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Water Absorption of Various Building Materials and Mold Growth
2008 - IRG/WP 08-10657
Mold growth is a major problem for house owners, as it often occurs on the surface of building materials in damp houses. The principal method to control mold growth on building materials is to prevent water penetration into the materials. A study was recently conducted to determine water absorption rates of different wood species and panel materials used as building materials, when water intrusion occurs. The results showed that solid wood absorbed the least quantity of water among the building materials tested. Upon exposure to water for 7 days, the moisture content (MC) of solid jack pine, black spruce and balsam fir were found to be less than 24% when exposed on one side of the lumber and less than 57% MC when exposed on all sides. Among the three wood panels tested, medium density fiberboard (MDF) and oriented strand board (OSB) had higher water absorption rates, over 70% MC when exposed to water on one side of the panel and over 100% when exposed on all sides. The water absorption rate of plywood lay between that of solid wood and composite panels. Samples of other materials tested, such as gypsum board, fiberglass and ceiling tile, almost reached their saturation point in 1 hour upon water intrusion on all sides of the materials. Most panel samples exposed to water on one side were affected by mold in 7 days; on the other hand, the samples exposed to water on all sides were not affected by mold, because of their very high moisture content.
Dian-Qing Yang


Evaluation of exposure conditions for wooden facades and decking
2009 - IRG/WP 09-20408
During their functional life, building components are exposed to moisture and other environment stress conditions in numerous ways. This is a fact that should be taken into account during manufacture, product development, designing and work execution of building components. For wood material, moisture stress and biological factors like mould and decay fungi are often critical in cladding and decking structure in exterior use conditions. For mould and decay development, different mathematical modelling exists based on laboratory and field studies. These can be used also for evaluating the different material properties for durability and service life of wooden products. In the future, the life time expectations and analyses of different building products will need more data on the durability of products, service life and resistance against mould and decay, not only data on wood material itself. The mould and decay models can be incorporated with climatic and building physic models to evaluate the effect of different exposure conditions on the durability and service life of wooden products.
H Viitanen, T Toratti, R Peuhkuri, T Ojanen, L Makkonen


Drying Rates and Mold Growth on Various Building Materials under Different Environmental Conditions
2010 - IRG/WP 10-20454
Mold growth on building materials is a major problem for homeowners. The most suitable method to control mold growth on building materials is to utilize design features, construction tools and practices that prevent moisture accumulation, and keep the wood as dry as possible. In order to achieve this, engineers and homebuilders have to know the effects of various temperature and moisture conditions on water accumulation and drying speed of various building materials, and the rates at which mold grows in a particular environment. A study was recently conducted at FPInnovations-Forintek Division to determine drying rates and corresponding mold growth on building materials such as oriented strand board (OSB), plywood, fiberboard, gypsum board, fiberglass insulation material, ceiling tile and several Canadian wood species lumber, under different environmental conditions. The results showed that, without ventilation, the sample moisture loss was slow and mold growth was found on test materials that were dried at 72% RH or higher, after 4 days. With ventilation, the drying rates of the various materials were much faster than without ventilation, and were not significantly affected by increasing the temperature from 20°C to 25°C. No mold growth was found on most materials that were dried with ventilation at 64% RH or less.
Dian-Qing Yang


Wood-leather panels – A biological, fire retardant building material
2012 - IRG/WP 12-40615
The poor flame retardant properties of wood-based products are among the severest obstacles, hindering its use in the commercial building sector. Recently, some attempts to improve the fire properties, relying on inflammable salts or reactive halogen compounds, have been presented, although they either cause problems with machining or embody harmful compounds (halogen derivates). In this paper, the fire retardant properties of a novel material, wood-leather panels, are determined by the use of flame tests in a furnace according to ÖNORM EN ISO 1363:2011. The specimens were evaluated according to integrity and surface temperature. For the test specimens, wet white (WW) and wet blue (WB) leather shavings, with varying contents were used. The main finding is that both, panels containing WW and WB leather shavings, show properties superior to current flame-retardant medium density fibre boards, MDF B1,s2-d0. An optimum was found here at a leather content of 50%. In order to describe this behaviour towards fire in further detail, the calorific value of the material as well as the thermal conductivity were determined. As the leather panels produce a foam-like structure during the fire treatment, it is assumed, that this is caused by the exhaust of gases, leading to decreased temperature flow through the specimen, resulting in the observed properties. It can be concluded that the panels show superior fire retardant properties, compared to commonly available flame retardant material. Therefore further research in this field is proposed, with the aim to produce a certified product.
S Wieland, U Stöckl, T Grünewald, S Ostrowski, A Petutschnigg


