Bonaldi (Australia) Pty Ltd

RESEARCH

Testing actual building façades for weathertightness (wind and rain)

There are three ways of doing this:

1 AS/NZS 4284 2 AAMA 501.2 (USA Code) 3 AAMA 501.2 with Australian modifications on tall buildings

1.0 WHY AND HOW TO USE AS/NZS 4284 (Testing building facades)

1.1 THE PRINCIPLES OF PREVENTING WATER ENTRIES AND SITE TESTING

This standard has been adopted by both Australia and New Zealand. It not only covers water entries but also air infiltration, testing against structural performance and earthquake.

The History of the principles of preventing the entry of water through the cladding of a building is the creation of the Pressure Equalisation Drained Joint System. (PEDJ)

The basic development of this is described by me on page 7 of my first published book “Detailing for water: Why do buildings leak?” published in 2007 and in even more detail in the “2014 Supplement” on pages 29-31 and was outlined in the 10 seminars organised by the Institute of Architects Australia in 2007 (650 attendance) plus the three seminars held in NZ 2010 (700 attendance) organised by the NZ Institute of Architects and sponsored by Ministry DBH Wellington NZ. I also stress the point that the Canadians made use of the 17th century “gas formula” by Robert Boyle (read this paper).

The investigations into leaking facades of the cladding and curtain wall type started in Europe in the 1960s.

Birkeland O. “Curtain walls” handbook 11B, Norwegian Building Research Institute 1963

Garden G.K. “Rain penetration and its Control” CBD40 National Research Council Canada 1963

Garden G.K. “Joints between Prefabricated Components” Conference in Montreal Canada 1963

Garden G.K. “Look at Joint Performance” CBD97 National Research Council Canada 1968 NRCC

The Architectural Aluminium Manufacturing Association of Chicago published a handbook on the subjects showing its application on curtain walls in February 1971.

(left) is the 1973 Canadian report on weathertightness of Canadian buildings & talks about PEDJ.

The research by the Canadians in their Ottawa offices was picked up by the CSIRO in Highett Vic. Australia in the early 1970’s and was demonstrated on concrete façade panel joint mock-ups on their ‘Open day’ in 1972 and the CSIRO Book “Wind driven rain and the multi storey building” published 1972.

In 1975 CSIRO published the booklet “The SIROWET Rig” by N. Brown and E. Ballantyne.

At that stage, all the research at the CSIRO was also passed onto BRANZ in NZ. BRANZ themselves published books on the application

for pre-cast concrete façade designs at the same time. (Available from the library of BRANZ in Wellington NZ)

In 1975 the CSIRO through R. Couper held seminars in all major cities in Australia to show their research on water entries into buildings and most of their (CSIRO) seminar slides are now contained in other author’s books and are referenced. It was at that stage that the architectural profession was made aware of the design of joints in facades as being of the open rain screen type adopting the research on the pressure equalisation drained joint methods.

Then in February 1990, the CSIRO published TR 90/2 “Specification for the Performance Testing of Building Facades by the SIROWET Method” This was known to BRANZ and to Standards NZ.

In 1991 BRANZ published their Case Studies “Drained Joints” with the assistance of Noel Brown (ex CSIRO). At that stage Noel had retired from the CSIRO and became part of my firm working for another 15 years in establishing site testing and viewing shop drawings of fabricators and doing quality assurance inspections in workshops.

On 30 June 1992, the CSIRO updated TR 90/2 and issued TR 92/6 that became the draft of AS/NZS 4284:1995. This Draft was circulated in Australia and in NZ by Standards Australia and by Standards New Zealand on the 1st of July 1993 and for public comments from the industry on the 31st of August 1993. The Code was issued and brought into force in Australia & New Zealand in 1995, then was amended in 2008.

