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Mass Timber

Mass Timber

Advancements in wood product technology and systems are driving the momentum for innovative buildings in Canada. Products such as cross-laminated timber (CLT), nailed-laminated timber (NLT), glued-laminated timber (GLT), laminated strand lumber (LSL), laminated veneer lumber (LVL) and other large-dimensioned structural composite lumber (SCL) products are part of a bigger classification known as ‘mass timber’.

Although mass timber is an emerging term, traditional post-and-beam (timber frame) construction has been around for centuries. Today, mass timber products can be formed by mechanically fastening and/or bonding with adhesive smaller wood components such as dimension lumber or wood veneers, strands or fibres to form large pre-fabricated wood elements used as beams, columns, arches, walls, floors and roofs. Mass timber products have sufficient volume and cross-sectional dimensions to offer significant benefits in terms of fire, acoustics and structural performance, in addition to providing construction efficiency.

  • Mass Timber
Glulam

Glulam

Glulam (glued-laminated timber) is an engineered structural wood product that consists of multiple individual layers of dimension lumber that are glued together under controlled conditions. All Canadian glulam is manufactured using waterproof adhesives for end jointing and for face bonding and is therefore suitable for both exterior and interior applications. Glulam has high structural capacity and is also an attractive architectural building material.

Glulam is commonly used in post and beam, heavy timber and mass timber structures, as well as wood bridges. Glulam is a structural engineered wood product used for headers, beams, girders, purlins, columns, and heavy trusses. Glulam is also manufactured as curved members, which are typically loaded in combined bending and compression. It can also be shaped to create pitched tapered beams and a variety of load bearing arch and trusses configurations. Glulam is often employed where the structural members are left exposed as an architectural feature.

Glulam block

Available sizes of glulam

Standard sizes have been developed for Canadian glued-laminated timber to allow optimum utilization of lumber which are multiples of the dimensions of the lamstock used for glulam manufacture. Suitable for most applications, standard sizes offer the designer economy and fast delivery. Other non-standard dimensions may be specially ordered at additional cost because of the extra trimming required to produce non-standard sizes. The standard widths and depths of glulam are shown in Table 6.7, below. The depth of glulam is a function of the number of laminations multiplied by the lamination thickness. For economy, 38 mm laminations are used wherever possible, and 19 mm laminations are used where greater degrees of curvature are required.

Standard widths of glulam

Standard finished widths of glulam members and common widths of the laminating stock they are made from are given in Table 4 below. Single widths of stock are used for the complete width dimension for members less than 275 mm (10-7/8″) wide. However, members wider than 175 mm (6-7/8″) may consist of two boards laid side by side. All members wider than 275 mm (10-7/8″) are made from two pieces of lumber placed side by side, with edge joints staggered within the depth of the member. Members wider than 365 mm (14-1/4″) are manufactured in 50 mm (2″) width increments, but will be more expensive than standard widths. Manufacturers should be consulted for advice.

Initial width of glulam stock Finished width of glulam stock
mm. in. mm. in.
89 3-1/2 80 3
140 5-1/2 130 5
184 7-1/4 175 6-7/8
235 (or 89 + 140) 9-1/4 (or 3-1/2 + 5-1/2) 225 (or 215) 8-7/8 (or 8-1/2)
286 (or 89 + 184) 11-1/4 (or 3-1/2 + 7-1/4) 275 (or 265) 10-7/8 (or 10-1/4)
140 + 184 5-1/2 + 7-1/4 315 12-1/4
140 + 235 5-1/2 + 9-1/4 365 14-1/4

Notes:

  • Members wider than 365 mm (14-1/4″) are available in 50 mm (2″) increments but require a special order.
  • Members wider than 175 mm (6-7/8″) may consist of two boards laid side by side with logitudinal joints staggered in adjacent laminations.

Standard depths of glulam

Standard depths for glulam members range from 114 mm (4-1/2″) to 2128 mm (7′) or more in increments of 38 mm (1-1/2″) and l9 mm (3/4″). A member made from 38 mm (1-1/2″) laminations costs significantly less than an equivalent member made from l9 mm (3/4″) laminations. However, the l9 mm (3/4″) laminations allow for a greater amount of curvature than do the 38 mm (1-1/2″) laminations.

Width in. Depth range
mm in.
80 3 114 to 570 4-1/2 to 22-1/2
130 5 152 to 950 6 to 37-1/2
175 6-7/8 190 to 1254 7-1/2 to 49-1/2
215 8-1/2 266 to 1596 10-1/2 to 62-3/4
265 10-1/4 342 to 1976 13-1/2 to 77-3/4
315 12-1/4 380 to 2128 15 to 83-3/4
365 14-1/4 380 to 2128 15 to 83-3/4

Note:
1. Intermediate depths are multiples of the lamination thickness, which is 38 mm (1-1/2″ nom.) except for some curved members that require 19 mm (3/4″ nom.) laminations.

Laminating stock may be end jointed into lengths of up to 40 m (130′) but the practical limitation may depend on transportation clearance restrictions. Therefore, shipping restrictions for a given region should be determined before specifying length, width or shipping height.

Glulam appearance grades

In specifying Canadian glulam products, it is necessary to indicate both the stress grade and the appearance grade required. The appearance of glulam is determined by the degree of finish work done after laminating and not by the appearance of the individual lamination pieces.

Glulam is available in the following appearance grades:

  • Industrial
  • Commercial
  • Quality

The appearance grade defines the amount of patching and finishing work done to the exposed surfaces after laminating (Table 6.8) and has no strength implications. Quality grade provides the greatest degree of finishing and is intended for applications where appearance is important. Industrial grade has the least amount of finishing.

