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In-service performance of wood depends upon the critical in-situ conditions. Case studies.
2008 - IRG/WP 08-20382
Wood is a unique building material, but is by nature designed to deteriorate. A detailed understanding of the factors and interactions involved are important when working with service life prediction of wooden components in buildings. Wood may experience exponential fungal degradation caused by variation in the climatic factors within a small limited area and by minor imperfection in the wooden component. In this paper we put forward a new term: critical in-situ conditions (CIC). This is meant to bring the attention to the importance of looking into details in the construction design, the specific climatic factors and interactions involved. Gaining realistic and useful data for prediction of service life is only possible by controlling and understanding the factors that are target specific for a wooden component or even only a part of it. Performing measurements in a right way and in the proper part of the wooden component are vital for getting useful data for further processing. The objective in this paper is to exemplify the CIC in in-service situations and to describe the factors and interactions that control the service life. Case studies were performed on a building at Bryggen in Bergen, on a hunting cabin on Svalbard, on several wooden windows in the southern part of Norway and on an external wall of a residence house in Ås.
L Ross Gobakken, J Mattsson, G Alfredsen


The critical moisture and temperature conditions for the growth of some mould fungi and the brown rot fungus Coniophora puteana on wood
1988 - IRG/WP 1369
The growth of some mould fungi on pine and spruce sapwood was studied in 40 different constant moisture and temperature conditions. The temperature range was between +10 and +40°C and the relative humidities varied from 76 to 100% relative humidity (RH). The incubation time was 12 weeks. The mixed mould inoculation used included typical fungi growing on wood: Aspergillus versicolor, Cladosporium sphaerospermum, Penicillium sp., Aureobasidium pullullans and other fungi, which were collected from the air in the Forest Products Laboratory. The growth of Coniophora puteana was studied at +20°C and the relative humidity range was between 76 and 100% and the incubation time 60 weeks. The studied moulds grew rapidly in higher humidities (RH > 96%). The lowest humidity for growth was 80%, where the growth was very slow and it could be detected only by microscopy. At higher temperatures the growth was faster and the needed relative humidity was lower than it was in lower temperatures. The brown rot fungus Coniophora puteana grew only at 96-100% RH conditions, where the moisture content of wood was over 25 weight%. The growth was very slow at 96% RH, and after one year incubation the weight losses were quite low. The mycelium strands could mainly be clearly detected, but in some cases no mycelium could be detected on the surface of wood, even if weight losses were measured.
H Viitanen, L Paajanen


Models of the critical time of humidity and temperature conditions for the development of mould fungi in pine and spruce sapwood
1995 - IRG/WP 95-20066
Regression models of the time factor for the growth of mould fungi in pine and spruce sapwood are studied. The first group of models are based on the results of exposures of mould fungi in static humidity and temperature conditions indicating the time for the start of mould growth in wood. The second group of models are based on the exposures of mould fungi in fluctuating or alternating humidity and temperature conditions when limited models are presented. An aspect of surface quality (nutrient rich, nutrient poor) and wood species (pine, spruce) are included in the models. The growth of mould fungi on wooden materials depends mainly on the water activity (the air relative humidity), temperature, exposure time, presence of mould fungi and other organisms and the nutrient content of wood surface. In humidity exposures at RH above 80% (water activity above 0,8) of several weeks - months, the risk for the mould growth in pine and spruce sapwood exists when the temperature is between +5 and +50°C. Between -5 and +5°C, the growth of mould fungi is slow and possible only when the water activity is above 0,9. At water activity above 0.95 (RH 95%), the critical time for mould growth in wood is only some days, when temperature is between +25 and +45°C, and some weeks, when temperature is between +10 and +20°C. Within the same temperature and humidity conditions, the critical time for mould growth on nutrient rich wood is shorter than that of wood with low nutrient content In fluctuating humidity conditions when favourable and unfavourable conditions are alternating, the development of mould fungi is slower and the final rate of mould growth is lower as compared to the constant favourable condition
H Viitanen


Protective Levels of Borates in timber Foundation Piles 5 – 18 Years after In-situ Remedial Treatment in Areas with Wet Clay Ground Conditions. The Jerbor and Eurobor Protocol, Part 1.
2011 - IRG/WP 11-30571
Timber has been used as foundation piles and grillages for decades or even centuries. Since the late 1970s a method for investigate, analyze and treat building timber foundations in soft clay grounds against decay fungus with a biocide have been developed and used by the late professor Allan Jerbo. Settling of buildings in soft clay grounds is continuously monitored and if damages to the building occur as a consequence of differential settling actions must be taken. Settling pattern, ground geotechnical properties and the condition of its timber foundation is evaluated. Settling damage is due to decay of foundation timber have been treated with biocides and special application techniques and results from 5 - 18 years after using these techniques, The Jerbor or Eurobor protocols, show that in-situ treatment with a water solution of borates have been successful. Samples of wood from piles were taken by digging or coring below the building foundations and determination of total boron in wood samples show concentrations in the decay front well above the 1 kg BAE /m3 wood limit for preventing wood degradation by fungi. One example of Jerbor® showed 1.74 kg BAE/m3 wood in average 18 years post treatment simultaneous as the foundation groundwater concentrations was 96 mg BAE/liter in average. To great damage of foundations cannot be repaired and consequently a new steel and concrete foundation have to be made. Costs are often in the 0.5 – 10 million € range for this work why a building benefit from choosing a preservative treatment when this is possible. Approximately 200 foundations have been treated with the Jerbor and Eurobor technique.
M Theorin, K-M Bandh