Method for determining the critical moisture level for mould growth on building materials
2013 - IRG/WP 13-20530
The natural conditions of relative humidity (RH) and temperature (T) in different parts of a building is rarely constant over time. Instead, RH and T often vary cyclically and may pose a risk of mould growth as these conditions are the two key environmental parameters that controls mould growth. Consideration to both humidity and temperature conditions and the susceptibility to mould in a material enables to minimize the risk of future mould damage. The critical moisture level is to be regarded as a temperature dependant material property. As building mate¬rials vary widely in their resistance for mould growth it is not possible to state a critical moisture level of a material without performing tests. The overall aim of this project was to find a way to determine at which level of RH different building materials tend to develop mould growth in order to provide a basic knowledge of the process of designing buildings with low risk of mould growth in accordance with the Swedish building regulations. The results of laboratory tests, together with results from a long field test formed the basis for a new method. This method is designed to evaluate the critical moisture level for mould growth on clean building materials at one specific temperature. In the method, four sets of 7 specimens for each building material are infested with mould spores and then incubated in four levels of relative humidity at 22°C during 12 weeks. During these weeks mould growth analyses are per¬formed regularly. The critical moisture level at the specific temperature is defined by the tested levels of relative humidity. Critical moisture levels at other temperatures may be calculated by using a formula given in the method.
A Ekstrand-Tobin, P Johansson, G Bok


Moisture performance of wood determined in laboratory and field trials
2017 - IRG/WP 17-20621
It is widely accepted that wood moisture content (MC) is the key factor when it comes to durability of wooden structures exposed to weathering. The moisture performance of wood and wood-based products has been recognized as key element in wood durability and wood protection. Actually, it should be considered as major component of the material-intrinsic resistance of wood, but never found its way into a standardized test method (Brischke et al. 2014). Results from field trial at Department of Wood Science and Technology in Ljubljana, floating and submersion tests to determine the residual moisture after cycles of absorption and desorption, the water uptake after 24 h in 100 % relative humidity as well as the capillary uptake in tensiometer test and contact angle measurements are presented in this paper. The influence of accelerated ageing of treated wood on moisture content was also tested in some short-term water uptake tests. As a result, twenty-two wood-based materials were ranked depending on to various conducted tests.
D Kržišnik, N Thaler, B Lesar, M Humar


Preventivephysical barriers against subterranean termites species for building protection: How to implement innovative materials to reach efficacy requirements
2018 - IRG/WP 18-40845
As the European regulation dealing with the use of biocides (BPR) for preventive protection of buildings against subterranean termites is leading to more and more pressure on physico-chemical barriers currently used (PT18), some existing developments are focusing attention on physical biocides-free barriers. The main target is then to avoid the use of active ingredients, to stay out of the BPR scope and cancel the potential risk of health and environmental issues. Different techniques are already on the market displaying good efficacy on special areas where termites can be strongly aggressive, but are often applied and limited to some special implementation areas or potential paths for the termites. This kind of product is not dedicated to cover the whole surface of the building, contrary to biocides treated plastic films that are representing the core-market in France for example. The aim of this paper is to present two different biocides-free materials and/or techniques, which have been developed and tested recently in the company, and gave very promising results for being resistant to termites’ penetration and potentially protect building from subterranean species once implemented before construction. Two different types of preventive physical barriers were proofed at the lab scale according to NF EN 41-550 standard against Reticulitermes and fulfilled the efficacy requirements, with giving also information on the real behaviour of termites when exposed to this kind of material. Improving surface or mechanical properties of some materials can represent an interesting issue for better resistance of pest damages without using any active ingredients. Then, risks of loss of efficacy or potential contact of insecticide generally used in physico-chemical plastic barriers with users or the ground are minimal.
N Delourme-Fonseca, P Poveda, F Simon


Performance of bio-based building materials – durability and moisture dynamics
2020 - IRG/WP 20-20666
When exposed to conditions favourable for decay, bio-based building materials can be susceptible to degradation. Their ability to withstand deterioration over time (performance) depends on the intrinsic or enhanced durability of the material as well as its wetting and drying behaviour. The effect of fungicidal components in wood is known since long. Other material characteristics, such as the material’s moisture dynamics and structure, are crucial as well in prolonging a material’s service life in outdoor exposure conditions. The importance of these other material characteristics should not be underestimated, as there are many opportunities to alter a material’s moisture dynamics and to optimize the structural design of engineered wood products and bio-based insulation products. In order to do so, it is necessary to understand how different material characteristics influence the performance. In this paper, we assess the moisture dynamics of oriented strand board (OSB), porous bituminized wood fibre board (PBF), radiata pine plywood (PL), thermally modified spruce (TMT) and two wood fibre insulation boards (WF-A and WF-B). With the ‘paste test’, we assess whether these materials contain fungicidal components affecting decay. Additionally, we assess how they perform in an adapted mini-block test. We are able to show that fungicidal components are not always of major importance for the durability of a bio-based building material. Some of the assessed materials have a remarkable moisture performance. We need to work towards specific moisture performance criteria and consider including them in performance classification.
L De Ligne, J Caes, S Omar, J Van den Bulcke, J M Baetens, B De Baets, J Van Acker