Grade Description
Industrial Grade Intended for use where appearance is not a primary concern such as in industrial buildings; laminating stock may contain natural characteristics allowed for specified stress grade; sides planed to specified dimensions but occasional misses and rough spots allowed; may have broken knots, knot holes, torn grain, checks, wane and other irregularities on surface.
Commercial Grade Intended for painted or flat-gloss varnished surfaces; laminating stock may contain natural characteristics allowed for specified stress grade; sides planed to specified dimensions and all squeezed-out glue removed from surface; knot holes, loose knots, voids, wane or pitch pockets are not replaced by wood inserts or filler on exposed surface.
Quality Grade Intended for high-gloss transparent or polished surfaces, displays natural beauty of wood for best aesthetic appeal; laminating stock may contain natural characteristics allowed for specified stress grade; sides planed to specified dimensions and all squeezed-out glue removed from surface; may have tight knots, firm heart stain and medium sap stain on sides; slightly broken or split knots, slivers, torn grain or checks on surface filled; loose knots, knot holes, wane and pitch pockets removed and replaced with non-shrinking filler or with wood inserts matching wood grain and colour; face laminations free of natural characteristics requiring replacement; faces and sides sanded smooth.

Glulam camber

For long straight members, glulam is usually manufactured with a built in camber to ensure positive drainage by negating deflection. This ability to provide positive camber is a major advantage of glulam. Recommended cambers are shown in Table 5 below.

Table 5: Camber Recommendations for Glulam Roof Beams
Type of Structure Recommendation
Simple Glulam Roof Beams Camber equal to deflection due to dead load plus half of live load or 30 mm per 10 m (1″ per 30′) of span; where ponding may occur, additional camber is usually provided for roof drainage.
Simple Glulam Floor Beams Camber equal to dead load plus one quarter live load deflection or no camber.
Bowstring and Pitched Trusses Only the bottom chord is cambered. For a continuous glulam bottom chord; camber in bottom chord equal to 20 mm per 10 m (3/4″ in 30′) of span.
Flat Roof Trusses (Howe and Pratt Roof Trusses) Camber in top and bottom glulam chords equal to 30 mm per 10 m (1″ in 30′) of span.

Glulam manufacture

The dimension lumber pieces that make up glulam are end jointed and arranged in horizontal layers or laminations. The lumber used for the manufacture of glulam is a special grade (lamstock) that is purchased directly from lumber mills. The lamstock is dried to a maximum moisture content of 15 percent and planed to a closer tolerance than that required for visually graded lumber. Laminating multiple pieces together is an effective way of using high strength dimension lumber of limited length to manufacture glulam members in many cross sectional shapes and lengths. The special grade of lumber used for glulam, lamstock, is received and stored at the laminating plant under controlled conditions. The lamstock must be dried to a moisture content of between 7 and 15% before laminating to maximize adhesion and minimize shrinkage in service. The lumber laminations (lamstock) are visually and mechanically sorted for strength and stiffness into lamstock grades. The assessments of strength and stiffness are used to determine where a given piece will be situated in a beam or column. For example, high strength pieces are placed in the outermost laminations of a beam where the bending stresses are the greatest and for columns and tension members, the stronger laminations are more equally distributed. This blending of strength characteristics is known as grade combination and ensures consistent performance of the finished product. The laminations are glued under pressure using a waterproof adhesive. See Figure 3.7, below, for a schematic representation of glulam manufacture. Glulam beams may also be cambered, which means that they may be produced with a slight upward bow so that the amount of deflection under service loads is reduced. A typical camber is 2 to 4 mm per metre of length. Glulam is manufactured to meet the requirements outlined in CSA O122 Structural GluedLaminated Timber.

Quality Control

Glulam is an engineered wood product requiring exacting quality control at all stages of manufacture. Certified manufacturing plants adhere to quality control standards that govern lumber grading, finger joining, gluing and finishing. Canadian manufacturers of glulam are required to be qualified and certified under CSA O177 Qualification Code for Manufacturers of Structural Glued- Laminated Timber. This standard sets mandatory guidelines for equipment, manufacturing, testing and record keeping procedures. As a mandatory manufacturing procedure, tests must be routinely performed on several critical manufacturing steps, and recording of test results must be done. For example, representative samples are tested for adequacy of glue bond and all end joints are stress tested to ensure that each joint exceeds the design requirements. Each member fabricated has a quality assurance record indicating glue bond test results, lumber grading, end joint test and laminating conditions for each member fabricated, including glue spread rate, assembly time, curing conditions and curing time. In addition, mandatory quality audits are performed by independent certification agencies to ensure that in-plant procedures meet the requirements of the manufacturing standard. A certificate of conformance to manufacturing standards for a given glulam order is available upon request.

Glulam species

Glulam is primarily produced in Canada from two species groups; Douglas fir-Larch and SprucePine. Hem-Fir species are also used occasionally.

Canadian Glulam – Commercial Species
Commercial Species Group Designation Species in Combination Wood Characteristics
Douglas Fir-Larch (D.Fir-L) Douglas fir, western larch Woods similar in strength and weight. High degree of hardness and good resistance to decay. Good nail holding, gluing and painting qualities. Colour ranges from reddish-brown to yellowish-white.
Hem-Fir Western hemlock, amabilis fir, Douglas fir Lightwoods that work easily, take paint well and hold nails well. Good gluing characteristics. Colour range is yellow-brown to white.
Spruce-Pine Spruce (all species except coast sitka spruce), lodgepole pine, jack pine Woods of similar characteristics, they work easily, take paint easily and hold nails well. Generally white to pale yellow in colour.

Glulam strength grades

In specifying Canadian glulam products, it is necessary to indicate both the stress grade and the appearance grade required. The specification of the appropriate stress grade depends on whether the intended end use of a member is for a beam, a column, or a tension member as shown in Table 2.

