Douglas Fir KD12
Finish state · default condition
KD12 = kiln-dried to 12 % MC
Reference 12 % moisture condition used for published clear-wood properties and for interior joinery, flooring and millwork.
Values for the KD12 condition
Other Douglas Fir tempers and conditions
Douglas Fir is listed in 4 conditions; see the grade overview at Douglas Fir.
Compare all 4 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Douglas-fir laminated veneer lumber | Engineered veneer laminate for beams and headers: knots dispersed, so stiffness and strength are higher and far less variable than sawn lumber. | — | 55 | — | — | 0.13 W/m·K |
Unseasoned, MC above fibre saturation | Freshly sawn/wet-use lumber: heaviest, softest and lowest strength — use only where drying shrinkage is designed for. | — | 75 | — | — | 0.2 W/m·K |
KD19 / S-DRY | Standard framing/dimension-lumber condition sold as S-DRY or KD-HT; the basis for most building-code design values. | — | 90 | 0.8 | — | 0.13 W/m·K |
KD12DefaultThis page Kiln-dried to 12 % MC | Reference 12 % moisture condition used for published clear-wood properties and for interior joinery, flooring and millwork. | — | 105 | 1 | — | 0.12 W/m·K |
What is Douglas Fir KD12?
Douglas Fir KD12 is Douglas Fir supplied in the KD12 condition — reference 12 % moisture condition used for published clear-wood properties and for interior joinery, flooring and millwork. Douglas Fir KD12 has a tensile strength of 105 MPa (15.2 ksi), stronger than 91% of natural material grades. Elongation at break is 1% and the elastic modulus is 13.4 GPa (1.94 Msi). Douglas Fir KD12 has a density of 0.48 g/cm³ (0.0173 lb/in³), lighter than 76% of natural material grades.
Advantages
- Lightweight — 0.48 g/cm³ (0.0173 lb/in³), better than 76% of natural material grades
Limitations
- Limited service temperature — 65°C (149 °F), worse than 88% of natural material grades
- Low fracture toughness — 0.4 MPa·√m (0.364 ksi·√in), worse than 86% of natural material grades
Douglas Fir KD12 properties
Typical room-temperature values for Douglas Fir KD12; 10 are specific to this condition. Other listed values are Douglas Fir reference data and may not represent this condition. Bars are the position among natural material grades.
Physical2
Douglas Fir KD12 has a density of 0.48 g/cm³ (0.0173 lb/in³), lighter than 76% of natural material grades.
Mechanical10
Douglas Fir KD12 has a tensile strength of 105 MPa (15.2 ksi), stronger than 91% of natural material grades. Elongation at break is 1% and the elastic modulus is 13.4 GPa (1.94 Msi).
Thermal5
Douglas Fir KD12 is rated for continuous service to 65°C (149 °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 µm/m·K (2.22 µin/in·°F).
Electrical2
Douglas Fir KD12 is an electrical insulator with a dielectric strength of 5 kV/mm (127 V/mil) and a resistivity of 1×10⁹ Ω·m.
Chemical & Environmental1
Corrosion resistance is fair (50/100), better than 63% of natural material grades.
Sustainability4
Producing a kilogram of Douglas Fir KD12 takes about 10 MJ of energy and emits 0.35 kg of CO₂ — less than 56% of natural material grades. Typical recycled content is 5%.
Manufacturability2
Douglas Fir KD12's machinability is very good (80/100, worse than 52% of natural material grades).
Common Calculations4
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with Douglas Fir KD12
Is Douglas Fir easy to machine?
Saws, planes and routs easily with carbide tooling; hard latewood bands and resin cause tear-out and pitch build-up, so use sharp tools, high rake and periodic blade cleaning.
Can Douglas Fir be welded?
Not weldable — joined by nails, screws, split-ring/plate connectors, or PVA/PUR/resorcinol and phenolic adhesives (good bonding, but degrease resin-rich surfaces).
Can Douglas Fir be formed, bent or molded?
Poor steam-bending species (low bend ratio); shape by lamination of thin veneers/laminae as in glulam and LVL, allowing 3–5 % tangential shrinkage on drying.
What surface finishes work on Douglas Fir?
Sands well but raises grain and takes stain unevenly due to strong earlywood/latewood contrast — use conditioner or pigmented primer; heartwood resists preservative pressure treatment and usually needs incising.
Douglas Fir 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 |
|---|---|---|
| celluloseoven-dry wood basis | 44 – 50 | 47 |
| hemicellulosemainly galactoglucomannan | 18 – 25 | 22 |
| ligninguaiacyl-type softwood lignin | 26 – 31 | 28 |
| extractives (resins, terpenes, phenolicshigher in heartwood; causes resin pockets | 2 – 6 | 3.5 |
| ash (inorganics) | 0.2 – 0.6 | 0.3 |
Douglas Fir KD12 — frequently asked
What is Douglas Fir KD12 used for?
Douglas Fir KD12 is typically used for structural framing, glulam beams, plywood face veneer, marine spars and heavy timber construction. In short: stiffest common framing softwood; base species for glulam and LVL; poor steam-bending species.
What is the tensile strength of Douglas Fir KD12?
Douglas Fir KD12 has a typical tensile strength of 105 MPa (15.2 ksi) — stronger than 91% of natural material grades. Strength varies by condition: see the 4 listed tempers.
Is Douglas Fir KD12 easy to machine?
Yes — machinability is rated very good (80/100, worse than 52% of natural material grades). Saws, planes and routs easily with carbide tooling; hard latewood bands and resin cause tear-out and pitch build-up, so use sharp tools, high rake and periodic blade cleaning.
Can Douglas Fir KD12 be welded?
Not weldable — joined by nails, screws, split-ring/plate connectors, or PVA/PUR/resorcinol and phenolic adhesives (good bonding, but degrease resin-rich surfaces).
What surface finishes work on Douglas Fir KD12?
Sands well but raises grain and takes stain unevenly due to strong earlywood/latewood contrast — use conditioner or pigmented primer; heartwood resists preservative pressure treatment and usually needs incising.
Can Douglas Fir KD12 be formed, bent or molded?
Poor steam-bending species (low bend ratio); shape by lamination of thin veneers/laminae as in glulam and LVL, allowing 3–5 % tangential shrinkage on drying.
What is the maximum service temperature of Douglas Fir KD12?
Douglas Fir KD12 is rated for continuous use to about 65°C (149 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
Sources
- Wood Handbook — Wood as an Engineering Material (FPL-GTR-190) — USDA Forest Products Laboratory (2010)
- ASTM D2555 — Establishing Clear Wood Strength Values — ASTM International (2017)
- ASTM D143 — Standard Test Methods for Small Clear Specimens of Timber — ASTM International (2022)
- EN 13556 — Nomenclature of timbers used in Europe (code PSMe) — CEN (2003)
- LVL Product Guide / Design Properties — APA – The Engineered Wood Association (2021)
- Inventory of Carbon & Energy (ICE) v3 — sawn softwood — Circular Ecology (2019)
Property data is compiled from published supplier and standards handbooks and normalised for comparison. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.