The author first applied the PEDJ system on the curtain walls of the 35 storey AMP State offices in Perth WA in 1973. Photograph below, left. The photograph to the right is that of Nauru House Melbourne being a 4mm sheet aluminium over cladding of an existing concrete building built in the 1970s. Photo shows the over-cladding under construction.

Since 1973 the author has used it on many office buildings and as over-cladding onto existing buildings with water entry problems. Bonaldi (Australia) Pty Ltd have used the principles on the 55 storey Nauru House in Melbourne Vic. as the over-cladding to a building that had concrete cancer problems as well as minor water entries.

(Figure left) is the PEDJ designed detail by the author for the curtain wall of AMP Perth W.A. It shows the PE (Pressure equalisation) cavity between the concrete

columns and the adjoining curtain wall jambs and its associated building maintenance unit track.

In the Nauru Tower Melbourne case, we took models into the Monash University wind tunnel as well (and at 1 Hz) with a scaled testing prototype and then had a full-size prototype tested on site to AS/NZS 4284 (0.33 Hz). That showed that the 4mm solid aluminium cladding, ventilated correctly to the ‘Gas formula” (Robert Boyle 1627-1691) resulted in a Zero wind loading on the sheet aluminium cladding itself.

PEDJ system is not to be taken to be that of the NZBC ‘drained cavity’ on the bottom of a façade going around all the faces of a building and being a single cavity for the height of the 10m applicable to E2/AS1. The wind pressures on a building vary as to their height and orientation and some facades may be under negative wind loadings and any cavity that may drain leaking water to

Design by Peddle Thorp Melbourne. Facade detailing by Bonaldi (Australia) Pty Ltd including Quality Assurance

the bottom by gravity is in no way becoming a PE cavity at all. Each floor and each change in direction on building corners needs to become the enclosed drained cavity and each of such volumes need to reach equalisation via the slotted ventilation and drain holes on the bottom of that specific cavity. We developed a computer program incorporating the Boyle gas formula to establish the slot area related to the wind frequency of both 0.33 Hz and the 1 Hz.

Noel Brown of the CSIRO developed the SIROWET testing rig (previous page) to be taken onto existing buildings and test to AS/NZS 4284 way back in 1975 and he did quality assurance checks on the Melbourne ANZ tower.

Tailor-made rigs (to the left) can be used and extending to two or more storeys in height. The photograph is one of our tests on a 35-year-old building that showed leaking cladding and windows. A concrete panel system with aluminium framed windows.

Sealants deteriorated and the design was a single seal system, when it was thought to be a PEDJ design that had been CSIRO tested but was not built to that design. The rig on the left was built and tested by Ian Bennie and Associates Melbourne. It included converting the single seal joint seal into a proper PEDJ system and with degradation tests by removing sections of the new

sealants as well.

Refer to my book “Supplement 2014” on page 30 for conversion detailing of single seals into PE (pressure equalised) systems.

The author was a government appointed member of the technical advisory committee to the building research section of the CSIRO from 1964 to 1988. A period during which all the Australian development of the PEDJ system took place.

Left: Robert Boyle, founder of the ‘gas formula’ that is part of the Canadians’ 1968-1973 research basis and we built it into our own computer program software.

1.2 Weathertightness explained: -

Their basic research was based on the old ‘gas formula’ created by Robert Boyle and was then applied to the cladding design used on the twin tower World Trade Centre in New York under their new building code for the City.

At the time, the two towers were under construction, the author had been given a scholarship by the Royal Australian Institute of Architects in Australia (1967) to research modern building codes. During the period of my research (1968), I was based in both Ottawa, Canada and New York and met the individuals who were developing the PEDJ system in Ottawa. This included the New York World Trade Centre’s architect, Yamasaki and the structural engineer, Leslie E Robertson, both I interviewed in New York at that time.