Evaluation of different wood by-products for sustainable building biomaterial production using fungal mycelium
2022 - IRG/WP 22-50373
As human population increases, the demand for new innovative, sustainable, and low impact construction materials also grows. Mycelium-based composites have shown to be an excellent alternative for traditional products ranging from low-density objects to semi-structural applications. They also present the advantage of using the waste streams from other productive processes as feedstock, enabling the upcycling of materials that can help us transition into a circular economy. In this study three different experiments were carried out: first the selection of the fastest growing fungal strains and the process’ temperature; secondly, three different grain spawn media were evaluated for inoculum production and the last one was a qualitative screening of mycelium growth in different wood by-products. G. lucidum, T. versicolor and P. ostreatus grown at 25 °C were chosen due to their fast-developing rate and mycelium density in comparison to P. eryngii and F. pinicola. For grain spawn production of these strains, a 1:1 mix of wheat and millet was found to be the best option to accelerate the mycelium growth rather than using the grains separately. Different 9x12x4 cm samples were produced using a variety of wood by-product substrates and the shortest production time and more visibly homogeneous material was obtained when growing G. lucidum on beechwood. However, other preliminary test demonstrated the great potential of mixed substrates for production times reduction. The next steps for this research include substrate optimization using mixed wood substrates and further characterization of the bio-composites including thermal conductivity and humidity resistance tests.
C Charpentier-Alfaro, M Poggerini, S Palanti, G Della Rocca, D Pellegrini, A Crisci


Microbiological degradation of wooden piles in building foundations
1988 - IRG/WP 1370
White rot, soft rot and bacterial attack have been detected in softwood piles under buildings. In some cases bacteria were found to be the main degradation organisms in the studied piles. The water content of degraded piles was very high. The compression strength was quite low also in the piles deteriorated by bacteria. The density of wood was very variable, and the degree of degradation could not be evaluated according to density analyses.
L Paajanen, H Viitanen


Sequestration of copper ions by the extracellular mucilaginous material (ECMM) of two wood rotting basidiomycetes
2004 - IRG/WP 04-10533
The radial growth rate of colonies originating from either whole or ECMM-free inocula of Coriolus versicolor was investigated. The presence of ECMM allowed colonies to maintain higher growth rates than those form ECMM-free inocula up to 2 mM CuSO4 in the medium. The ECMM of C. versicolor and G. trabeum was able to reduce the diffusion of copper ions in solution. The ‘raw’ ECMM of both fungi had a greater ability to reduce the diffusion of copper ions than ECMM which had been subject to dialysis to remove soluble, low molecular weight components. The ‘insoluble’ fraction of ECMM for both species was more effective than the ‘soluble’ fraction at reducing the diffusion of copper ions. It is concluded that ECMM confers some protection to hyphae against the toxic effects of copper ions on growth in vivo and that this due to the binding of copper ions to both the polysaccharide and to low molecular weight components of the ECMM
D Vesentini, D J Dickinson, R J Murphy


The restricted distribution of Serpula lacrymans in Australian buildings
1989 - IRG/WP 1382
Temperature data has been gathered over a number of years, not only for flooring regions of various buildings in Melbourne, but also within roof spaces and external to the buildings. Findings are discussed in relation to the distribution of Serpula lacrymans within Australia, its restriction to certain types of building construction and its restriction to flooring regions. The subfloor spaces of badly-ventilated, masonry buildings are highlighted as being better suited than are the subfloor spaces of, for example, Japanese buildings for the activity of this fungus. Hence Serpula lacrymans is very restricted in its distribution in Australia, yet where it is active it does grow rapidly and causes rapid flooring failures.
J D Thornton


An evaluation method for less termite attack execution on thermal insulation for fundation walls
2002 - IRG/WP 02-20245
According to the results by the real scale Japanese building tests, the termite installation was observed at very little spaces between foundation and insulation. The termite penetration spaces between foundation and insulation on foundation systems in Japanese wooden houses were checked by the way of streaming speed of colored water. Because of difficulty for its execution, the parts of outside angles and reentrant angles in continuous foundation were more sensitive for the termite penetration. Special accessories of thermal insulation for these angles can be effective for lesser termite installation.
K Suzuki, Y Tanaka


Problem of the treatment of dried sawn spruce building timbers with water-borne preservatives. Interim reports for discussion at the 4th Annual Meeting in West Berlin on 27 October 1972
1972 - IRG/WP 311
One of the most difficult technical problems facing the preservation industry is how to improve the treatment of refractory species of timber such as spruce. Its resistance to penetration, even under pressure' precludes its use for more hazardous service situations, and even in less severe conditions a higher level of treatment would be desirable. The importance of this subject led us to look once again at possible ways of improving treatment.
W Liese, J W W Morgan, T Hof, R O Ullevålseter


