Neither the National Building Code of Canada (NBCC) , nor any provincial code, such as the British Columbia Building Code (BCBC) , currently provide “acceptable solutions” to permit the construction of tall wood buildings, that is buildings of 7 stories and above. British Columbia, however, was the first province in Canada to allow mid-rise (5/6 storey) wood construction and other provinces have since followed. As more mid-rise wood buildings are erected, their benefits are becoming apparent to the industry, and therefore they are gaining popularity and becoming more desirable.
Forest product research has now begun to shift towards more substantial buildings, particularly in terms of height. High-rise buildings, typically taller than 6 storeys, are currently required to achieve 2 h fire resistance ratings (FRR) for floors and other structural elements, and need to be of non-combustible construction, as per the “acceptable solutions” of Division B of the NBCC . In order for a tall wood building to be approved, it must follow an “alternative solution” approach, which requires demonstrating that the design provides an equivalent or greater level of safety as compared to an accepted solution using non-combustible construction. One method to achieve this level of safety is by ‘encapsulating’ the assembly to provide additional protection before wood elements become involved in the fire, as intended by the Code objectives and functional statements (i.e., prolong the time before the wood elements potentially start to char and their structural capacity is affected). It is also necessary to demonstrate that the assembly, in particular the interior finishes, conform to any necessary flame spread requirements.
The Technical Guide for the Design and Construction of Tall Wood Buildings in Canada  recommends designing a tall wood building so that it is code-conforming in all respects, except that it employs mass timber construction. The guide presents various encapsulation methods, from full encapsulation of all wood elements to partial protection of select elements. National Research Council Canada (NRC), FPInnovations, and the Canadian Wood Council (CWC) began specifically investigating encapsulation techniques during their Mid-Rise Wood Buildings Consortium research project, and demonstrated that direct applied gypsum board, cement board and gypsum-concrete can delay the effects of fire on a wood substrate .
There is extensive data on the use of gypsum board as a means of encapsulation for wood-frame assemblies and cold-formed steel assemblies. However, tall wood buildings are more likely to employ mass timber elements due to higher load conditions, requirements for longer fire resistance ratings, as well as other factors. There is little knowledge currently available related to using gypsum board directly applied to mass timber, or in other configurations, for fire protection. Testing performed to date has been limited to direct applied Type X gypsum board using standard screw spacing, and showed promising results [5, 6, 7]. This represents an opportunity for other configurations that might provide enhanced protection of wood elements to be investigated.
Being able to provide equivalent fire performance of assemblies between non-combustible and combustible construction will thus improve the competiveness of tall timber buildings by providing additional options for designers.
The present work aims at evaluating the combustibility characteristics (i.e. reaction to fire) of structural composite lumber (SCL) when tested in compliance with the cone calorimeter standard ISO 5660 [7, 8, 9]. More precisely, this study evaluates the heat release rate, total heat release, mass loss, effective heat of combustion, smoke obscuration as well as the presence of toxic gases when SCL products are tested in conformance with ISO 5660.
Moreover, this study is solely focused on SCL elements that are thick enough to act as semi-infinite solids (thermally thick solids), as opposed to typical thin combustible finish products. Tests data are also compared to those obtained for visually-graded solid wood specimens of the SPF species group.
Laminated products - Fire resistance
Structural Composites - Properties
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To maximize value recovery from post mountain pine beetle - wood (MPB wood) for the manufacture of wood composite products, it is desirable to use completely MPB wood as OSB, MDF or particleboard furnish. The objective of this study in the first fiscal year was to determine and quantify the chemical properties, bondability and wettability of grey stage MPB wood in order to minimize or reduce the impact of beetle-killed wood on composite panel manufacturing. Investigation of the chemical and physical properties of grey stage MPB wood, such as wood pH and buffer capacity, wettability and bondability was conducted. Green lodgepole pine and aspen were used to compare the test results. Various wood furnish derived from MPB wood and green lodgepole pine have been prepared for the manufacturing testing of OSB, MDF and particleboard panels in the next fiscal year. The test results indicated that some basic chemical and physical properties of lodgepole pine, particularly in the sapwood area, had undergone changes associated with MPB infestation.
Based on the test results so far, the following conclusions are made:
1. The pH values of both the MPB heartwood and sapwood were lower and their acid and base buffer capacities were higher than those of the green lodgepole pine. As a result, the curing rate of pH sensitive adhesives such as UF and MUF may be affected.
2. MPB sapwood showed extremely fast and high water absorption but its thickness swell was lower than those of the MPB heartwood, green pine sapwood and heartwood regardless of water temperatures.
3. Thickness swell of the MPB sapwood almost reached to the maximum in the first two hours of water soaking at 20°C.
4. The water absorption of sapwood was higher but the thickness swell was lower than that of heartwood in both MPB wood and green lodgepole pine. The rates of water absorption and thickness swell of these woods were fast in the first several hours and slowed down thereafter.
5. Both the MPB heartwood and the green pine heartwood behaved very similarly in terms of water absorption rate and percentages. It appeared that the beetle infestation did not significantly affect the water absorption property of the MPB heartwood.
6. Edge thickness swell and center thickness swell of the MPB sapwood behaved very similarly in terms of the rates and percentages, which were quite different from those of the other woods and suggest that the blue stained MPB sapwood had probably undergone profound changes.
7. Higher temperatures led to faster and more water absorption. The water temperature affected the MPB sapwood more than the MPB heartwood.