Table 2: Canadian Glulam – Stress Grades
Stress Grade Species Description
Bending Grades 20f-E and 20f-EX D.Fir-L or Spruce Pine Used for members stressed principally in bending (beams) or in combined bending and axial load.
24f-E and 24f-EX D.Fir-L or Hem-Fir Specify EX when members are subject to positive and negative moments or when members are subject to combined bending and axial load such as arches and truss top chords.
Compression Grades 16c-E 12c-E D.Fir-L Spruce Pine Used for members stressed principally in axial compression, such as columns.
Tension Grades 18t-E 14t-E D.Fir-L Spruce Pine Used for members stressed principally in axial tension, such as bottom chords of trusses.

For the bending grades of 20f-E, 20f-EX, 24f-E and 24f-EX, the numbers 20 and 24 indicate allowable bending stress for bending in Imperial units (2000 and 2400 pounds per square inch). Similarly the descriptions for compression grades,16c-E and 12c-E, and tension grades,18t-E and 14t-E indicate the allowable compression and tension stresses. The “E” indicates that most laminations must be tested for stiffness by machine. The lower case letters indicate the use of the grade as follows: “f” is for flexural (bending) members, “c” is for compression members, and “t” is for tension members. Stress grades with EX designation (20f-EX and 24f-EX) are specifically designed for cases where bending members are subjected to stress reversals. In these members the lamination requirements in the tension side are the mirror image of those in the compression side. Unlike visually graded sawn timbers where there is a correlation between appearance and strength, there is no relationship between the stress grades and the appearance grades of glulam since the exposed surface can be altered or repaired without affecting the strength characteristics.

Moisture Control of Glulam

The checking of wood is due to differential shrinkage of the wood fibres in the inner and outer portions of a wood member. Glulam is manufactured from lamstock having a moisture content of 7 to 15 percent. Because this range approximates the moisture conditions for most end uses, checking is minimal in glulam members. Proper transit, storage and construction methods help to avoid rapid changes in the moisture content of laminated members. Severe moisture content changes can result from the sudden application of heat to buildings under construction in cold weather, or from exposure of unprotected members to alternate wet and dry conditions as might occur during transit and storage. Canadian glulam routinely receives a coat of protective sealer before shipping and is wrapped for protection during shipping and erection. The wrapping should be left in place as long as possible and ideally until permanent protection from the weather is in place. During on-site storage, glulam should be stored off the ground with spacer blocks placed between members. If construction delays occur, the wrapping should be cut on the underside to prevent the accumulation of condensation.

Treatment and sealant for glulam

Preservative treatment is not often required but should be specified for any application where ground contact is likely. Advice on suitable preservative treatment should be sought from the manufacturer. Untreated glulam can be used in humid environments such as swimming pools, curling rinks or in industrial buildings which use water in their manufacturing process. Where the ends of glulam members will be subject to wetting, protective overhangs or flashings should be provided. In applications where direct water contact is not a factor, a factory applied sealer will prevent large swings in moisture content. The alkyd sealer applied to glulam members in the factory provides adequate protection for most high-humidity applications. Since wood is corrosion-resistant, glulam is used in many corrosive environments such as salt storage domes and potash warehousing.

Common glulam shapes

For more information on individual glulam manufacturers in Canada, refer to the following links:

Western Archrib
Mercer Mass Timber
Nordic Structures
Goodfellow
Kalesnikoff Mass timber
Element5

Solid-Sawn Heavy Timber

Solid-sawn heavy timber members are predominantly employed as the main structural elements in post and beam construction. The term ‘heavy timber’ is used to describe solid sawn lumber which is 140 mm (5-1/2 in) or more in its smallest cross-sectional dimension. Large dimension timbers offer increased fire resistance compared to dimensional lumber and can be used to meet the heavy timber construction requirements outlined in the Part 3 of the National Building Code of Canada.

Sawn timbers are produced in accordance with CSA O141 Canadian Standard Lumber and graded in accordance with the NLGA Standard Grading Rules for Canadian Lumber.

There are two categories of timbers; rectangular “Beams and Stringers” and square “Posts and Timbers”. Beams and Stringers, whose larger dimension exceeds its smaller dimension by more than 51 mm (2 in), are typically used as bending members, whereas, Posts and Timbers, whose larger dimension exceeds its smaller dimension by 51 mm (2 in) or less, are typically used as columns.

Sawn timbers range in size from 140 to 394 mm (5-1/2 to 15-1/2 in). The most common sizes range from 140 x 140 mm (5-1/2 x 5-1/2 in) to 292 x 495 mm (11-1/2 x 19-1/2 in) in lengths of 5 to 9 m (16 to 30 ft). Sizes up to 394 x 394 mm (15-1/2 x 15-1/2 in) are generally available from Western Canada in the Douglas Fir-Larch and Hem-Fir species combinations. Timbers from the Spruce-Pine-Fir (S-P-F) and Northern species combinations are only available in smaller sizes. Timbers may be obtained in lengths up to 9.1 m (30 ft), but the availability of large size and long length timbers should always be confirmed with suppliers prior to specifying. A table of available timber sizes is shown below.

Both categories of timbers, Beams and Stringers, and Posts and Timbers, contain three stress grades: Select Structural, No.1, and No.2, and two non-stress grades (Standard and Utility). The stress grades are assigned design values for use as structural members. Non-stress grades have not been assigned design values.

No.1 or No.2 are the most common grades specified for structural purposes. No.1 may contain varying amounts of Select Structural, depending on the manufacturer. Unlike Canadian dimension lumber, there is a difference between design values for No.1 and No.2 grades for timbers. Select Structural is specified when the highest quality appearance and strength are desired.