Mould resistance of lignocellulosic material treated with some protective chemicals
1984 - IRG/WP 3294
Effectiveness of preserving lignocellulosic material against moulding by treatement with water solutions of commercial wood preservatives and mixtures of various inorganic salts was investigated and compared with the effectivenes of sodium pentachlorophenoxide and boric acid.
K Lutomski


Contribution to the testing of wood based board material
1982 - IRG/WP 2176
R G Lea


Some thoughts on the future strategy for eradicating Serpula lacrymans from a building
1989 - IRG/WP 1405
We now have a clear view of the mechanism of translocation of nutrients in the mycelium of Serpula lacrymans which is one of the physiological processes underlying the remarkable capacity of this fungus to spread through a building. Here the elements of the mechanism of translocation are dissected out to suggest avenues which might be followed in the search for new ways for eradicating the fungus from buildings.
D H Jennings


The influence of building design on wood decay
2000 - IRG/WP 00-10339
The cheapest and most effective way to prevent wood decay is to KEEP THE WOOD DRY! You and I know that, but we often forget and attempt a preservative solution to a problem better solved with good design and construction. It's also the answer to a frequently missed exam question in my Architecture class. Just as caulking is a poor substitute for proper design, so preservative treatment should be the last resort in an exposure problem, because, what if the treatment fails? Are we in a position to guarantee that every stick we treat will give "life-of-the structure" performance? "All wood rots in time," and "I won't use treated wood because the incisions are ugly," are just two statements I often hear from designers which indicate the uphill battle we have to get designers and builders to use wood properly. Substituting treatment for better design and then providing ineffective treatment have created a lack of trust of treated products among designers and lack of understanding of wood has prevented the creation of good design fixes. "Why should I pay more for treated wood, it doesn't last any longer than the untreated" a Hawaiian contractor told me; he bought thick slabs of Douglas-fir, treated green with CCA, cut them to length in the field, and placed them directly on the ground as a stairway. He was right; Formosan termites gobbled them up in a matter of months. Wrong material, wrong treatment, wrong application! Other case studies will be presented which illustrate situations where use of treated wood was perhaps not the best solution to exposure problems in structures. Prosecuted for murder for allowing the deck on your rental apartment building to decay?--you will see that one, too. (The following text is a transcription of a lecture presented from slides) I am honored to have been asked to address this meeting of the IRG. I was particularly gratified when asked to present a talk on the general subject covered by my title, which I interpreted as dealing with decay situations where pressure treatment may not be the solution of first choice. As most of you know, preservative treatment is not my field; my field is the diagnosis and evaluation of early stages of decay and the improvement of the performance of wood in structures by proper use and design. I get involved, after the fact, in trying to determine why buildings, or parts of them, have failed. But I am not a designer. I am not in a position to show you drawings which tell you how to do it right, although I'm afraid that is what the organizers really wanted from me. Also, no one asks me out to structures that are performing well; I never get to see the good ones! So, I will start by trying to discuss general principles of design which may control performance of wood in structures, but will move very quickly into performance issues which I know more about. The goal of exterior skin design for wooden buildings can be summarized by adapting a borrowed phrase with the anagram of KIDS--keep it dry, stupid! Dry wood can never decay! With the possible exception of particulate wood products, most building materials intended for exterior exposure perform well enough and are assembled with enough redundancy that how they are put together usually is the most important criterion in their performance. The controlling factors usually are minute details. An example is this roof-wall intersection, where the vertical membrane ran underneath the roof membrane, allowing rain water to gather underneath the roof covering. This, probably, was a result of a simple error in scheduling the building trades--the workers installing the wall membranes came on site before the roofers. All exterior design should be focused on shingling of intersecting materials so that water is constantly being shed outward, away from the structure. In the U.S. the major uses of treated products are in utility poles and railroad ties (sleepers to the Commonwealth). These products are purchased by sophisticated buyers who know what they want, what the treating industry can produce (and even sit with them on the committees which establish the treatment standards), and they get what they want--a long-lived product. In my view, the performance problems are primarily in the consumer area where the typical user knows very little about what they want and how to use it, and can't tell the difference between a good product and a bad one. In this area quality control and certification become important, and I'll talk more about that area toward the end. I do, however, have two examples from the consumer/structural arena where pressure-treated wood is being asked to perform unusual duties and is expected to perform well. It's hard to think of a structure being asked to perform under conditions of greater decay hazard than a houseboat. Here the architect used pressure-treated redwood siding to try to weather the extreme conditions of the Sausalito, California waterfront, and then liked the patina of the Chemonite treatment so much that he had the large structural and decorative members painted to match. This is a quite attractive effect which is, to the best of my knowledge, performing well. A "work in progress" is the restoration of a historic structure, the San Francisco Conservatory