8. Thickness swell reached to the equilibrium faster at higher temperatures.
9. Water pH had little influence on water absorption but affected thickness swell. The thickness swell of both MPB wood and lodgepole pine decreased under both acidic and alkaline conditions.
10. The bonding strength of MPB and green lodgepole pine with liquid PF, powdered PF and liquid UF were generally comparable to that of aspen at high press temperatures. Both the MPB wood and green pine showed lower bonding strength than aspen at low press temperatures. This may have significant implications on the bonding quality of the core layer of panels.
11. At high temperature (200°C), green pine produced substantially higher MDI bonding strength while MPB wood and aspen gave lower and similar bonding strength. This was also the case at low press temperature (140ºC), particularly in longer press time. The MDI bonding strength of MPB wood was close to that of aspen under all these press time and temperature conditions. However, aspen appeared to be less sensitive to low press temperature in terms of bonding with MDI. Therefore, green lodgepole pine may be more suitable as a core furnish material than the MPB wood in the manufacture of OSB, where MDI resin is widely used as a core layer adhesive. Grey stage MPB wood may be more suitable as an OSB face furnish material. This hypothesis will be carefully tested in the 2nd fiscal year of this project.
Insect killed wood - Utilization
Insect-killed wood - Recovery
Pinus contorta Dougl. var. latifolia - North America
FPInnovations a effectué un essai en laboratoire afin d’étudier la teneur en humidité (TH) du bois lamellé-croisé (CLT) découlant du coulage de chapes de béton, et l’efficacité avec laquelle un enduit imperméabilisant et une membrane permettent de de prévenir cette humidification.
Thermal treatments to improve the dimensional stability and durability of wood for exterior applications impart a pleasant dark brown colour but this rapidly fades to gray when exposed to weathering. A coating may solve this problem but adhesion to oil-thermal-treated wood may be an issue. The general objective of this research is to investigate the feasibility of coating oil-thermal-treated post-Mountain Pine Beetle (MPB) lodgepole pine for above-ground residential products such as siding. This is a continuation of previous research in 2006/07 on treating post-MPB lodgepole pine sapwood with oil-thermal treatment, also funded by FII. The current project focuses on surface modification and coating systems evaluation for this treated pine by laboratory tests, and initiating field tests for monitoring long-term coatings performance.
The project was carried out in collaboration with Dr. Paul Cooper of the University of Toronto, Dr. Phil Evans of the University of British Columbia, and Dr. Sam Williams of the Forest Products Laboratory of USDA. Based on the study carried out by FPInnovations–Forintek Division, Sikkens Cetol 123 and SuperNatural showed good adhesion on oil-thermal-treated pine, but the appearance of SuperNatural was preferable for the targeted applications. Hence, SuperNatural was selected for a long-term field test in Vancouver.
Based on the study undertaken by FPL, an aluminum isopropoxide sol-gel precursor was able to improve surface adhesion of the oil-thermal-treated wood for a water-borne finish, but did not improve the adhesion for solvent-borne finishes. The oil-thermal treatment did not appear to appreciably change the hardness or Young’s modulus of the wood based on the nano-indentation measurements. It was also found that the oil-thermal-treated wood could be easily treated with hydroxymethylated resorcinol (HMR), a coupling agent for coating. Its efficacy on coatings performance is being evaluated using an outdoor exposure test.
Based on the University of Toronto’s study, the oil-thermal treatment reduced the wettability of the wood to a number of solvents and had an adverse effect on coating curing and adhesion. Light sanding improved the wetting and resulted in improved adhesion. Among all the finishes evaluated, SuperNatural clear finish formed a hard coat with good adhesion.
The study by the University of British Columbia found that plasma treatment is able to remove oil from the surface of oil-thermal-treated pine, and increased its wettability as well as adhesion to coatings. Scanning electron microscopy, confocal profileometry, and Fourier transform infra-red spectroscopy also indicated that high-energy plasma treatment impacted wood structures, particularly around pits. The consequence of the plasma treatment on coatings performance is being studied with a weathering test.
Overall, the study showed that oil-thermal-treated blue-stained pine can be coated to improve weathering performance for exterior above-ground applications. It confirmed that sanding can improve the coatings performance. The effects of a coupling agent and plasma treatment on coatings performance are to be reported. Thermal modifications may provide a promising way to improve dimensional stability and also mask blue stain for post-MPB lodgepole pine. However, the potential bleeding of oil from wood with initially intense blue stain poses a major challenge for coating application and for developing residential appearance products from the post-MPB lodgepole pine using such an oil-thermal treatment. In that case, alternative thermal treatment processes, particularly using steam as the heating medium, could be considered.
FPInnovations conducted a laboratory test to investigate the potential wetting of cross-laminated timber (CLT) from the pouring of concrete topping, and the effectiveness of a water repellent coating and membrane in preventing such wetting.
Cross-Laminated Timber (CLT) is an engineered mass timber product manufactured by laminating dimension lumber in layers with alternating orientation using structural adhesives. It is intended for use under dry service conditions and is commonly used to build floors, roofs, and walls. Because prolonged wetting of wood may cause staining, mould, excessive dimensional change (sometimes enough to fail connectors), and even result in decay and loss of strength, construction moisture is an important consideration when building with CLT. This document aims to provide technical information to help architects, engineers, and builders assess the potential for wetting of CLT during building construction and identify appropriate actions to mitigate the risk.