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7 records – page 1 of 1.

Construction Moisture Management, Cross Laminated Timber

https://research.thinkwood.com/en/permalink/catalogue2685
Year of Publication
2020
Topic
Moisture
Material
CLT (Cross-Laminated Timber)
Author
Wang, Jieying
Organization
FPInnovations
Year of Publication
2020
Format
Book/Guide
Material
CLT (Cross-Laminated Timber)
Topic
Moisture
Keywords
Wetting
Risk Mitigation
Drying
Research Status
Complete
Summary
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.
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Gestion de l'Humidité en Construction, Bois Lamellé-Croisé

https://research.thinkwood.com/en/permalink/catalogue2686
Year of Publication
2020
Topic
Moisture
Material
CLT (Cross-Laminated Timber)
Author
Wang, Jieying
Organization
FPInnovations
Year of Publication
2020
Format
Book/Guide
Material
CLT (Cross-Laminated Timber)
Topic
Moisture
Keywords
Wetting
Risk Mitigation
Drying
Research Status
Complete
Summary
Le bois lamellé-croisé (CLT) est un produit massif de bois d’ingénierie qui est fabriqué à partir de multiples pièces de bois de dimension assemblées en couches orthogonales avec des adhésifs structuraux. Ce produit est conçu pour des conditions de service sèches et est couramment utilisé pour construire des planchers, des toits et des murs. Comme l’humidification prolongée du bois peut causer des taches, de la moisissure, des variations dimensionnelles excessives (parfois suffisantes pour provoquer la défaillance des attaches), et même la pourriture et la perte de résistance, l’humidité est un facteur important dans la construction avec le CLT. Le présent document a pour but de fournir de l’information technique pouvant aider les architectes, les ingénieurs et les constructeurs à évaluer les risques d’humidification du CLT pendant la construction de bâtiments et à prendre les mesures appropriées pour atténuer ces risques.
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Monitoring Moisture Performance of Cross-Laminated Timber Building Elements during Construction

https://research.thinkwood.com/en/permalink/catalogue2102
Year of Publication
2019
Topic
Site Construction Management
Moisture
Material
CLT (Cross-Laminated Timber)
Glulam (Glue-Laminated Timber)
Application
Wood Building Systems

Taller and Larger Wood Buildings: Potential Impacts of Wetting on Performance of Mass Timber Buildings

https://research.thinkwood.com/en/permalink/catalogue372
Year of Publication
2016
Topic
Serviceability
Moisture
Application
Wood Building Systems
Author
Wang, Jieying
Organization
FPInnovations
Year of Publication
2016
Format
Report
Application
Wood Building Systems
Topic
Serviceability
Moisture
Keywords
Wetting
Drying
Wood-Moisture Relationship
Research Status
Complete
Summary
This report summarizes basic wood-moisture relationships, and reviews conditions conducive to adverse consequences of wetting, such as staining, mold growth, decay, strength reduction, and dimensional change and distortion. It also outlines solutions and available resources related to on-site moisture management and design measures. Sorption, including desorption (i.e., loss of moisture) and adsorption (i.e., gain of moisture), is the interaction of wood with the water vapour in the ambient environment. The consequent changes in the amount of bound moisture (or “hygroscopic moisture”) of pre-dried wood affect the physical and mechanical properties. However, the core of a mass timber responds slowly and is well protected from fluctuations in the service environment. Mold growth and fungal staining may occur in a damp environment with a high relative humidity or sources of water. Sorption alone does not increase the moisture content (MC) of pre-dried wood above the fibre saturation point and does not lead to decay. Wood changes its MC more quickly when it absorbs water compared with sorption. This introduces free water (or “capillary water”) and increases the MC above the fiber saturation point. Research has shown that decay does not start below a MC of 26%, when all other conditions are favourable for fungal growth. Decay can cause significant strength reduction, for toughness and impact bending in particular. For a wood member in service, the effect of decay is very complicated and depends on factors, such as the size of a member, loading condition, fungi involved, location and intensity of the attack. Appearance of decay does not reflect true residual stiffness or strength. For wood-based composites severe wetting without decay may affect the structural properties and performance due to damage to the bonding provided by the adhesive inside. There are large variations among wood species, products and assemblies in their tendency to trap moisture and maintain durability. For a given wood species, the longitudinal direction (vs. the transverse directions) and the sapwood (vs. heartwood) absorb water more quickly. Capillaries between unglued joints (e.g., some CLT, glulam), exposed end grains, and interconnected voids inside a product increase the likelihoods of moisture entrapment, slow drying, and consequently decay. Many mass timber products, composites in particular, may be modified to reduce these issues. Measures should also be taken in design, during construction, or building operation to reduce the moisture risk and increase the drying ability. It is also important to facilitate detection of water leaks in a mass timber building and to make it easier to repair and replace members in case damage occurs. Preservative-treated or naturally durable wood should be used for applications that are subjected to high moisture risk. Localized on-site treatment may be appropriate for specific vulnerable locations. Changing environmental conditions may cause issues, such as checking, although it does not compromise the structural integrity in most cases. Measures may be taken to allow the timbers to adjust to the service conditions slowly (e.g., through humidity control), particularly in the first year of service. Overall there is very little information about the potential impacts that various wetting scenarios during construction and in service could realistically have on mass timber products and systems. The wetting and drying behaviour, impacts of wetting and biological attack on the structural capacity, and the behaviour under extreme environmental conditions, such as the very dry service environment that occurs during the winter in a northern continent, should be assessed to improve design of mass timber buildings.
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Wetting and Drying Performance and On-site Moisture Protection of Nail-Laminated Timber Assemblies