The Standard and Utility grades have not been assigned design values. Timbers of these grades are permitted for use in specific applications of building codes where high strength is not important, such as blocking or short bracing.

Cross cutting can affect the grade of timber in the Beams and Stringers category because the allowable size of knot varies along the length of the piece (a larger knot is allowed near the ends than in the middle). Timbers must be regraded if cross cut.

Timbers are generally not grade marked (grade stamped) and a mill certificate can be obtained to certify the grade.

The large size of timbers makes kiln drying impractical due to the drying stresses which would result from differential moisture contents between the interior and exterior of the timber. For this reason, timbers are usually dressed green (moisture content above 19 percent), and the moisture content of timber upon delivery will depend on the amount of air drying which has taken place.

Like dimension lumber, timber begins to shrink when its moisture content falls below about 28 percent. Timbers exposed to the outdoors usually shrink from 1.8 to 2.6 percent in width and thickness, depending on the species. Timbers used indoors, where the air is often drier, experience greater shrinkage, in the range of 2.4 to 3.0 percent in width and thickness. Length change in either case is negligible. Allowances for anticipated shrinkage should be made in the design and construction. Shrinkage should also be considered when designing connections.

Minor checks on the surface of a timber are common in both wet and dry service conditions. Consideration has been made for these surface checks in the establishment of specified design strengths. Checks in columns are not of structural importance unless the check develops into a through split that will divide the column.

 

For further information, refer to the following resources:

Timber Framers Guild

International Log Builders’ Association

BC Log & Timber Building Industry Association

 

solid-sawn mass timber size chart

Plank Decking

Plank decking may be used to span farther and carry greater loads than panel products such as plywood and oriented strand board (OSB). Plank decking is often used where the appearance of the decking is desired as an architectural feature or where the fire performance must meet the heavy timber construction requirements outlined in Part 3 of the National Building Code of Canada. Plank decking is usually used in mass timber or post and beam structures and is laid with the flat or wide face over supports to provide a structural deck for floors and roofs.

Plank decking can be used in either wet or dry service conditions and can be treated with preservatives, dependent on the wood species. Nails and deck spikes are used to fasten adjacent pieces of plank decking to one another and are also used to fasten the deck to its supports.

Decking is generally available in the following species:

  • Douglas fir (D.Fir-L species combination)
  • Pacific coast hemlock (Hem-Fir species combination)
  • Various species of spruce, pine and fir (S-P-F species combination)
  • Western red cedar (Northern species combination)

In order to product plank decking, sawn lumber is milled into a tongue and groove profile with special surface machining, such as a V-joint. Plank decking is normally produced in three thicknesses: 38 mm (1-1/2 in), 64 mm (2-1/2 in) and 89 mm (3-1/2 in). The 38 mm (1-1/2 in) decking has a single tongue and groove while the thicker sizes have a double tongue and groove. Thicknesses greater than 38 mm (1-1/2 in) also have 6 mm (1/4 in) diameter holes at 760 mm (2.5 ft) spacing so that each piece may be nailed to the adjacent one with deck spikes. The standard sizes and profiles are shown below.

Plank decking is most readily available in random lengths of 1.8 to 6.1 m (6 to 20 ft). Decking can be ordered in specific lengths, but limited availability and extra costs should be expected. A typical specification for random lengths could require that at least 90 percent of the plank decking be 3.0 m (10 ft) and longer, and at least 40 percent be 4.9 m (16 ft) and longer.

Plank decking is available in two grades:

  • Select grade (Sel)
  • Commercial grade (Com)

Select grade has a higher quality appearance and is also stronger and stiffer than commercial grade.

Plank decking is required to be manufactured in accordance with CSA O141 and graded under the NLGA Standard Grading Rules for Canadian Lumber. Since plank decking is not grade stamped like dimensional lumber, verification of the grade should be obtained in writing from the supplier or a qualified grading agency should be retained to check the supplied material.

To minimize shrinkage and warping, plank decking consists of sawn lumber members that are dried to a moisture content of 19 percent or less at the time of surfacing (S-Dry). The use of green decking can result in the loosening of the tongue and groove joint over time and a reduction in structural and serviceability performance.

Individual planks can span simply between supports, but are generally random lengths spanning several supports for economy and to take advantage of increased stiffness. There are three methods of installing plank decking: controlled random, simple span and two span continuous. A general design rule for controlled random plank decking is that spans should not be more than 600 mm (2 ft) longer than the length which 40 percent of the decking shipment exceeds. Both the latter methods of installation require planks of predetermined length and a consequently there could be an associated cost premium.

 

Plank Decking

 

Profiles and Sizes of Plank Decking

Plank Decking

Tall Wood Buildings

With advanced construction technologies and modern mass timber products such as glued-laminated timber, cross-laminated timber and structural composite lumber, building tall with wood is not only achievable but already underway – with completed contemporary buildings in Australia, Austria, Switzerland, Germany, Norway and the United Kingdom at 9 storeys and taller. Increasingly recognized by the construction sector as an important, new, and safe construction choice, the reduced carbon footprint and embodied / operational energy performance of these buildings is appealing to communities that are committed to sustainable development and climate change mitigation.

Tall wood buildings, built with renewable wood products from sustainably managed forests, have the potential to revolutionize a construction industry increasingly focused on being part of the solution when it comes to urban intensification and environmental impact reduction. The Canadian wood product industry is committed to building on its natural advantage, through the development and demonstration of continuously improving wood-based building products and building systems.

A tall wood building is a building over six-storeys in height (top floor is higher than 18 m above grade) that utilizes mass timber elements as a functional component of its structural support system. With advanced construction technologies and modern mass timber products such as glued-laminated timber (glulam), cross-laminated timber (CLT) and structural composite lumber (SCL), building tall with wood is not only achievable but already underway – with completed contemporary buildings in Canada, US, Australia, Austria, Switzerland, Germany, Norway, Sweden, Italy and the United Kingdom at seven-storeys and taller.

