3

4.3 Diagnosis.

The quality and quantity surveys show that there is surface dampness spread throughout the area; on average about 9.1 %, a higher amount compared to the ~ dampness ofthe'second house which is egual to 5.4%. The cause is the migrarion of water present in the rock to the surface, which cannot be carried away by the stagnant air of the house as it contains elevóted relarive humidity (average value

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measured around 80%). There is also the presence of water, in the profundity of the walls, located in a strip of about 3 metres coinciding with the load which passed over the roof of the hypogeum due to the infiltration of rain water. The dampness in such areas goes from a value of about 18% (I8cm deep and l.5m high from the floor) to 5% (same depth and a height of OAm from the floor). Moreover the surface dampness, in these points, also reaches values of 35%; which is due, as can also be observed visually, to the intense action of the water, which has changed some of the properties of the tufa, making it more permeable and flaky. Finally, there is also present capillary ascent but in a slight and located form of infiltrated water absorbed by the floor and passed on to the walls.

5. METHODOLOGICAL HYPOTHESES FOR IMPROVEMENT.

As has previously been diagnosed, there are two causes for the dampness of the hypogeum: I) infiltration of rain water from the vaulted roof, above which passes the road called ~San Giovanni Vecchio"; 2) general surface dampness due to the stagnation of very damp air, at the limits of saturation. The first cause is predominant because of the palticular porosity of the calcarenous rock which favours the infiltration ofwater both in profundity and on a good part of the surface of the supporting walls. The second is a direct consequence of the first; the water contained in the walls by evaporating goes into the air. The particular geometry of the hypogeum, plus only one opening, establishes a stagnation of air bécause ofthe lack of circulation. The firstjob to carry out, therefore, is the elimination of the cause of infiltration, by impenneabilising the road above prior to the structural consolidation of the vault below (barrel-vault of the hypogeum) and the possible emptying out of the sides of the vault and the substitution of the material with a lighter insulating one. If necessary a reinforced covering ofthe vault wiIl be carried out. Once the cause of infiltration has been eliminated, the problem remaining is that of the "drying out" of the walls, the floor and the ceiling of the hypogeum to at least bring them to the leveis of surface dampness near to the pysiological one which is around 5%, higher than the one in the laboratory which does not reach 1.1 %. The reduction of the dampness in the waIls may be obtained through a forced ventilation with air that has extemal conditions or if necessary treated (dehumidified or heated up). In the first case it should be noted that the introduction of the air should be carried out in the hours in which the dampness in the air is on average lower and has a longer time; in the second we definitely have a higher cost due to the unit of treatment and its higher energy consumption. Another problem that arises is the left hand side ofthe hypogeum (along with other problems) which is made up of rock and it is not possible to establish its thickness; one may therefore hypothesize that the drying out, in a horizontal direction must arrive at a reasonably conventional depth (which may be around I metre). It is obvious that only a real experimental intervention, which one intends to carry out, with a later verification of its effectiveness, can give

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more precise results. . The hypothesis of intervention, for a specific case, but extensible to a much wider series of cases, begins with the assumption that having seen the obvious causes of dampness, the only valid operation to be carried out with definite effectiveness is to apply a more or less articulated "system ofventialtion". The assump"cion considers such ventilation as the most natural hopeful solution of ali interventions including those not rnonitored scientifically, and leaving out the possibility that it may be backed up by machinery for the forced intake and circulation of such 'air' . The SYSTEM must guarantee an essentially natural ventilation from the outside, which continues throughout the day and the year. One ofthe countless methods ofintervention forseen in these cases was chosen to be carried out and it is concisely described as follows . (photograph 4) To carry out the ventilation a gap between the current floor and the eventual final one will be created at a height equal to about 20cm. The gap will be made using an orthogonal frame of 'muricci', halfbrick walls, leaving in communication air spaces to form, on which will be lain a tiled boarding, the insulator, the cement creed with an electrowelded mesh to divide the weight and on top of everything the tile finishing. The system of forced ventilation will be carried out by preparing a system to take in air from the front of the gap through openings in the facade or from the floor of the courtyard, and to distribute the air, to the walls that need drying out, via small openings of an appropriate size placed along the whole perimeter of the hypogeum. The extraction of the same quantity of air put in will be carried out via a system of aspiration placed in the upper part of the front facade of the hypogeum (the light opening element above the main door in the entrance area). The ' drying out' time depends on various parameters: on the work beforehand or rather on the air, on the number and size ofthe openings and on the characterisitics of the ventilators that expeí and suck in the air. When this first step of accelerated drying is finished, the perimetric openings will be preserved and naturally circulating will be guaranteed through the front grills and by a vertical canalization which expels extemally (positioned at the bottom using a pre­existing chimney stack). The same system of ventilation spaces under the floor can be used to insert various canalizations and to distribute hot\cold air in order to maintain a stable condition in the house. The presence of constant natural and\or forced air will in time help eliminate ali forms of dampness which can form in the rooms and on the surfaces of the walls due to the particular rock formation . (photograph 5) Before drying out the walls, it is necessary to carry out the restoration work of the hypogeum. From the enclosed photos 9 and 9A, the damage caused by the dampness and abandonment are clearly noticeable; spots ofvarious colour and shape, growth ofmould and corrosion in various points ofthe rock etc. It is therefore necessary to intervene with a clean up, with the removal of the corrosive parts, and the repair of the most jeoparised parts, with possible consolidation inserting rods in the walls and the creation of new supporting arches. The drying stage, as calculated in our case, should last approximately 8.5 days working continuously. It would be advisable, in order to guarantee the migration of the water towards the surface, as well as for logistic reasons, if the operation were to

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be limited to 12 hours per day with a 12 hour break. At the end of this hypothetical time extractions could b .. taken to check the dampness still present in the walls.