How to Document the Performance of Super-Critical Treated Wood in above Ground Situations?
2005 - IRG/WP 05-20316
The paper presents practical experiences from the preparation of a new preservative treated wood product for introduction to the market. The product in question is Superwood™, which is treated with organic biocides using CO2 in a supercritical state as a solvent. The question is how to evaluate the performance of a new product such as Superwood™ in order to get an acceptance on the market and fulfil the formal requirements. In the European Union countries, the EN 599-1 is the standard that needs to be complied when approving a new product for the market, but it only focuses on the toxic limit against representative decay fungi according to EN 113. However, decay test, above ground and other forms of field tests are optional, this is not in line with the traditional test philosophy in the Scandinavian countries. The open question is to which extent treatment to the level of the toxic threshold value also ensures a long service life and expected performance of the treated commodity. Superwood™ is evaluated using a strategy, in which basic laboratory tests are done to get the toxic value (according to EN 599-1) and in addition a number of field tests are done including accelerated testing in the tropics. These tests are focussed on the evaluation of the performance criteria such as durability and service life and maintenance requirements. These questions must be answered by the producer without having a full record of performance test for their new products. A short status on the test performed on super-critical treated wood (Superwood™) is presented. Based on a comparison between field test in Scandinavia and in the tropical Malaysia a service life of more than 25 years for a specific supercritical treated product is estimated. It is stated that the existing European standardisation system is insufficient when it comes to service life prediction. A number of important questions need to be addressed by the European standardisation system as soon as possible because the market and the public opinion change quickly due to environmental concern.
N Morsing, A H H Wong, F Imsgard, O Henriksen


Proposed methodology for the assessment of safety indexes
1990 - IRG/WP 3562
Safety Indexes (SI)s are developped on the same concept as Efficacy Indexes (EI)s: EIs are retentions of wood preservatives (percentages of the critical values "efficacy") which are presumed efficient for a given biological class of risk. In the same way, SIs are retentions of wood preservatives (percentages of the critical values "safety") which are taken as acceptable for human health and the general environment. EIs and SIs as well are derived from different types of bioassays and related to objectives of quality which may be either regulatory or harmonized within the programmes of the Standard Committees (CEN TC/38 for example). Critical Values are characteristics of wood preservatives; EIs and SIs are characteristics of treated wood; they vary with the different classes of risks.
G Ozanne


Low temperature drying conditions of Pinus radiata wood for avoiding internal stain
1989 - IRG/WP 3507
It has been observed that, if in little sawmills, timber is dried with a low temperature schedule, it arrives at destination with internal sapstain besides of superficial mould. In this study, the lowest drying temperature at which wood should be exposed for sterilization, which results to be 52°C, is searched. It is not possible to avoid entrainment of pentachlorophenol, even though a waiting period of 72 hours after dipping the wood in a pentachlorophenate/borax solution before drying is considered. The residual content of pentachlorophenol in wood should be at least 400 µg/cm² or the moisture content less than 23% for avoiding the development of mould.
M C Rose


E.R.C. Pole Tester
1982 - IRG/WP 2190
Operating instructions for the ECRC pole-strength tester 120kNm 'PEST'.
G Elcock


Rules and conditions of the Ron Cockcroft Award Scheme RCA
1994 - IRG/WP 94-60025
IRG Secretariat


Wood preservation in France. "Bois plus" chain of quality. Description of the scheme early 1989
1989 - IRG/WP 3519
1989 - description of the French "CTB-BOIS PLUS" homologation scheme...
G Ozanne


Conditions of the Ron Cockcroft Award scheme
1997 - IRG/WP 97-60086
IRG Secretariat


A critical review of the AWPA standard method (M12-72) for laboratory evaluation to determine resistance to subterranean termites
1986 - IRG/WP 1298
The American Wood Preservers' Association standard (M12-72) for evaluation of candidate wood preservatives against subterranean termites is reviewed and suggestions for revision are made. The most serious flaws in the current test procedure involve a failure to recognize inter- and intraspecific variation and a lack of quantification of test results.
J P La Fage, M Jones


Conditions of the Ron Cockcroft Award scheme (RCA)
2003 - IRG/WP 03-60177
IRG Secretariat