I adopted the method, first time, in the façade design of the AMP office tower of 35 levels in St. Georges Terrace, Perth (WA) in 1973 - 75. (See photograph and detail on previous pages)

1.3 Is it Weathertightness or is it not?

When the New Zealand Government appointed Price Waterhouse Coopers to investigate the common belief that the country was full of “leaking homes” and that was shown in the PWC report of 29 July 2009, nobody took any action. Now it has advanced into the High Court of New Zealand in Auckland as a case against material manufacturers, when nobody has yet done a façade test to PROVE it as being a leaking building. Until that is proven by testing to at least the standard I describe in this paper, NZ housing is suffering from winter period CONDENSATION, NOT lack of weathertightness. Houses were built with Council Consent and to the applicable

details under the NZBC, on outdated 20th century documents for the stucco and cement sheet claddings with or without the ventilated batten cavity now demanded by the current Code.

1.4 The definition of a pressure equalisation and drained joint system was defined by the author in 1989 as follows: -

“When two chambers are coupled by air passages of sufficient capacity and area so that when the pressure is varied in one chamber (the outside of the building) the pressure in the other chamber becomes equalised”

This principle is used in drained joints where by pressure equalisation of the drainage zone (the cavity) to outdoors, water that penetrates the outer rainscreen of the joint, into the drainage zone, is able to drain by gravity to outdoors again without coming in contact with the inner air seal.

A drained joint is made up of three components: a rain screen at the outdoor face, an air seal to indoors and a drainage zone {Note 2} between the outer rain screen and the inner air seal. The drainage zone being thereby pressure equalised to outdoors by openings in the rain screen and under protected conditions (shielded) to allow the outdoor water flow not to cover over the opening.

The rain screen and drainage zone are required to prevent water from reaching the inner air seal, {Note 3} which carries the outdoor to indoor air pressure differential. The drainage zone carrying the flow of water that may have entered the zone should be having an adequate fall {Note 4} to outdoors to allow the gravity flow to take place and avoid ponding and any water build-up thereby flooding the drainage zone space and by doing so bringing the inner air seal in contact with water.

Bonaldi (Australia) Pty Ltd Dec. 1989

1.5 Explanations of the details in the above “Canadian Rules”

It is of most importance to relate these rules to the interpretations given by BRANZ in their Study of 1991 and which was supported by Noel Brown, a retired scientist of the CSIRO and who developed the ‘Siro Rig’ to test facades and which is now incorporated into AS/NZS 4284.

In the above set rules established by research carried out by the Canadians, the vital parts in respect to the cavity {Note 2 above}, are the conditions of items {Note 3} and {Note 4} that need to be achieved for PEDJ systems to conform to item {Note 1}.

{Note 1} For the cavity to be reaching the same dynamic sequences of pressure changes that take place in the wind onto the facades, the pressure builds up and following release needs to follow that of the wind and at the cycle of some 1 Hz (one complete cycle within one second).

This means there are volumes of air Canadian diagram to pass into and out of the cavity based on the mechanical engineering formula of ‘Gas pressure by Robert Boyle’ (1627 – 1691). (This gas pressure formula plays the basic role in the mathematical estimation of the air flow in and out of the cavity. Whilst this is not mentioned in the Canadian nor the BRANZ nor the CSIRO reports, in fact it is the basis of all the designs of the PEDJ systems.

Then the openings through which the air needs to pass need to accommodate velocities that relate to the shape and roughness of the opening, all that within the set time frame of one complete cycle. This becomes a complex calculation that can be best resolved by the computer program we have established in our organisation. Because the CSIRO ‘Siro wet’ testing procedure is of a mechanical nature and forms part of AS/NZSA 4284, the cycle for such testing is based on one complete cycle over 3 seconds (0.33 Hz). More details on this can be found in our publication “detailing for water: Why do buildings leak? “(Published 2007 and a supplement in 2014)

Attention is to be given to close off the cavities at building corners or facades that change direction since such cavities must not be open to façade areas that are under differing wind pressures and even negative pressures. The complete pressure equalisation {PE} can be nullified by such cavity extensions of differing pressure conditions.

