CLT
ASTM ANSI/APA PRG 320 · EN 16351
CLT (cross-laminated timber) is a mass-timber panel of orthogonally stacked and bonded lumber lamellas, produced to EN 16351 and ANSI/APA PRG 320 in strength classes such as CL24h, CL32h, PRG320-E1 and V2, plus hardwood layups.
Reference datasheet — CLT is not in the instant-quote catalog. Upload your part and an engineer will quote it in this grade or suggest the closest stocked equivalent.
Values for the CL24h condition
CLT tempers and conditions
CLT is supplied in 5 conditions, soft to hard. CL24h is the default FabDigit quotes; the values on this page are for it.
Compare all 5 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
PRG 320 Grade E1 | North American stock layup: machine-stress-rated Spruce-Pine-Fir, widest availability from US/Canadian plants. | 15 | 0.8 | 0.12 W/m·K | ||
PRG 320 Grade V2 | Choose where higher density, better rolling shear and screw/connector capacity are needed (heavy floors, connections). | 15 | 0.9 | 0.13 W/m·K | ||
CL24hDefault Spruce CLT, homogeneous C24 lamellas | European default: PEFC/FSC spruce-fir lamellas graded C24, PUR-bonded, for floors, walls and roofs. | 16 | 0.9 | 0.12 W/m·K | ||
Spruce CLT, homogeneous C30/C32 lamellas | Pick when spans or wall loads govern and machine-graded high-stiffness lamellas justify the price premium. | 20 | 0.9 | 0.12 W/m·K | ||
Hardwood CLT | Specialty high-capacity panels for slender slabs, exposed architectural use or heavy point loads; costlier and heavier. | 25 | 1.1 | 0.17 W/m·K |
What is CLT?
CLT (cross-laminated timber) is a mass-timber panel of orthogonally stacked and bonded lumber lamellas, produced to EN 16351 and ANSI/APA PRG 320 in strength classes such as CL24h, CL32h, PRG320-E1 and V2, plus hardwood layups. Engineers specify it for two-way structural capacity at 0.47 g/cm3 density with about 11 GPa modulus and 16 MPa tensile strength, delivered as prefabricated wall, floor and roof panels cut to size. Thermal conductivity is 0.12 W/m-K and maximum service temperature 55 C; panels must be detailed for service class 1-2, protected from wetting on site and designed with charring allowance for fire. LVL is the alternative where a linear beam rather than a plate is needed. CLT has a density of 0.47 g/cm³ (0.017 lb/in³), lighter than 80% of natural material grades. CLT has a tensile strength of 16 MPa (2.32 ksi), weaker than 61% of natural material grades. Elongation at break is 0.9% and the elastic modulus is 11 GPa (1.6 Msi).
What is CLT used for?
- Mass timber walls/floors
- Multi-story buildings
- Prefabricated modules
- Roof panels
- Bridges
Advantages
- Easy to machine — 92/100, better than 97% of natural material grades
- Lightweight — 0.47 g/cm³ (0.017 lb/in³), better than 80% of natural material grades
Limitations
- Limited service temperature — 55°C (131 °F), worse than 96% of natural material grades
- Low fracture toughness — 0.4 MPa·√m (0.364 ksi·√in), worse than 86% of natural material grades
CLT properties
Typical room-temperature values for CLT-CL24h; bars are the position among natural material grades.
Physical2
CLT has a density of 0.47 g/cm³ (0.017 lb/in³), lighter than 80% of natural material grades.
Mechanical9
CLT has a tensile strength of 16 MPa (2.32 ksi), weaker than 61% of natural material grades. Elongation at break is 0.9% and the elastic modulus is 11 GPa (1.6 Msi).
Thermal5
CLT is rated for continuous service to 55°C (131 °F). It conducts heat at 0.12 W/m·K (0.0693 BTU/hr·ft·°F), worse than 70% of natural material grades. Thermal expansion is 4.5 µm/m·K (2.5 µin/in·°F).
Electrical2
CLT is an electrical insulator with a dielectric strength of 4 kV/mm (101.6 V/mil) and a resistivity of 1×10⁸ Ω·m.
Chemical & Environmental1
Corrosion resistance is fair (45/100), better than 53% of natural material grades.