Tall wood buildings incorporate modern fire suppression and protection systems, along with new technologies for acoustic and thermal performance. Tall wood buildings are commonly employed for residential, commercial and institutional occupancies.

Mass timber offers advantages such as improved dimensional stability and better fire performance during construction and occupancy. These new products are also prefabricated and offer tremendous opportunities to improve the speed of erection and quality of construction.

Some significant advantages of tall wood buildings include:

  • the ability to build higher in areas of poor soils, as the super structure and foundations are lighter compared to other building materials;
  • quieter to build on site, which means neighbours are less likely to complain and workers are not exposed to high levels of noise;
  • worker safety during construction can be improved with the ability to work off large mass timber floor plates;
  • prefabricated components manufactured to tight tolerances can reduce the duration of construction;
  • tight tolerances in the building structure and building envelope coupled with energy modelling can produce buildings with high operational energy performance, increased air tightness, better indoor air quality and improved human comfort

Design criteria for tall wood buildings that should be considered include: an integrated design, approvals and construction strategy, differential shrinkage between dissimilar materials, acoustic performance, behaviour under wind and seismic loads, fire performance (e.g., encapsulating the mass timber elements using gypsum), durability, and construction sequencing to reduce the exposure of wood to the elements.

It is important to ensure early involvement by a mass timber supplier that can provide design assistance services that can further reduce manufacturing costs through the optimization of the entire building system and not just individual elements. Even small contributions, in connection designs for example, can make a difference to the speed of erection and overall cost. In addition, mechanical and electrical trades should be invited in a design-assist role at the outset of the project. This allows for a more complete virtual model, additional prefabrication opportunities and quicker installation.

Recent case studies of modern tall wood buildings in Canada and around the world showcase the fact that wood is a viable solution for attaining a safe, cost-effective and high-performance tall building.

For more information, refer to the following case studies and references:

Brock Commons Tall Wood House (Canadian Wood Council)

Origine Point-aux-Lievres Ecocondos,Quebec City (Cecobois)

Wood Innovation and Design Centre (Canadian Wood Council)

Technical Guide for the Design and Construction of Tall Wood Buildings in Canada (FPInnovations)

Ontario’s Tall Wood Building Reference (Ministry of Natural Resources and Forestry & Ministry of Municipal Affairs)

Summary Report: Survey of International Tall Wood Buildings (Forestry Innovation Investment & Binational Softwood Lumber Council)

www.thinkwood.com/building-better/taller-buildings

Tall Wood Buildings – Research

Tests

Current research includes the World’s largest mass timber fire test – click here for updates on the test results currently being conducted https://firetests.cwc.ca/

Studies

Reports

Fire Research

Acoustics Research and Guides

Tall Wood Building Demonstration Initiative Test Reports
(funding provided by Natural Resources Canada)

Visit Think Wood’s Research Library for additional resources

Mid-Rise Buildings – Research

Studies

General

Structural & Seismic

Vertical Movement in Wood Platform Frame Structures (CWC Fact Sheets)

Design of multi-storey wood-based shearwalls: Linear dynamic analysis & mechanics based approach

Fire

Testing

Fire Research

Research for Wood and Wood-Hybrid Mid-Rise Buildings Project
National Research Council Canada (2011-2015)

Other Reports

Acoustics Research

Research for Wood and Wood-Hybrid Mid-Rise Buildings Project
National Research Council Canada (2011-2015)

Other Reports & Guides

Building Envelope Research

Research for Wood and Wood-Hybrid Mid-Rise Buildings Project
National Research Council Canada (2011-2015)

Visit Think Wood’s Research Library for additional resources

banner for research.thinkwood.com

Climate Change

Concerns about climate change are encouraging decarbonization of the building sector, including the use of construction materials responsible for fewer greenhouse gas (GHG) emissions and improvements in operational performance over the life cycle of buildings. Accounting for over 10 percent of total GHG emissions in Canada, the building sector plays an important role in climate change mitigation and adaptation. Decreasing the climate change impacts of buildings offers high environmental returns for relatively low economic investment.

The Government of Canada, as a signatory to the Paris Agreement, has committed to reducing Canada’s GHG emissions by 30 percent below 2005 levels by 2030. In addition, the Pan-Canadian Framework on Clean Growth and Climate Change acknowledges that forest and wood products have the ability to contribute to the national emissions reductions strategy through:

  • enhancing carbon storage in forests;
  • increasing the use of wood for construction;
  • generating fuel from bioenergy and bioproducts; and
  • advancing innovation in bio-based product development and forest management practices.

The importance of the forestry and wood products sector as a critical component toward mitigating the effects of climate change is also echoed by the Intergovernmental Panel on Climate Change (IPCC); stating that a sustainable forest management strategy aimed at maintaining or increasing forest carbon stocks while producing timber, fibre, or energy, generates the largest sustained benefit to mitigate climate change. In addition, the IPCC proclaims that “mitigating options by the forest sector include extending carbon retention in HWP [harvested wood products], product substitution, and producing biomass for bioenergy.”