{Note 2} The cavity between the outer rain screen and the inner air seal can be of a complex form and is to be measured in volume (generally in litres) to be inserted into the formula calculating the drainage areas from the cavity to outside.

{Note 3} With the pressure inside the cavity following that of the exterior fluctuating pressures of the wind, the full wind loading becomes transferred onto the air seal. The air seal is generally made from either gun applied sealants or is made from impervious and waterproof sheeting

of materials and which include their joint sealants. In practise, it is often impossible to achieve full 100% seal to the inside and the research shows that some minor leaks can be accommodated and as shown in the diagram on the previous page. The diagram being the detailed application of the descriptions of words given above. It is of importance that during any testing of an assembly that is designed for PEDJ systems, the pressures are recorded inside the cavity. Refer to the ANZ graph on the next page as to recording the cavity pressures. The air seal is vital since it is generally covered over on the inside of buildings by other interior finishes or linings and cannot be readily maintained or repaired as may be necessary in conditions where earthquakes can occur and when some cracks and thereby air leaks can be developing in the inner seals.

{Note 4} Any collection surfaces of water that has passed the rain screen or is entering via the drainage provisions of the cavity to the outside, must have an adequate fall to the drainage opening and cannot be flat surfaces at any time. (END)

1.6 Added detail explanation on AS/NZS 4284

NOTE

AS/NZS 4284 is a minimum standard and basically outlines the testing procedures and application to see if the specimen passes the test or not. We always add to this extra instrumentation that give us the pressure readings inside the complex cavities of the testing specimen and to assure they do reach what is assumed to be 100% PE. This is not always possible, and we accept figures down to 90% and with explanations. In addition, we always carry out a ‘degradation’ test in which we remove vital outer sealants to demonstrate deteriorations of material that do sometimes need replacement. We also install inner observation ports glazed in acrylic and illuminated inside the cavity by low voltage lights. This is to see the flow of water that has passed the outer rainscreen and which may reach the inner air seal and is then drained out via the drainage slots or openings. We also add deflection instrumentation to see if the cladding is deflecting on the outside (deflection expected to be Zero if the PEDJ is working) and the inner sheeting that forms the inner ‘air seal’ has the expected wind load deflection.

The Canadian diagram on a previous page shows the illustration that represents, in a figure shape, the words that form the “Rules” that go with the PEDJ system. It shows that there are some possible inner air leaks that can be accommodated. Its cross-sectional area is a proportion of the outer drainage and ventilation slot.

This may come handy in earthquake locations where some inner lining, acting as the air seal, may develop cracks (Area “B”). It is always therefore important to keep the drainage slot “A” to an absolute maximum.

The graph below stems from an actual Sirowet test to show that if the correct designs are implemented the PE in the cavity behind the 37 mm polished granite cladding will in fact reach that of the outside dynamic fluctuating wind pressure. Thereby there is no wind load on the granite!

The same results (by installed pressure gauges) were found to exist inside the designed hollow extrusions of the curtain wall.

The actual CSIRO ‘Sirowet’ test on the ANZ 100 Queen Street Melbourne complex curtainwall (also known as 380 Collins Street) with solid granite infills. Showing the zero wind loading on the granite, thanks to correct PEDJ design of the assembly.

We also did a degradation test on applied external sealants and gaskets and it gave the same results. Years later there was a fire on the north side in little Collins Street (11m away) and the chosen Monsanto glazing gasket seals used, were unaffected.