Photograph n. 4

Photograph n. 5

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After the drying out stage, the finishing touch work begins. As regards the walls and the ceiling the front part of the hypogeum which 1S not yet in jeopardy may be left as it is after a simple smoothing down and clean up prior to being treated with a stabilizing material, which cou!d be a transparent resin which very slightly changes the colour of the natural stone; whilst on the posterior parts a course of treatment could be applied using macro-porous plsster as shown in the sample photograph number 6.

Photograph nO 6 - Macro-porous plaster

This is made up of inorganic binders of the traditional kind (cement, white cement, mainly hydraulic lime) used either individually or rnixed together. Their composition is made up of cells which have a diameter that can reach 200 microns communicating with each other through a tight network of micrpores which ensure capillary transport of water through quite large pores (macropores) within which there is the formation and the consequent expulsion of water vapour. The best way in which this type of plaster works has been shown to be directly conneeted with its thickness. Treatment using this type of plaster could have various advantages, amongst them the transportation of the dampness from the rock direct1y into the ventilated air, the lack of formation of mould or spots due to the lack of water present in the surface, the lack of swelling and peeling of the plaster due to the deposition of salts transported by the water through pores in the plaster which must be large enough to guarantee a suffiiciently wide distribution. An obvious result of this study up until today, is that in our case rising damp is a phenomenon of secondary importance, however the precautions quoted above (ventilation, macroporou!' plaster) are perhaps the most efficient to eliminate also this type of dampness which could occur as a phenomenon in places in the Sassi

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which have a similary typology to the one under examínation. The barrage systems, of a mechanicaI or chemicaI type, as regards the capillary ascent [13] are not effectively applicable as the walls of this type of hypogeum are of a notable thiclmess, are very irregular and at times the thiclmess is indeterminate (infinite theoric thiclmess).

6. REFERENCES.

1. R. Mazzarone in: Commissione per lo studio della città e dell'Agro di Matera, UNRRA-CASAS Roma 1953; "Sassi di Matera, un contributo alIa comprensione della vicenda storica dei Sassi", Prof. Manfredi Tafuri, Edizione BMG, Matera, 1974.

2. Regio Decreto nO 2232 deI 16.11.1939, "Norme per I'accettazione delle pietre natural i da costruzione.", G.U. nO 92 supplemento de! 18.4.1940.

3. Decreto Ministeriale dei 20.11 .1987 pubblicato sulla G.D. nO 285 supplemento dei 5.12.1987.

4. P.M. Trotman , "Diagnostic methods for dampness in Walls, Seminar and workshop on rising damp " , CNR- Progetto Finalizzato, Bari ,17/18 Settembre 1991.

5. M.H. De Wit, "Measuring methods of moisture in solids, Seminar and workshop on rising damp" , CNR- Progetto Finalizzato, Bari ,17/18 Settembre 1991 .

6. C.Aghemo, E. Cirillo, I. Fato, M.Filippi, "L'umidità nelle murature - Una metodologia di indagine.", Recuperare n.7, PEG, Milano, 1991.

7. C.Aghemo, G. Alfano, E. Cirillo, F.R. d'Ambrosio, I.Fato, M.Filippi, M. Stella, "L'urnidità ascendente nelle murature - Proposta di protocolli.", Recuperare n.2, PEG, Milano, 1992.

8. M.Cannarile, "TI Risanamento da umidità dei Sassi di Matera: diagnosi ed ipotesi di intervento su un ipogeo.", Tesi di Diploma in Ingegneria dell' Ambiente e delle Risorse, Università della Basilicata, Matera, 1~95 .

9. G. Romaniello e G. Zuardi, "Conservazione della muratura dei Sassi di Matera: i materiali, la struttura ed iI consolidamento mediante iniezlOni.", Tesi di laurea, FacoItà di architettura, Pol. di Milano, A.A 1992/1993.

10. IRIS-CNR , Quademo monografico nO 10, "Le pietre da costruzione di Puglia: i1 tufo calcareo e la pietra leccese." ,Bari 1991,

11. CNR, Centro di studio di Milano e Roma, "Sulle cause di deperimento e sui metodi di conservazione delle opere d'arte." I.C.R. Istituto Centrale deI Restauro, Raccomandazione Normal 7/81 : assorbimento d'acqua per immersione total e -capacità di imbibizione.

12. CNR, Centro di studio di Milano e Roma, "Sulle cause di deperimento e sui metodi di conservazione delle opere d'arte." I.C.R. Istituto Centrale dei Restauro, Raccomandazione Normal 11/85: assorbimento d'acqua per capillarità­Coefficiente di assorbimento capillare.

13. C.Aghemo, G. Alfano, , M.Filippi, M. Stella, "L'umidità ascendente nelle murature - Tecniche di intervento.", Recuperare n.2, PEG, Milano, 1992.

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