The Canadian forest industry is pledging to remove 30 megatons of carbon dioxide (CO2) a year by 2030, equivalent to 13 percent of Canada’s national commitments under the Paris Agreement. Several mechanisms will be employed to meet this challenge, including:

  • product displacement, using bio-based products in place of fossil fuel-derived products and energy sources;
  • forest management practices, including increased utilization, improved residue use and land use planning, and better growth and yields;
  • accounting for long-lived bio-based product carbon pools; and
  • higher efficiencies in wood product manufacturing processes

Canada is home to 9 percent of the world’s forests, which have the ability to act as enormous carbon sinks by absorbing and storing carbon. Annually, Canada harvests less than one-half of one percent of its forest land, allowing for the forest cover in Canada to remain constant for last century. Sustainable forest management and legal requirements for reforestation continue to maintain this vast carbon reservoir. A forest is a natural system that is considered carbon neutral as long as it is managed sustainably, which means it must be reforested after harvest and not converted to other land uses. Canada has some of the strictest forest management regulations in the world, requiring successful regeneration after public forests are harvested. When managed with stewardship, forests are a renewable resource that will be available for future generations.

Canada is also a world leader in voluntary third-party forest certification, adding further assurance of sustainable forest management. Sustainable forest management programs and certification schemes strive to preserve the quantity and quality of forests for future generations, respect the biological diversity of the forests and the ecology of the species living within it, and respect the communities affected by the forests. Canadian companies have achieved third-party certification on over 150 million hectares (370 million acres) of forests, the largest area of certified forests in the world.

The forest represents one carbon pool, storing biogenic carbon in soils and trees. The carbon remains stored until the trees die and decay or burn. When a tree is cut, 40 to 60 percent of the biogenic carbon remains in the forest; the rest is removed as logs and much of it is transferred to the wood products carbon pool within the built environment. Wood products continue to store this biogenic carbon, often for decades in the case of wood buildings, delaying or preventing the release of CO2 emissions.

Wood products and building systems have ability to store large amounts of carbon; 1 m3 of S-P-F lumber stores approximately 1 tonne of CO2 equivalent. The amount of carbon stored within a wood product is directly proportional the density of the wood. The average single-family home in Canada stores almost 30 tonnes of CO2 equivalent within the wood products used for its construction. Most bio-based construction products actually store more carbon in the wood fibre than is released during the harvesting, manufacturing and transportation stages of their life cycle.

In general, bio-based products like wood that are naturally grown with help from the sun have lower embodied emissions. The embodied emissions arise through the production processes of building materials, starting with resource extraction or harvesting through manufacturing, transportation, construction, and end-of-life. Bioenergy produced from bio-based residuals, such as tree bark and sawdust, is primarily used to generate energy for the manufacture of wood products in North America. Wood construction products have low embodied GHG emissions because they are grown using renewable solar energy, use little fossil fuel energy during manufacturing, and have many end-of-life options (reuse, recycle, energy recovery).

Wood products have the ability to substitute for other more carbon-intensive building materials and energy sources. GHG emissions are thereby avoided by using wood products instead of other more GHG-intensive building products. Displacement factors (kg CO2 avoided per kg wood used) have been estimated to calculate the amount of carbon avoided through the use of wood products in building construction.

 

For further information, refer to the following resources:

Addressing Climate Change in the Building Sector – Carbon Emissions Reductions (Canadian Wood Council)

Resilient and Adaptive Design Using Wood (Canadian Wood Council)

CWC Carbon Calculator

Canada’s Forest Products Industry “30 by 30” Climate Change Challenge (Forest Products Association of Canada)

www.naturallywood.com

www.thinkwood.com

Building with wood = Proactive climate protection (Binational Softwood Lumber Council and State University of New York)

Natural Resources Canada

Pan-Canadian Framework on Clean Growth and Climate Change (Government of Canada)

Intergovernmental Panel on Climate Change

Codes & Standards

BUILDING CODES & STANDARDS (THE REGULATORY SYSTEM)

The construction industry is regulated through building codes which are informed by:

  • Design standards that provide information on “how to” build with wood,
  • Product standards that define the characteristics of the wood products that can be used in design standards, and
  • Test standards that set out the methodology for establishing a wood product’s characteristics

CWC is active in a technical capacity in all areas of the Regulatory System. This includes:

BUILDING CODES – CWC participates extensively in the development process of the Building Codes in Canada. CWC is a member of both National and Provincial Building Code Committees. These Committees are balanced and representation is limited to about 25 members on each Committee. Competing interests (i.e. steel and concrete) sit on the same Committees. This is an arena where CWC can win or lose ground for members’ products.

DESIGN STANDARDS – Each producer of structural materials develops engineering design standards that provide information on how to use their products in buildings. CWC holds the Secretariat for Canada’s wood design standard (CSA O86 “Engineering Design in Wood”), providing both technical expertise and administrative support for its development. CWC is also a member of the American Wood Council (AWC) committee that is responsible for the U.S. National Design Specification for wood design.

PRODUCT STANDARDS – CWC is involved in the development of Canadian, U.S. and international standards for its wood building product producers.

TEST STANDARDS – CWC is involved in developing Canadian, U.S. and international test standards in areas that affect wood products, such as fire performance.

Detailed building codes & standards pages:

Acoustics

Wood is composed of many small cellular tubes that are predominantly filled with air. The natural composition of the material allows for wood to act as an effective acoustical insulator and provides it with the ability to dampen vibrations. These sound-dampening characteristics allow for wood construction elements to be specified where sound insulation or amplification is required, such as libraries and auditoriums. Another important acoustical property of wood is its ability to limit impact noise transmission, an issue commonly associated with harder, more dense materials and construction systems.

The use of topping or a built-up floating floor system overlaid on light wood frame or mass timber structural elements is a common approach to address acoustic separation between floors of a building. Depending on the type of materials in the built-up floor system, the topping can be applied directly to the wood structural members or over top of a moisture barrier or resilient layer. The use of gypsum board, absorptive (batt/loose-fill) insulation and resilient channels are also critical components of a wood-frame wall or floor assembly that also contribute to the acoustical performance of the overall assembly.