1.7 Dos and don’ts in claddings

Auckland NZ building claddings (Photograph of wet timber) containing a wall wrap, a wall underlay or what we call sarking, is designed to not pass liquids through it. They may be vapour barriers or they may be breathable membranes, they always need the joints to be lapped some 75 mm and the lap be taped over for the life span of that building. Nobody can get access later when the taping has failed and the wind will be blowing right through the lap and carrying the water droplets with it. Above is a typical example on a complex façade when the outer window sills are sculptured and much of the membrane becomes to be on a level surface. With no taping, the water ponds on it and runs right through the lap and wets the timber or corrodes the metal framing below. For results see the picture below, wet timber when we had lifted that membrane off its location. These Auckland NZ illustrations show how their wall underlays in flexible plastic sheeting fails to prevent water passing through it and then wetting the timber frame. It is important that all joints in such materials are taped over with adhesive tapes that will stand there for the life span of the building.

It is what we call “the duck’s back”. In Australia we call it “sarking” and generally use a material that is made from two layers of aluminium foil, that, when taped is a completely watertight layer preventing the timber to decay. Breathable materials provide the passage of high water vapour from the batten cavity into the frame. Most of the decay is initiated by condensation from high humidifies within the building.

2.0 SITE TESTING METHOD AAMA 501.2 (USA)

Alternative site testing of building facades and their claddings, windows, louvred areas etc has been done in other countries that do not use the AS/NZS 4284.

In the early 1960s the CSIRO and testing laboratories in the USA used a setup of propeller driven aircraft engines mounted in front of a test sample and sprayed by sprinklers. The problem with these methods is that there is no real pressure differential caused on the building site of the setup. The USA also uses a hand held method developed by American Manufacturers Association called AAMA 501.2.

The following is an extract of that USA code:-

2.1

AUSTRALIAN ADAPTATION OF A USA CODE ON FIELD CHECK OF WINDOWS & CURTAIN WALLS PART OF A WALL FOR WATER LEAKAGE based on the USA AAMA 501.2

2.1.1 SCOPE AND PURPOSE

This field check is intended to determine the resistance to water penetration of only those joints in the wall which are designed to remain permanently close and watertight a full 100% but shall include joints such as those around doors and openable parts of windows, such as sashes but exclude door sills with an open gaps. Door openings are notorious to leak because of bad design and the lack of the internal air seal around the actual door 100% fully watertight and/or no leakage shall mean that following the test (or tests) there shall have

been no water entries and no dampness showing on the inside of the defence line. Defence line shall mean the assembly of frames and there infills and their joints and sealants and any adjoining masonry construction. All sealants must have had a min. 7 days curing time. The defence line is not the internal finish exposed to the office areas. If needed access openings need to be cut to expose and see the defence line surfaces.

2. 1.2 PREPARATION OF WALL

All window framing and/or wall units shall be installed on the lower two typical floors of the building, or as directed by the Architect/Facade Consultant and at least 20 m lineal length of two-story height shall be fully glazed to provide a complete wall installation including any masonry parts forming part of the facade. All this work shall be done in strict accordance with approved shop drawings and job specifications. The Architect/Facade Consultant will then designate an area of completed wall, two bays in width and two stories in height, to be checked (or as otherwise directed). This area should include all typical horizontal and vertical expansion joints or other mechanical joint conditions plus all gaskets where leakage may occur. The indoor side of the wall in this area shall be unfinished and left open and unobstructed, permitting the full length of all joints to be examined from the indoor side as to water or moisture penetrations as per clause 1 above. If the installation is not of the curtainwall type the Architect / Facade Consultant shall determine the area to be tested.

2.1.3 PROCEDURE

2.1.3.1 Working from the exterior, the wall test section shall be selectively wetted progressing from the lowest horizontal joint, then the intersecting vertical joints, then the next horizontal joint above, etc. The water shall be applied using a Type B-25, # 6.030 brass nozzle with 12mm FPT as manufactured by Monarch Manufacturing Works, Inc., 2501 East Ontario Street, Philadelphia, PA USA (available through Ian Bennie & Associates Melbourne AU) (or other approved make resulting in the same water stream pattern). The nozzle shall be used with a 20mm garden hose (or Australian fire hose reel code equivalent) and shall be provided with a control valve and a pressure gauge between the valve and the nozzle. The water flow to the nozzle shall be adjusted to produce between 200 and 250 kPa water pressure at the nozzle inlet.