of Flowers. This structure is scheduled to be demolished, piece by piece, with all of the thousands of pieces of glass retained and the thousands of pieces of old-growth redwood holding them up replaced with exact duplicates made of young-growth redwood through-treated with Chemonite. I have every confidence that this solution, the only reasonable solution we could come up with for a historic structure, will perform superbly, while maintaining the historic fabric and composition of this unique structure. Now on to the area where I have more experience! I don't know about other regions, but wooden deck failures are becoming increasingly important in the Western U.S. Over the last several decades, our drive for quality outdoor living has converted decks from small, temporary attachments to our homes to large, important portions of the structure, expected to have the same performance life as the rest of the structure. Decks are, by definition, outside the protective building envelope and serve in much more decay-conducive environments than most of the rest of the structure, with the possible exception of the roof which is specifically designed to shed the elements. Decks are not. With decks going higher into the air, their failure increasingly involves human injury. The most absurd of such an instance of which I am aware was a deck in San Francisco on a Victorian structure which was being used as rental apartments. This truly was a tragic incident because failure of the deck killed a woman, but it was made more tragic by an overzealous, headline-seeking, District Attorney who decided to prosecute the owner of this building for murder! Now that would certainly do something for quality control in the treating industry if a product failure could lead to criminal prosecution for murder. But this was not treated wood. Should it have been? This is a three-story, Victorian building in a major, high-class, residential area of San Francisco. With this sort of view, you can see why this is a prized place to live, and why decks are popular. This building used to have a third-floor rear deck, attached to the structure at the U-shaped marking beneath the sliding glass door. From talking to the renter of that apartment I learned that he had invited a wedding party to his apartment for the reception. It was a nice day so most everyone was out on the deck. At one point he gathered everyone together for a group picture. Everyone lined up against the outboard handrail, with a spectacular view in the background, for the group picture. The apartment renter, who was near the sliding glass door with the camera, reported hearing a loud snap and, feeling the back of the deck rising, jumped through the open sliding glass door into the apartment. He looked back in horror to see the deck tip forward, hit the second floor deck and bounce, causing it to rotate 90 degrees and flip upside-down on the concrete covered back yard. A number of the guests received serious injuries when they hit the concrete, but one unfortunate woman, most tragically the new bride, ended up underneath the deck and was killed instantly. The headlines the next day touted the negligence of the building owner for allowing his deck to rot, thereby causing this accident. I was called to the site, a seriously unnerving experience, by the attorneys representing the bride's estate in civil court to document the role of decay in causing the failure. But I could not, making me persona non grata because I disagreed with the conventional wisdom carrying forward the case and was never asked to do anything more on it. Let's look at how I came to my unpopular conclusion that decay was not the cause of this accident. This was a 40 or 45-year-old, untreated Douglas-fir deck, not at all an uncommon situation in the San Francisco Bay Area. Certainly, some decay was present, as expected, and there was evidence that decayed members had been replaced from time to time in the life of the structure. There was a good deal of decay in the outboard ends of the stringers, to which the handrail had been attached. If failure of the handrail had been the cause of the injuries, I would have agreed that decay was a culprit. But it was not--the handrail broke on the way down. At the back edge of the deck, where it attached to the wall, the stringers appeared to butt directly to V-rustic siding while sitting on a 2" ledger, with blocking toe-nailed into the stringers and face-nailed into the siding. Portions of the blocking had been replaced with plywood, apparently as a repair for decayed wood. Also visible in this area are relatively new, as yet unpainted, standard joist hangers. These would have been face-nailed into the blocking and the stringers. Now lets focus on the SECOND floor deck, of similar construction. The stringers rest on a ledger, too, but here the joist hangers have so-called "hurricane tabs" which firmly attach the rear of the deck to the ledger. Looking again at the ledger for the third floor deck, we see that it, too, used to have hurricane tabs, but they were removed sometime since the building was given its current coat of paint. Also notice that the failed deck no longer has these tie-downs. This configuration made the third floor deck very vulnerable to pulling away from the wall, which the second floor deck could not do, unless the ledger itself pulled off the building. The third floor deck was supported by a full-width beam placed a considerable distance back from the handrail edge. Again, looking beneath the SECOND floor deck, we see that it, too, had that construction, but that someone had moved the beam outward, toward the handrail, since the last painting, making it more stable to excessive weight applied at the outboard edge. My reconstruction of the failure was that the heavy load of the wedding party having their picture taken against the handrail caused the handrail edge to bend downward, applying an upward force to the back end of the deck, which no longer was tied to the ledger, causing it to pull the face nails and lift off the ledger. Now unstable and rotating about the single support beam, the deck tilted forward, the rear hitting the second floor deck causing it to bounce and flip over. It probably hit at an angle, causing the 90 degree rotation, because the guests were collected at one corner of