Acoustic design considers a number of factors, including building location and orientation, as well as the insulation or separation of noise-producing functions and building elements. Sound Transmission Class (STC), Apparent Sound Transmission Class (ASTC) and Impact Insulation Class (IIC) ratings are used to establish the level of acoustic performance of building products and systems. The different ratings can be determined on the basis of standardized laboratory testing or, in the case of ASTC ratings, calculated using methodologies described in the NBC.

Currently, the National Building Code of Canada (NBC) only regulates the acoustical design of interior wall and floor assemblies that separate dwelling units (e.g. apartments, houses, hotel rooms) from other units or other spaces in a building. The STC rating requirements for interior wall and floor assemblies are intended to limit the transmission of airborne noise between spaces. The NBC does not mandate any requirements for the control of impact noise transmission through floor assemblies. Footsteps and other impacts can cause severe annoyance in multifamily residences. Builders concerned about quality and reducing occupant complaints will ensure that floors are designed to minimize impact transmission.

Beyond conforming to the minimum requirements of the NBC in residential occupancies, designers can also establish acoustic ratings for design of non-residential projects and specify materials and systems to ensure the building performs at that level. In addition to limiting transmission of airborne noise through internal structural walls and floors, flanking transmission of sound through perimeter joints and sound transmission through non-structural partition walls should also be considered during the acoustical design.

Further information and requirements related to STC, ASTC and IIC ratings are provided in Appendix A of the NBC in sections A-9.10.3.1. and A-9.11.. This includes, inter alia, Tables 9.10.3.1-A and 9.10.3.1.-B that provide generic data on the STC ratings of different types of wood stud walls and STC and IIC ratings for different types of wood floor assemblies, respectively. Tables A-9.11.1.4.-A to A-9.11.1.4.-D present generic options for the design and construction of junctions between separating and flanking assemblies. Constructing according to these options is likely to meet or exceed an ASTC rating of 47 that is mandated by the NBC. Table A-Table 9.11.1.4. presents data about generic floor treatments that can be used to improve the flanking sound insulation performance of lightweight framed floors, i.e., additional layers of material over the subfloor (e.g. concrete topping, OSB or plywood) and finished flooring or coverings (e.g., carpet, engineered wood).

Combustible construction

The provision of fire safety in a building is a complex matter; far more complex than the relative combustibility of the main structural materials used in a building. To develop safe code provisions, prevention, suppression, movement of occupants, mobility of occupants, building use, and fuel control are but a few of the factors that must be considered in addition to the combustibility of the structural components.

Fire-loss experience shows that building contents play a large role in terms of fuel load and smoke generation potential in a fire. The passive fire protection provided by the fire-resistance ratings on the floor and wall assemblies in a building assures structural stability in a fire. However, the fire-resistance rating of the structural assemblies does not necessarily control the movement of smoke and heat, which can have a large impact on the level of safety and property damage resulting from fire.

The National Building Code of Canada (NBC) categorizes wood buildings as ‘combustible construction’. Despite being termed combustible, common construction techniques can give wood frame construction fire-resistance ratings up to two hours. When designed and built to code requirements, wood buildings provide the same level of life safety and property protection required for comparably sized buildings defined under the NBC as ‘noncombustible construction’.

Wood has been used for virtually all types of buildings, including; schools, warehouses, fire stations, apartment buildings, and research facilities. The NBC sets out guidelines for the use of wood in applications that extend well beyond the traditional residential and small building sector. The NBC allows wood construction of up to six storeys in height, and wood cladding for buildings designated to be of noncombustible construction.

When meeting the area and height limits for the various NBC building categories, wood frame construction can meet the life safety requirements by making use of wood-frame assemblies (usually protected by gypsum wallboard) that are tested for fire-resistance ratings. The allowable height and area restrictions can be extended by using fire walls to break a large building area into smaller separate building areas.

The recognized positive contribution to both life safety and property protection which comes from the use of automatic sprinkler systems can also be used to increase the permissible area of wood buildings. Sprinklers typically operate very early in a fire thereby quickly controlling the damaging effects. For this reason, the provision of automatic sprinkler protection within a building greatly improves the life safety and property protection prospects of all buildings including those constructed of noncombustible materials.

The NBC permits the use of ‘heavy timber construction’ in buildings where combustible construction is required to have a 45-minute fire-resistance rating. This form of heavy timber construction is also permitted to be used in large noncombustible buildings in certain occupancies. To be acceptable, the components must comply with minimum dimension and installation requirements. Heavy timber construction is afforded this recognition because of its performance record under actual fire exposure and its acceptance as a fire-safe method of construction. In sprinklered buildings permitted to be of combustible construction, no fire-resistance rating is required for the roof assembly or its supports when constructed from heavy timber. In these cases, a heavy timber roof assembly and its supports would not have to conform to the minimum member dimensions stipulated in the NBC.

Mass timber elements may also be used whenever combustible construction is permitted. In those instances, however, such mass timber elements need to be specifically designed to meet any required fire-resistance ratings.

 

NBC definitions:

Combustible means that a material fails to meet the acceptance criteria of CAN/ULC-S114, “Test for Determination of Non-Combustibility in Building Materials.”

Combustible construction means that type of construction that does not meet the requirements for noncombustible construction.

Heavy timber construction means that type of combustible construction in which a degree of fire safety is attained by placing limitations on the sizes of wood structural members and on thickness and composition of wood floors and roofs and by the avoidance of concealed spaces under floors and roofs.

Noncombustible construction means that type of construction in which a degree of fire safety is attained by the use of noncombustible materials for structural members and other building assemblies.

Noncombustible means that a material meets the acceptance criteria of CAN/ULC-S114, “Test for Determination of Non-Combustibility in Building Materials.”