https://research.thinkwood.com/en/permalink/catalogue1871
Year of Publication
2016
Topic
Moisture
Material
NLT (Nail-Laminated Timber)
CLT (Cross-Laminated Timber)
Application
Walls
Wood Building Systems
Author
Wang, Jieying
Organization
FPInnovations
Publisher
BC Housing Research Centre
Year of Publication
2016
Format
Report
Material
NLT (Nail-Laminated Timber)
CLT (Cross-Laminated Timber)
Application
Walls
Wood Building Systems
Topic
Moisture
Keywords
Wetting
Drying
Sheathing
Moisture Protection
Space Heating
Research Status
Complete
Summary
In recent years, nail-laminated timber has been increasingly used in wood construction, including both heavy timber non-residential buildings (for floors or roofs) and light wood-frame residential buildings (such as elevator shafts). However, such built-up assemblies, tend to have high wetting and low drying potential and are susceptible to moisture-related issues during the construction. This study evaluates moisture protection by the sheathing or membrane for nail-laminated timber assemblies during on-site construction in British Columbia. Severe wetting will lead to elevated moisture content. Therefore, the best practice when working with nail-laminated timber is to avoid wetting.
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Wetting and Drying Performance of Cross-Laminated Timber Related to On-Site Moisture Protections: Field Measurements and Hygrothermal Simulations

https://research.thinkwood.com/en/permalink/catalogue2711
Year of Publication
2020
Topic
Moisture
Site Construction Management
Material
CLT (Cross-Laminated Timber)
Author
Wang, Lin
Wang, Jieying
Ge, Hua
Organization
Concordia University
FPInnovations
Publisher
EDP Sciences
Year of Publication
2020
Format
Conference Paper
Material
CLT (Cross-Laminated Timber)
Topic
Moisture
Site Construction Management
Keywords
Hygrothermal
Simulation
Hygrothermal Models
On-site Wetting
Conference
Nordic Symposium on Building Physics
Research Status
Complete
Summary
Cross-laminated timber (CLT) panels are increasingly used in mid-rise buildings or even taller structures in North America. However, prolonged exposure to moisture during construction and in service is a durability concern for most wood products including CLT. To investigate practical solutions for reducing on-site wetting of mass timber construction, CLT specimens with a range of moisture protection measures, in six groups were tested in the backyard of FPInnovations’ Vancouver laboratory from Oct. 2017 to Jan. 2018. This study investigates the wetting and drying behaviours of the tested CLT specimens through 2-D hygrothermal simulations. The simulations are performed for base specimens (no protection measures) of group 1 (without joint or plywood spline) and group 2 (with a butt joint and plywood spline). For group 1, three data sources of material properties are used to create the models, and the data that led to the best agreement between simulations and measurement are used for creating the models of group 2. For group 2, two types of hygrothermal models are created with or without considering the differences in water absorption between the transverse and the longitudinal grain orientations. In addition, rain penetration is taken into account for the joint area. It is found that the model with considering the differences between transverse and longitudinal grain orientations shows a better agreement than that without considering such differences.
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Wetting and Drying Performance of Wood-Based Assemblies Related to On-Site Moisture Management

https://research.thinkwood.com/en/permalink/catalogue1782
Year of Publication
2016
Topic
Site Construction Management
Moisture
Material
CLT (Cross-Laminated Timber)
NLT (Nail-Laminated Timber)
Application
Floors
Roofs
Author
Wang, Jieying
Year of Publication
2016
Format
Conference Paper
Material
CLT (Cross-Laminated Timber)
NLT (Nail-Laminated Timber)
Application
Floors
Roofs
Topic
Site Construction Management
Moisture
Keywords
Moisture Content
Wetting
Drying
Construction
Climate
Conference
World Conference on Timber Engineering
Research Status
Complete
Notes
August 22-25, 2016, Vienna, Austria p. 5554-5563
Summary
This document aims to emphasize the importance of an appropriate level of on-site moisture management for wood construction, depending on weather conditions, construction methods, and assemblies used. It covers three different but related research projects. It first describes baseline moisture contents (MCs) measured from...
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7 records – page 1 of 1.