the handrail for a better background view. The cause of this tragedy was not the fact that 40-year-old untreated decks have decay in them, it was the result of someone, during a repair, substituting standard joist hangers for the original ones with tie-downs at the deck's connection to the building, and the failure to move the support beam further toward the outboard edge of the deck, as had been done for the second floor deck. I don't like personal injury cases to begin with, and I can tell you I hope I never have another failure case where the pieces are adorned with flowers. But the point I want to make in sharing this with you is that the solution to this problem is NOT the use of pressure-treated wood. Parenthetically, it also is not murder! Another deck problem I have encountered involves a design feature called "mill construction." This involves Douglas-fir 2x6 or 2x8s on edge, nail-laminated together. The architects tell me that this system was developed on the then-timber-rich West Coast of the U.S. during WWII, when the Federal Government had sequestered all construction steel. This approach allowed the construction of long-span industrial floors of wood, without the need for steel to stiffen them. There is no reason to use mill construction today; in fact, because it is so wasteful of wood, there is good reason NOT to use it. It is totally inappropriate in residential construction, where such massive strength is unnecessary, and, because of all the capillary spaces between laminates, should never be placed in exterior exposure. In this case, a deck was created by simply making the laminates in this area about six feet longer. Since there was no roof overhang, the only protection for this assembly was a coating of "miracle goop." These all fail eventually leading to a severe decay problem in this mill construction deck. Because of the capillary spaces, the decay progressed back into the building and down into the glulam beam holding up the downhill side of the building. Again, the solution to this problem is NOT pressure-treated wood. This, simply, is a stupid design which should never be used in residential construction, especially in exterior exposure. Now, here's a deck that's a challenge! We've got a lot of steep, very valuable, land overlooking the Pacific Ocean in California, which tempts people to do things like this. Does anyone want to take on responsibility for the treatment of the wood holding up that deck, especially in light of the criminal prosecution in San Francisco? Which brings up the issue of quality control for treated wood entering the consumer market. These data are old, now, but they were produced from a sampling of retail-end lumber which contained a brand by a third-party agency guaranteeing that this lumber met their specifications. Unfortunately, commercial politics destroyed even this agency in the U.S., so there is no organized, even partially reliable, third-party inspection quality assurance available to retail consumers in the U.S. We can not expect builders to rely on treated products if we can't even meet our own minimum standards a majority, let alone approaching 100%, of the time. This is a foundation piling, driven into muck soil to support a structure. The non-green patches are where bark was still present during treating and has sloughed off after drying in place, leaving untreated wood. Even where it is green, the penetration was less than 1/8-inch. The tragedy here is that there are actually over 400 such piles, holding up an 80-unit condominium structure, with no way to replace them. The solution to this problem would have been properly pressure-treated pilings, but, without quality control, that didn't happen. Here is a stack of 6x14, Douglas-fir beams, treated with Chemonite. This shows a pretty good representation of the difficulty of treating sawn Douglas-fir. The problem here is not the quality of treatment (that's actually pretty good for sawn Douglas-fir), the problem is that the designer ordered the beams in the wrong length, requiring that they all be cut to length in the field, exposing the untreated wood you expect at the center. Here, treated wood was the recognized solution, but the end-user messed it up. The developer of this project in Kailua, on Oahu, told me at a seminar in the early eighties that there was no point in paying extra for treated wood because it didn't last any longer than untreated wood. Granted, at that time Hawaii was treating green, sawn Douglas-fir with CCA and calling it "treated" under a "Hawaii use only&quot u32 ?stamp. Still, I jumped at his invitation to see his experience, and this is what I found. The roof of the garages was sodded--a challenge for wood anywhere, but particularly in Formosan termite country. And for the stairways, he was using 3 or 4-inch-thick slabs of sawn Douglas-fir, cut to length in the field, and placed directly on the ground. He was already replacing rotten and termite-eaten treads less than two years into their service life. Maybe you could get away with this with adequately treated wood, but why try? And you certainly won't be successful when the treated wood you're using has penetration like this! Glulams in exterior exposure present a special problem. Most made-up members are too large to treat and, with woods like Douglas-fir where penetration only to the depth of the incisions can be expected, this is clearly not a solution. Treating the laminates also is problematic, not just because of possible effects on gluing, but, in California, the shavings were declared by the State regulators to be a Class I toxic waste. The laminators got rid of their treated wood in a hurry! This project used glulam for nearly everything on the outside of the buildings--through-members protruded beyond the building envelope, blocking and rim-joists were glulam with the sides exposed, they even designed glulam "stubs" to make it look like the beams crossed over the columns. The solution to this problem is NOT pressure treatment. This, again, is simply a matter of stupid design! In fact, because of their innate nature, glulams simply are not members that should be in exterior exposure. Examination of this end, with the various grain orientations of the different laminates, shows that, if this beam were to undergo any significant moisture content