Conditions for membership of IRG
1994 - IRG/WP 94-60024
IRG Secretariat


Conditions for membership of IRG
2003 - IRG/WP 03-60176
IRG Secretariat


Effect of protective additives on leachability and efficacy of borate treated wood
2002 - IRG/WP 02-30290
Borate preservatives have been used extensively in many countries as an effective means for protecting wood against fungal and insect attack especially in interior environments. Under exterior conditions, borate compounds have a main disadvantage as they can be leached from treated wood as a result of their water solubility. In this study, we compared the potential of different additives for reducing the leachability of boron preservatives from treated wood. Scots pine sapwood (Pinus sylvestris) and poplar (Populus trichocarpa x deltoides) test samples were vacuum treated with 1 % BAE (Boric Acid Equivalent) disodium octaborate tetrahydrate (DOT) solutions containing various additives e.g. glycerol/glyoxal, polyvinylpyrrolidone (PVPY), a commercial resin compound and a commercial water repellent. The European Standard EN 84 was used as a leaching test for both coated and uncoated specimens. The results of chemical analysis of leachates taken at different periods showed that the use of protective additives reduces the boron leachability. The glycerol/glyoxal additive applied to treated pine sapwood showed the best performance. The percent of boron retained in uncoated pine sapwood was 26% while coated samples still retained 45% after 14 days of intense leaching. Similar tests on poplar revealed 19% and 34% for uncoated and coated samples, respectively.This represents a gain of 20 to 25% compared to pure DOT treated specimens of both wood species. Preliminary biological tests were carried out on malt agar using a miniblock technique for uncoated pine sapwood and beech, with Poria placenta and Coriolus versicolor, respectively. After six weeks of exposure to fungal attack all boron protective systems tested proved their effectiveness, as none of the test samples exhibited a mass loss exceeding 4%. The reference 1% BAE without protective additives showed an average mass loss of 15%. Finally, test data are reported of standard EN 113 testing in view of a further evaluation of the biological efficacy of combined DOT-additive treatments.
A Mohareb, J Van Acker, M Stevens


An attempt to evaluate wood resistance against fungal decay in non-sterile conditions by measuring the variation of resistance to bending test
1988 - IRG/WP 2308
The main object of this work was to determine the variation of strength on large test specimens of wood (800 x 45 x 45 mm³) when exposed to accelerated fungal attacks close to natural conditions, out of test vessels. The modulus of elasticity (MOE) and the modulus of rupture (MOR) have been assessed. Thereby, the natural resistance of the wood species to fungal decay, the efficiency of preservative as well as the treatment applied are discussed. The wood tested is a guianese secondary species (Couma guianensis). The fungi tested are two guianese strains of brown and white rot. The exposure time is 12 weeks. No mould contamination has been recorded by use of a selective fungicide. The results obtained show that it is possible to infest in nonsterile conditions large wood specimens. Furthermore, modulus of rupture appears to be the most reliable criterion. The investigation, that requires limited equipment and staff could be performed in any tropical research station as it has been done at CTFT, French Guiana center.
L N Trong


Observations on the failure of anti-sapstain treated timber under non-drying conditions
1990 - IRG/WP 1437
A range of bacteria and yeasts were isolated from antisapstain treated timber and fresh sawdust. Solution samples containing 100 ppm of TCMTB in a nutrient medium were inoculated with these organisms and incubated at 25°C for 5 days. The levels of TCMTB remaining in solution were determined by HPLC analysis after this time. Results indicated high losses of active ingredient for a range of organisms. These results suggest that active biodetoxification of organic biocides could occur in a short period of time during storage of antisapstain treated timber under favourable conditions. The implications of these results are discussed.
G R Williams


A simple non-destructive means of testing poles in situ
1982 - IRG/WP 2167
Anonymous


Traitement curatif des bois en place. Hygiène et sécurité
1990 - IRG/WP 3585
P Huré


Conditions for membership of IRG
2007 - IRG/WP 07-60246
IRG Secretariat


Conditions and possibility of nanobiocides formulation for wood protection
2008 - IRG/WP 08-30467
During development of nanobiocides for wood protection the need to identify mineral composition of wood in respect of trace elements and nourishing conditions of wood destroying fungi in relation to these elements was discussed.
J Wazny, A Kundzewicz


Conditions for membership of IRGWP
2012 - IRG/WP 12-60338
IRG Secretariat


Conditions for membership of IRGWP
2017 - IRG/WP 17-60411
IRG Secretariat


Performance of surface-treated hardwoods and softwoods out of ground contact
1990 - IRG/WP 3592
A number of fungicides were tested as brush treatments for protection of southern pine, Douglas-fir, maple, and red oak against decay above ground. Cross-brace and L-joint test units were treated just before assembly and exposed from 3-10 years. Untreated Douglas-fir cross-brace units were not decayed at either the Mississippi or Madison, WI, site. Untreated red oak cross-brace units were not decayed at the Madison site. The two hardwood species were more difficult to protect from decay than the softwood species. Decay development in maple cross-brace units was considerably slowed by several of the treatments but none of the treatments provided complete protection from decay during the 9 or 10 years exposure in Mississippi. Most of the treatments did not reduce decay development in red oak cross-brace units. Many treatments protected pine cross-brace units. The L-joints were exposed for only 3-4 years, but appear more difficult to protect from decay than the cross-brace units.
T L Highley


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