Mass Timber
Understanding mass timber.
A plain-language primer for architects and engineers specifying mass timber for the first time.
The Category
What is mass timber?
Mass timber is a family of engineered wood products that combine smaller pieces of lumber into large, structural elements — panels, beams, and columns strong enough to carry mid-rise and commercial buildings. It replaces concrete and steel with a renewable, carbon-storing material that can be left exposed as the finished surface.
DLT, CLT and GLT.
DLT
Dowel Laminated Timber
Softwood lamella joined by hardwood dowels — no glue, no metal. Strong single-direction spans and a beautiful exposed ceiling.
CLT
Cross Laminated Timber
Layers bonded crosswise for two-way spanning panels. Widely used for floors and shear walls, with adhesive between plies.
GLT
Glue Laminated Timber
Lamella glued into beams and columns for framed structures — the long-span workhorse of post-and-beam timber.
How it works
The structural logic of DLT.
Mass timber is most competitive in office, education, mid-rise residential, institutional and civic buildings — typically four to twelve storeys — wherever the exposed structure can also be the finished ceiling.
A one-way panel
Load travels in a single direction, along the lamellae, so all the wood fibre works efficiently in the span. Panel depth drives span capacity — a deeper panel spans further — while panel width is largely independent of structural performance.
Shallower than CLT
CLT alternates grain between layers for two-way behaviour, so some fibre always works across the grain, less efficiently. For a one-way floor or roof, DLT reaches the same capacity with a shallower section — less material and less weight per floor plate.
The practical implication
Where a CLT floor might need an 8¼-inch (210 mm) panel, DLT often achieves the same span at 7¼ inches (184 mm). Across a full floor plate, that difference in section depth and fibre volume compounds into meaningful cost and weight savings.
Who’s asking
Why mass timber. Why now.
The case for mass timber looks different depending on where you sit. Pick your seat.
Owners & developers
The business case is schedule and story.
Mass timber structures erect in a fraction of the time of cast-in-place concrete — no formwork, no cure time, and interior trades start work immediately — no drying time. A faster weather-tight building means earlier revenue. Exposed timber interiors lease faster and appraise as premium space: tenants can feel the difference the moment they walk in.
Why now: building codes permit taller timber buildings than ever, and at mid-rise heights the economics work. Embodied-carbon requirements are tightening on public and institutional procurement — a timber structure is the single biggest carbon line-item you can move. And insurers, once wary, now have a decade of performance data.
Engrained angle: Full-length panels up to 60 ft mean fewer pieces, fewer crane picks, faster floors. Talk to us while the budget is still taking shape — early design decisions capture most of the savings.
Architects
Structure and finish in one honest element.
DLT left exposed is the ceiling — warm, natural, and quiet in a way suspended ceilings never are. No glue lines, no metal fasteners: wood joined by wood. Acoustic profiles integrate absorption without cladding over the structure you just celebrated.
Why now: clients are asking for wood by name. Code changes have opened taller and larger timber buildings, and the supporting ecosystem — connections, acoustics, fire engineering — has matured from pioneering to routine.
Engrained angle: panels up to 60 ft run wall to wall in a single piece, and our appearance grades let you specify the finish by name. Send us your grid early and we’ll shape the panel layout around the architecture, not the other way around.
Structural engineers
A panel you can verify, not just trust.
DLT is a one-way system with predictable behaviour: CSA O86 design values, calculable char per the zero-strength-layer method, and now CSA O125:23 — the first Canadian production standard for mechanically laminated timber (MLT) — behind it. Every Engrained panel is manufactured with force-and-displacement monitoring on every single dowel, and ships with the complete QA record.
Why now: the standards landscape just matured. O125:23 gives MLT a certification pathway; our custom layup qualification is backed by full-scale bending tests, not extrapolation. You get tested stiffness data, published span tables, and a fabricator who can show you the force–displacement record behind every dowel.
Engrained angle: design-assist from schematic onward. Send loads, spans, and fire requirements — we return sized options with the numbers behind them.
Builders & GCs
Prefabrication that behaves like it on site.
Panels arrive finished, sequenced, and labelled — each one laser-etched with a QR code that confirms the piece, its specs, and its place in the erection order. Lighter than concrete: smaller cranes, fewer deliveries, no rebar, no waiting on concrete to cure. A dry site and a clean critical path.
Why now: skilled-labour scarcity rewards structures that install with small crews. Mass timber floors go down in days, not weeks — and every week of schedule is money.
Engrained angle: Full-length single pieces mean fewer picks per floor. Scan any panel and know exactly what you’re holding and where it goes. Ask us about erection sequencing support at tender stage.