cycling, it would develop up-facing checks deep down into the beam, directing water into the center of the member where it becomes trapped and facilitates internal decay. These are solid wood "flying" beams, penetrating the walls on both sides and impossible to flash or caulk successfully because of all of the potential for movement, therefore decaying and leading the decay into each structure. Pressure treatment is not the solution to this problem, this is simply another dumb use of wood. I'm not sure that our fire codes allow this anymore, anyway. I have heard it said by a number of architects that, usually, caulking is simply a dsigner's poor excuse for proper design. Even if it doesn't leak, it creates a lasting, constant maintenance problem for the building maintainer. These examples led to wood decay, but, again, treatment was not the solution. No amount of treatment could overcome the problems caused by this misapplication of grooved plywood siding and scarf-jointed battens. Grooved plywood should never be applied with the grooves horizontal, because it causes up-facing cracks into the center of the panel at the edge of each groove and the groove acts like a gutter directing water to the joint between panels. A properly assembled scarf joint sheds water back to the surface of the two joined pieces, while these reverse scarfs draw water in to the exact location the battens were put on to protect. This is the only case I've ever seen of mushrooms growing directly out of building siding, but treatment would not have helped this either. The siding leaked water into a wall filled with insulation which was, essentially, crushed newspaper, which provided both the moisture and carbon source to support extensive decay. Playground equipment! I've lost track of the number of calls I've gotten from parents asking for a "non-toxic" preservative for the playground equipment their children play on. No matter how you start trying to answer that question, you lose them quickly. This is the equipment my kids played on and I always took the position that I would rather risk their eating a little chemical than running the risk of having one of these huge members decay and come down on their head. Here treatment should be the solution but, because of chemophobic parents, it will only be a workable solution if we can develop deep penetration with that elusive "non-toxic" preservative. Actually, that is what happened with this playground equipment (unfortunately, the "come down on their head" part). The parents club got a number of old 12x12s--former excavation shoring, which had been stored solid-piled on the ground for a number of years. They buried one end in the ground, creating a Stonehenge-like circle of uprights. They fastened eye-bolts to the top of these, now, vertical cantilever members, attached chains which were threaded through old tires, producing a creative, undulating, play surface. Alertness during the construction process would have revealed that these members were badly decayed, as the stack of washers penetrating into the member in an attempt to tighten the nut against a firm surface, showed. Unfortunately, this was another personal injury case. This timber broke at the ground line, hitting a little boy in the head, killing him. This case is just a series of mistakes by well-meaing, but uninformed, people, for which treatment, again, would not have been the solution. But the school's solution--replacing the wooden equipment with steel--also is ill-advised. If my kids were to fall from a piece of playground equipment, I'd much rather they hit their head on wood than a steel 6x6. Wooden roofs should always have a pitch to them, for natural, passive, drainage. All that's needed here is a single pinhole through the roofing material and this roof is a goner. I guess you could get away with this by using adequately treated wood for everything below the water, but why bother? Change the design! Finally, on the West Coast of the U.S., we are building with green lumber which, in many cases, already is infected with decay fungi--the same ones responsible for most above-ground decay. Since most ordinary decay fungi go dormant between wettings, we are building our buildings with the fungi which will decay them already provided. All that's needed is water. The solution to this problem is not treatment, it's kiln-drying. Although I've shown you a number of examples of inadequate wood performance in structures for which I've suggested that preservative treatment would not be the appropriate solution, there are a number of things we should do, I believe, to position preservative treatment in a way to make it available as a solution if other methods prove unsuccessful. Some challenges to preservative research which I recognize would include the following. We need to improve penetration, especially in refractory species like Douglas-fir. Adequate drying prior to treatment, even in large members would help. New approaches, such as vapor metal and cold plasma treatments may hold promise for their ability to increase penetration. We need to find a substitute for visible incisions and, at the same time, achieve deeper incising. I have frequently heard from architects, "I won't use treated wood because those little knife marks are ugly." We need to improve quality control; is the ability to guarantee treatment that meets certain specifications in 100% of pieces treated really not attainable? In our emerging global economy, perhaps quality assurance needs to be taken on by one, or more, international organizations, as in the ISO9002 systems for other commodities. Finally, is it completely impossible to give those parents a "non-toxic" treatment for their playground equipment? The solutions to these issues will require cooperation. Going it alone is an outmoded concept, which, in this era of secrecy and non-cooperation in academia, probably means that the treating industry is going to have to get together and do these things, if they are going to get done. I do, however, have the answer for one of the oldest philosophical questions about being alone. Alan asked me to be a little outrageous and present things that would cause attendees to talk about them in the halls the rest of the week. I think I've done that, Alan. If I went a little overboard, I apologize.
W W Wilcox


