IRG Documents Database and Compendium


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An Open Letter to Proponents of CLT/Massive Timber
2016 - IRG/WP 16-40755
We present an Open Letter that discusses the need to address the potential for biodeterioration in CLT/Massive timber structure. We invite members to review and sign the document. We also welcome suggestions for potential recipients....
A Taylor, J Lloyd, T Shelton


The durability of manufactured structural building materials
2016 - IRG/WP 16-40718
The projected market potential for Engineered Wood Products such as CLT (cross laminated timber) is very positive however, potential prolonged rain leakage or moisture exposure during construction and in-service could pose considerable concern for its durability and reputation. This research was conducted to assess the decay resistance of CLT and OSB (oriented strand board) in an accelerated trial...
T Singh, D Page


Corrosion verification experiment of the screw driven into CLT
2017 - IRG/WP 17-40816
Japan has abundant forest resources, but we depend on import for 70 percent of the consumed timber. Japan has the vision which promotes the timber self-sufficiency rate 30% to 50% by 2020. Therefore CLT attracts attention as a new timber material. Japan has a climate with high temperature and humidity, and wooden buildings are often treated with chemicals as a measure against biological deteriorat...
N Wada, H Ishiyama, S Yamamoto


Water absorption characteristics of CLT
2017 - IRG/WP 17-40817
CLT is initialism of Cross Laminated Timber. CLT is generally large-sized panel which can use many woods efficiently, so it is attracted attention recently in Japan. Therefore, many studies about CLT are carried out. However, there are few studies about durability of CLT. Avoiding water infiltration is important for durability of wooden building. CLT has many edge-glued points which has risk of w...
D Yokoi, H Ishiyama, Y Hirano


Development of accelerated decay test for CLT using a fungus grown on agar medium
2019 - IRG/WP 19-20664
CLT is a large-scale wooden board which consists of several layers of sawn lumber stacked in altering directions. Therefore, a lot of large cross sections appear on all narrow faces of CLT. As water penetrates easily into timber from cross section, wooden material whose cross section is exposed to water in in a usage environment is susceptible to deterioration by organisms. Wood deterioration orga...
T Miyauchi, K Kambara, W Ohmura, T Mori, H Matsunaga, N Hattori


Preservative Treatment of CLT: An Example at Shimojishima Airport
2019 - IRG/WP 19-30748
Cross laminated timber (CLT) is a relatively new construction method that allows multi-storey construction using solid wood instead of concrete or steel. It is a method favoured by progressive architects and recognized for its much lower environmental footprint. Wood is an excellent construction material and is a long-term carbon sink that also performs well in the event of earthquakes and fire....
J Lloyd, N Yamashita, A Taylor


Monitoring of the building made of CLT in Ljubljana
2019 - IRG/WP 19-40860
Wood is one of the most important construction materials and its use in building applications has further expanded in recent decades, predominately due to development of the modern composites, like cross-laminated timber. In order to enable even more extensive and reliable use of wood in outdoor applications, factors affecting wood’s service life need to be understood. It is well known that fung...
M Humar, D Krzisnik, B Lesar, N Thaler, B Dujic


The impact of additional interior layers to the moisture dry-out and mould growth risk of CLT walls
2019 - IRG/WP 19-40876
The objective of this study was intended to determine the maximum allowable initial moisture content for CLT walls having both exterior and interior thermal insulation. A laboratory test was conducted, for which four test walls with two different insulation solutions and two different initial moisture contents were built. Based on the test results a simulation model was configured and simulations ...
V Kukk, J Kers, T Kalamees


Fungal damages in Norwegian massive timber elements – causes and measures
2019 - IRG/WP 19-40879
Massive wood elements are relatively new in Norway but the use is growing quickly, primarily the use of cross-laminated timber (CLT). Moisture performance of massive timber elements has been examined by some researchers, but more knowledge is needed. There is uncertainty regarding the need for vapour barriers or retarders in roof assemblies, and for practical reasons buildings are rarely assembled...
M S Austigard, J Mattsson


Adhesion durability of the thinnest CLT in Japan treated by solvent recovery system
2019 - IRG/WP 19-40882
The purpose of this study is to clarify the adhesion durability of the thinnest CLT (36 mm thickness) in Japan impregnated with preservatives (azole neonicotinoid compounds (AZN)) under solvent recovery system so called “dry pressure process” for long-term durability. The adhesion durability tests were conducted in accordance with the Japanese Agricultural Standard (JAS) of Cross-Laminated-Tim...
K Kawakami, W Ohmura


Preliminary investigation for preservation method of CLT using non-pressure treatment
2021 - IRG/WP 21-40919
Cross-laminated Timber (CLT) is increasingly being used in residential and non-residential construction around the world, and some of these areas are at high risk of biodeterioration. Addition to moisture management of construction, preservative treatment of CLT may be needed to prevent decay and termite attack in the area. Pressure treatment being most reliable, is not feasible due to the large d...
T Miyauchi, Y Ohashi, J Miyazaki, R Takanashi, H Shibui, S Isaji, T Shigeyama, Y Sugai, A Yamamoto, T Hramiishi, T Mori, H Matsunaga


Aiming for eco-friendly log production and wooden construction!
2021 - IRG/WP 21-50365
In order to reduce greenhouse gas (GHG) emissions to zero by 2050 in the fields of forest and forest products, it is necessary to promote appropriate management and renewal of planted forests, and development of wooden building materials and the wooden construction of mid-to-high-rise buildings with lower GHG emissions. Unless we also try to reduce the environmental loads other than GHG for such d...
N Hattori


Utilization of Pressure Treated Lumber in Cross Laminated Timber Manufacture and its Impact on Bondline
2022 - IRG/WP 22-40953
Mass timber building construction is increasing dramatically across North America which presents challenges to these structures not seen in Northern Europe. Large parts of the United States harbor termites and existing mass timber building technologies that rely solely on moisture exclusion to increase durability are insufficient in these areas. The successful expansion of mass timber construction...
G Presley, C Wainscott, J Valenti, S Noble


A Comparison of Cross-Laminated Timber (CLT) Floor Panels using Finite Element Analysis and Experimental Fire Testing
2022 - IRG/WP 22-40955
Cross-laminated timber (CLT) is a relatively new timber product and has gained popularity in North America and Europe as a construction material. As a sustainable engineered timber product, CLT offers many advantages over solid wood, concrete, or steel construction. However, the use of timber in medium to high rise buildings is often avoided mainly due to its combustible nature. In this paper, a n...
M Yasir, A Macilwraith, K Ruane


Impacts of elevated moisture levels and subsequent drying on screwed
2023 - IRG/WP 23-40970
Mass timber (glue-laminated timber, cross laminated timber (CLT) and laminated veneer lumber) are increasingly used in mid-to high rise structures in Australia where the climate is mainly sub-tropical with elevated moisture levels and high termite risk. Moisture intrusion poses a major challenge anywhere but becomes more critical under these conditions. Untreated/non-durable materials are consider...
C M T Roder, C D Gerber, J J Morrell


Effect of incised pattern on flexural strength of CLT
2023 - IRG/WP 23-40993
As a study aimed at developing preservation methods suitable for CLT, investigations have been carried out using “deep penetration treatment”. This treatment method was originally developed as a treatment method for sawn lumber and glulam used as sill members. In the treatment, materials are incised using specially designed blades and immediately sprayed with an oil-based wood preservative. Th...
T Mori, R Takanashi, T Miyauchi, Y Ohashi, S Isaji