Wherever you sit — the earlier we’re involved, the more we can offer.
Fire performance
Fire, in practice.
Mass timber burns slowly and predictably. Exposed softwood chars at about 0.65 mm per minute, and the char layer insulates the structural core behind it for the duration the assembly is designed to resist.
Calculable by design
The engineer calculates the residual cross-section after the design fire duration and confirms it still carries load. It is calculable, documented and reproducible — the basis for the 2-hour ratings assigned to tested DLT assemblies under ASTM E119 and CAN/ULC S101 at a minimum 6-inch (140 mm) panel depth.
Code pathways
Under the National Building Code of Canada, DLT panels ≥130 mm qualify as Heavy Timber. Encapsulated Mass Timber Construction allows exposed mass timber up to 12 storeys; exposed mass timber is permitted up to 6 storeys in certain occupancies.
Timber vs steel
Unprotected steel loses strength rapidly and unpredictably above 550 °C. Mass timber chars at a known rate, keeps a structural core, and gives fire crews a predictable building — a fire strategy you can read in the structure itself.
Building with it
Detailing for the site.
The details that decide a mass timber schedule are settled in design development, not at permit. Three to resolve early.
Services & MEPF (mechanical, electrical, plumbing, fire protection)
Chases — deliberate 4-to-12-inch (100–300 mm) gaps between panels — run parallel to the span to carry conduit, pipe and sprinkler mains, closed with profiled covers that keep the exposed ceiling. Vertical penetrations are CNC-machined in the shop from the coordinated 3D building model (BIM). Never field-cut structural panels without engineering review.
Floor build-ups & acoustics
A typical floor stacks exposed DLT → acoustic mat → a 2½-to-4-inch (65–100 mm) concrete topping. The topping delivers acoustic separation, the structural diaphragm and thermal mass at once. Tested assemblies reach sound transmission (STC) and impact (IIC) ratings in the mid-50s — enough for residential and office occupancies.
Connections
Connections are resolved between the engineer of record and the fabricator: concealed knife plates and timber rivets at bearings, screwed ledgers at cores, inclined screws for composite action. Bring the fabricator in at schematic design — late connection design is the most common source of delay.
Why Now
The moment for timber.
Recent National Building Code changes allow taller and larger timber buildings than ever before. At the same time, embodied-carbon targets are pushing teams away from concrete and steel, and clients increasingly ask for the warmth and calm of exposed wood. Mass timber sits precisely at that intersection.
860 kg
CO₂ stored per m³ of finished panel
≈350 kg
CO₂ emitted per m³ of structural concrete
A DLT floor plate carries a net-negative embodied-carbon number from day one; a concrete plate carries a large positive one. Environmental product declarations (EPDs) available per project for LEED v4.1 BD+C targets.
Design considerations.
Connections
Steel connectors and bearing details drive both cost and buildability — resolve them early with the fabricator.
Fire resistance
Mass timber chars predictably; sacrificial thickness gives a calculable fire-resistance rating for exposed members.
Acoustics
Plan floor build-ups and toppings to meet impact and airborne sound targets between occupancies.
Moisture management
Protect panels during transport and construction, and detail the envelope to keep timber dry in service.
Common questions
Questions specifiers ask.
Does mass timber burn?
Timber chars at a slow, predictable rate. The char layer insulates the structural core, giving a calculable fire resistance. DLT assemblies have been tested to 2-hour ratings under ASTM E119 and CAN/ULC S101 at a minimum 6-inch (140 mm) panel depth.
Can I modify DLT panels on site?
Yes. With no glue or metal fasteners, panels cut with standard saws. All penetrations should still be designed and documented by the engineer of record — field modifications to structural sections require review.
What about moisture?
SPF lamella is kiln-dried to 12–15% before pressing. A site moisture-management plan is developed with the GC. Properly detailed, mass timber performs well through Southern Ontario’s freeze-thaw cycles.
Is mass timber more expensive than concrete?
Upfront material cost is typically similar to or above concrete. The savings come from speed of erection, reduced crane time, no formwork, and the exposed structure doubling as finish. Whole-life comparisons usually favour mass timber.
How early should we engage a fabricator?
As early as schematic design. Connection design, MEPF coordination and panelization all feed back into the structure — the earlier we’re involved, the more value we add without changing anything.
A living material
Mass timber keeps the warmth and the carbon of the forest inside the building, long after the trees are milled.
Planning a mass timber project?
Tell us about your project. The earlier we’re involved in design development, the more we can offer.
Prefer email? hello@engrained.ca