Work program of CEN/TC 38 (April 1993). Durability of wood and wood-based products
1993 - IRG/WP 93-20012
R Hüe


Biological performance of gypsum products containing borates
2000 - IRG/WP 00-30237
At suitable retentions borates have biostatic properties enabling them to be used for biodeterioration control in wood. They provide protection against decay fungi, mould, and termites, which are known to also attack gypsum products. Currently, many gypsum products contain added borates, which are used to improve physical and processing characteristics. Work examining the effect of borates at controlling biological attack in gypsum products is presented in this paper. Gypsum or gypsum board with different borate loadings was tested for its performance against dry rot, mould, and subterranean termites in order to see if current commercial levels of borates used in gypsum products would also render them resistant to these common types of biodeterioration. It was confirmed that the presence of borates significantly decreases the amount of biological attack found in gypsum products. From the results obtained it can be concluded that the addition of borates to gypsum products provides more than simple mechanical and processing improvements. For complete biodeterioration control however, especially against mould, higher retentions should be considered. This knowledge could have great significance in the near future, with moves to require termite resistant construction materials (including gypsum board) in some areas and the rising concern of illnesses associated with 'sick building syndrome' caused by in-house mould growth.
J L Fogel, J D Lloyd


Treatment of dried sawn spruce and redwood building timbers with water-borne preservatives under a scheme for the quality control of the preservation and preserved wood in the Netherlands
1978 - IRG/WP 3123
Treatment of dried sawn spruce and redwood Building Timbers with water-borne preservatives under a scheme for the quality control of the preservation and preserved wood in the Netherlands. The aim of this article is to give the reader a modest description of the evaluation of fundamental research in wood preservation into a practical application.
H F M Nijman, N Burgers


Results on termite resistance of building materials against Coptotermes formosanus by choice test
1998 - IRG/WP 98-10275
Various building materials, included wood species, wooden board materials, thermal insulation materials and fire-protection materials, were tested for grading of termite resistance against Coptotermes formosanus. The dimension of most specimens were 2x2x2cm3. Ten repeats were prepared. The specimens were put between Akamatsu sapwood control specimens on a laboratory cultured mound colony of termite, Coptotermes formosanus. After 1 month of attack to termite, the specimens were removed from the mound colony and cleaned up. Then these final mass were weighed. The grading of termite resistance was initially estimated by mass loss of specimens. This grading was corrected by visual observation. Japanese 3 domestic species, cypress pine, Alaska- ceder, kapur and mahogany were indicated rather high termite resistance. In the case of Siberian red pine and Gmelina, the valued of termite resistance were shown variable. Tropical species plywood, inorganic board and radiata pine MDF, were shown rather high termite resistance. Other board materials were shown rather less termite resistance. Most of commercial soft wood plywood and OSB were very sensible against termite. Most common thermal insulation materials in Japan were estimated very sensitive against termite. In the case of fire protection materials, expanded concrete was rather good against termite but plaster board was very sensible against termite.
K Suzuki, K Hagio


Experimental real building evaluation of termite attack - Effect of the space between the mat foundation and the thermal insulation
2000 - IRG/WP 00-10374
For evaluating the termite resistance of the real house foundation, specially in the case of thermal insulation systems for foundation walls, thermal insulation which can be attacked by termite, must be evaluate. Because of the difficulty of the water penetration of thermal insulation, the water barrier systems can be protected against termite attacks, in our opinions. The observation on the process of the penetration by termites and ones of a traditional barrier system against termites were evaluate by the real building scale test method.
K Suzuki, K Hagio, Y Tanaka


A review of environmental emissions from building and construction materials in comparison with preserved wood
2005 - IRG/WP 05-50224-11
A review of the public domain literature concerning emissions to the environment from materials which are used in the construction of buildings (e.g. Concrete, Asphalt, Galvanised Steel), in comparison with preserved wood, and a review of the approaches taken by the construction sector in assessing the risk from environmental emissions, in comparison with the approaches taken by the wood preservation sector.
E F Baines


Japanese Classification of Wooden Building Members for ISO Use Classes according to the Building Code in Japan.
2006 - IRG/WP 06-20337
Because of the international approve of use class system for the biological degradation of wood by ISO/DIS 21887 and ISO/DIS 21892, Japanese committee of ISO/TC165/SC1 asked to the JWPA for classify the wooden commodities by use class of these draft ISO. The JWPA was prepared a draft use class model in Japan. Japanese building code systems are described and Japanese draft use class system is also described.
K Suzuki


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