 

For further information, refer to the following resources:

National Building Code of Canada

CAN/ULC-S114 Test for Determination of Non-Combustibility in Building Materials

Wood Design Manual 2017

Encapsulated mass timber construction

In addition to combustible, heavy timber and noncombustible construction, a new construction type is presently being considered for inclusion into the National Building Code of Canada (NBC). Encapsulated mass timber construction (EMTC) is proposed to be defined as the “type of construction in which a degree of fire safety is attained by the use of encapsulated mass timber elements with an encapsulation rating and minimum dimensions for the structural timber members and other building assemblies.” EMTC is neither ‘combustible construction’ nor ‘heavy timber construction’ nor ‘noncombustible construction’, as defined within the NBC.

EMTC is required to have an encapsulation rating. The encapsulation rating is the time, in minutes, that a material or assembly of materials will delay the ignition and combustion of encapsulated mass timber elements when it is exposed to fire under specified conditions of test and performance criteria, or as otherwise prescribed by the NBC. The encapsulation rating for EMTC is determined through the ULC S146 test method.

In order for structural wood elements to be considered ‘mass timber’, they must meet minimum size requirements, which are different for horizontal (walls, floors, roofs, beams) and vertical (columns, arches) load-bearing elements and dependent on the number of sides that the element is exposed to fire.

EMTC construction in Canada is expected to be limited to a height of twelve-storeys, that is, the uppermost floor level may be a maximum of 42 m (137 ft) above the first floor. An EMTC building must be sprinklered throughout according to NFPA 13 and it is likely that some mass timber will also be able to be exposed in the suites. All EMTC elements are expected to have a minimum two-hour fire resistance rating and the building floor area to be limited to 6,000 m2 for Group C occupancy and 7,200 m2 for Group D occupancy.

There are restrictions on the use of exterior cladding elements in EMTC, as well as other restrictions on the use of; combustible roofing materials, combustible window sashes and frames, combustible components in exterior walls, nailing elements, combustible flooring elements, combustible stairs, combustible interior finishes, combustible elements in partitions, and concealed spaces.

If any encapsulation material is damaged or removed, it will be required to be repaired or replaced so that the encapsulation rating of the materials is maintained.

Additionally, requirements related to construction site fire safety are to be applied to construction access, standpipe installation and protective encapsulation.

EMTC and its related provisions are anticipated to be included in the NBC 2020.

 

NBC definitions:

Combustible means that a material fails to meet the acceptance criteria of CAN/ULC-S114, “Test for Determination of Non-Combustibility in Building Materials.”

Combustible construction means that type of construction that does not meet the requirements for noncombustible construction.

Heavy timber construction means that type of combustible construction in which a degree of fire safety is attained by placing limitations on the sizes of wood structural members and on thickness and composition of wood floors and roofs and by the avoidance of concealed spaces under floors and roofs.

Noncombustible construction means that type of construction in which a degree of fire safety is attained by the use of noncombustible materials for structural members and other building assemblies.

Noncombustible means that a material meets the acceptance criteria of CAN/ULC-S114, “Test for Determination of Non-Combustibility in Building Materials.”

 

For further information, refer to the following resources:

ULC S146 Standard Method of Test for the Evaluation of Encapsulation Materials and Assemblies of Materials for the Protection of Mass Timber Structural Members and Assemblies

Fire performance of mass-timber encapsulation methods and the effect of encapsulation on char rate of cross-laminated timber (Hasburgh et al., 2016)

CAN/ULC-S114 Test for Determination of Non-Combustibility in Building Materials

NFPA 13 Standard for the Installation of Sprinkler Systems

Mass Timber
Mass Timber
Glulam
Glulam
Solid-Sawn Heavy Timber
Plank Decking
Tall Wood Buildings
Tall Wood Buildings – Research
Mid-Rise Buildings – Research
Climate Change
Codes & Standards
Acoustics
Combustible construction
Encapsulated mass timber construction
Mass Timber

Mass Timber

Advancements in wood product technology and systems are driving the momentum for innovative buildings in Canada. Products such as cross-laminated timber (CLT)...
Glulam

Glulam

Glulam (glued-laminated timber) is an engineered structural wood product that consists of multiple individual layers of dimension lumber that are glued together under...

Solid-Sawn Heavy Timber

Solid-sawn heavy timber members are predominantly employed as the main structural elements in post and beam construction. The term ‘heavy timber’ is used to describe...

Plank Decking

Plank decking may be used to span farther and carry greater loads than panel products such as plywood and oriented strand board (OSB). Plank decking is often used where the...

Tall Wood Buildings

With advanced construction technologies and modern mass timber products such as glued-laminated timber, cross-laminated timber and structural composite lumber, building tall...

Tall Wood Buildings – Research

Tests Current research includes the World’s largest mass timber fire test – click here for updates on the test results currently being conducted https://firetests.cwc.ca/...

Mid-Rise Buildings – Research

Studies General “The Historical Development of the Building Size Limits in the National Building Code of Canada“, by Sereca for CWC (2015)  (17 Mb) Reports produced...

Climate Change

Concerns about climate change are encouraging decarbonization of the building sector, including the use of construction materials responsible for fewer greenhouse gas (GHG)...

Codes & Standards

BUILDING CODES & STANDARDS (THE REGULATORY SYSTEM) The construction industry is regulated through building codes which are informed by: Design standards that provide...

Acoustics

Wood is composed of many small cellular tubes that are predominantly filled with air. The natural composition of the material allows for wood to act as an effective...

Combustible construction

The provision of fire safety in a building is a complex matter; far more complex than the relative combustibility of the main structural materials used in a building. To...

Encapsulated mass timber construction

In addition to combustible, heavy timber and noncombustible construction, a new construction type is presently being considered for inclusion into the National Building Code...

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