2.1.3.2 With the water directed at the joint and perpendicular to the face of the wall, the nozzle shall be moved slowly back and forth above the joint, at a distance of 300mm from it, for a period of five (5) minutes for 1500mm of joint length while an observer on the indoor side of the wail, using a flashlight if necessary, checks for any leakage and notes where they occur.

2.1.3.3 If no leakage occurs during the five-minute test, the next 1500mm of joint shall be wetted for five minutes, and testing continued until the entire test area is covered. This shall include joints between glass and the individual framing member.

2.1.3.4 If water leakage occurs and the source of the leakage cannot be identified, the following sequence shall be followed:

2.1.3.5 Allow the wall to dry and working downward from the top of the area to be checked all joints of every kind within this area shall be completely and tightly covered, on the outdoor side, with a water proof adhesive masking tape.

2.1.3.6 Starting at the bottom of the prepared area, the masking tape shall be removed from the lowest horizontal joint for not more than 1500mm from one end of the joint, including the joint intersection or corner at that end, and this exposed length shall be subjected to the nozzle spray as described in 2.1.3

2.1.3.7 If no leakage occurs during the 5-minute test period, this length of joint shall be considered satisfactory and shall remain uncovered. If leakage has occurred at any point, the joint shall be re-taped at such points to prevent further leakage during the subsequent checking of joints adjacent to or above it. The locations of leaks to be noted on drawings.

2.1.3.8 This process shall then be repeated on all joints and joint intersections within the designated area, using increments of exposed joint length not exceeding 1500mm and always working upward on the wall.

NOTE TO PREVIOUS COMMENTS: - In some cases, due to unforeseen delays or other causes, more than one working day may be required to completely check the designated area, necessitating that some or all the masking tape be left in place overnight. The tape should not remain on finished metal surfaces any longer than necessary, especially where subjected to strong sunlight, as this may make its removal difficult and may also cause staining. It is recommended that in no case should the tape be left in place more than 100 hours.

2.2 REMEDIAL WORK AND RE-CHECKING

2.2.1 Wherever leakage has occurred, joints shall be made watertight in a manner acceptable to the Architect/Facade Consultant. Remedial work involving the use of sealants shall be allowed to set for one week before it is rechecked for leakage.

2.2.2 After all necessary remedial work has been completed, and the required curing time, if any, has elapsed, all repaired joints shall again be checked, following the same procedure as before (Section 3). Should leakage still be found, further remedial measures shall be taken and checking shall be repeated until all joints in the designated area are found to be satisfactory.

3.0. AUSTRALIAN ADOPTATION OF THE AAMA 501.2 ON TALL BUILDINGS

3.1 To create the necessary pressure differences, as mother nature provides us with, you need to install an inside suction box in the areas of testing. This box will be sealed against the inside wall surfaces and is equipped with a fan that produces a negative pressure inside the box. Normally this is minus 500 Pa on static. The length and height are to be the same as the water testing surface area used on the outside. This will also test any connections and part of the adjoining wall surfaces at the same time. It is a “wall with an opening” test. (Often called “Hole in the wall”) Not as the more precise testing under the AS/NZS 4284 (Sirowet rig) principles. We have used this testing on tall buildings in Melbourne up to 100m and on the ‘Sydney Tower’ up to 280m above street level. On buildings with BMU (building maintenance unit) one attaches sprinklers to the moving platform. This can test both single seal as well as PEDJ designed windows.

NOTE: For this specification water leakage is defined as any water or moisture appearing on the inside as set in clause 2.1 of this specification.

Testing facades and roofs on buildings for CONDENSATION is a completely different subject, not covered in this paper.

Bonaldi (Australia) Pty Ltd

Bonaldi (Australia) Pty LtdRESEARCH