Sustainability3
Producing a kilogram of CLT takes about 9 MJ of energy and emits 0.42 kg of CO₂ — less than 65% of natural material grades. Typical recycled content is 2%.
Manufacturability2
CLT's machinability is excellent (92/100, better than 97% of natural material grades).
Common Calculations4
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Working with CLT
Is CLT easy to machine?
CNC-routed and drilled easily with carbide spiral tooling and strong dust extraction; openings, service chases and connector pockets are cut in the plant to ±1–2 mm.
Can CLT be welded?
Not weldable — panels are joined by self-tapping screws, splines/half-lap panel joints, glued-in rods and steel brackets.
Can CLT be formed, bent or molded?
Formed only during production by cold-pressing crossed lamella layers (0.6–1.0 MPa, PUR); curved panels need pre-bent lamellas, no post-forming.
CLT chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| cellulosesoftwood lamella, oven-dry basis | 40 – 45 | 42 |
| hemicellulose | 24 – 30 | 27 |
| lignin | 25 – 31 | 28 |
| extractives + ashresins, terpenes, minerals | 1 – 4 | 2.5 |
| structural adhesive (PUR or MUF)EN 15425 / EN 301 bond lines | 0.3 – 1.5 | 0.6 |
| moisture (as delivered)12 ± 3 % MC per EN 16351 | 9 – 15 | 12 |
What surface finishes work on CLT?
Sand/plane for visual-quality faces, then UV/water-based clear coat, stain or fire-retardant coating; end grain and exposed faces must be sealed against moisture and detailed for service class 1–2.
Equivalent designations
Standards and trade names that resolve to CLT in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- ASTM
- ANSI/APA PRG 320
- EN / DIN / Werkstoff-Nr.
- 16351
How much does CLT cost?
CLT is a standard-cost natural material ($$), cheaper than about 71% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
CLT — frequently asked
What is CLT used for?
CLT is typically used for mass timber walls/floors, multi-story buildings, prefabricated modules, roof panels and bridges. In short: two-way mass-timber plate; highest panel machinability rating; prefabricated to millimetre tolerance.
What is the tensile strength of CLT?
CLT has a typical tensile strength of 16 MPa (2.32 ksi) — weaker than 61% of natural material grades. Strength varies by condition: see the 5 listed tempers.
Is CLT easy to machine?
Yes — machinability is rated excellent (92/100, better than 97% of natural material grades). CNC-routed and drilled easily with carbide spiral tooling and strong dust extraction; openings, service chases and connector pockets are cut in the plant to ±1–2 mm.
Can CLT be welded?
Not weldable — panels are joined by self-tapping screws, splines/half-lap panel joints, glued-in rods and steel brackets.
What surface finishes work on CLT?
Sand/plane for visual-quality faces, then UV/water-based clear coat, stain or fire-retardant coating; end grain and exposed faces must be sealed against moisture and detailed for service class 1–2.
Can CLT be formed, bent or molded?
Formed only during production by cold-pressing crossed lamella layers (0.6–1.0 MPa, PUR); curved panels need pre-bent lamellas, no post-forming.
What is the maximum service temperature of CLT?
CLT is rated for continuous use to about 55°C (131 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
How much does CLT cost?
CLT is a standard-cost natural material ($$), cheaper than about 71% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
Sources
- EN 16351 Timber structures — Cross laminated timber — Requirements — CEN (2021)
- ANSI/APA PRG 320 Standard for Performance-Rated Cross-Laminated Timber — APA – The Engineered Wood Association (2019)
- EN 338 Structural timber — Strength classes — CEN (2016)
- Wood Handbook — Wood as an Engineering Material (FPL-GTR-190) — USDA Forest Products Laboratory (2010)
- CLT Handbook (US Edition) — FPInnovations / Binational Softwood Lumber Council (2013)
- CLT panel technical data / ETA declarations (KLH, Stora Enso, Binderholz) — producers (2023)
- Inventory of Carbon & Energy (ICE) v3 — cross laminated timber — Circular Ecology (2019)
Property data is compiled from published supplier and standards handbooks and normalised for comparison; hardness values on non-Brinell scales are converted approximately for charting only. Manufacturability limits are FabDigit quote-engine defaults and may be relaxed by engineering review. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.