What SPF lumber is, how to read grade stamps, what S-DRY and KD mean, and when to choose something other than SPF for your Alberta project.
What is SPF?
SPF stands for spruce-pine-fir. It is a group of species, including spruce, lodgepole pine and fir, that have similar strength and appearance and are milled and sold together. In Western Canada it is the standard framing lumber for walls, floors and roofs.
Why it is used so widely
- Good strength for its weight, which makes it practical to frame with.
- Easy to cut, nail and screw.
- Widely available in standard sizes, so it is easy to plan around.
Reading the grade stamp
Each piece carries a stamp showing the mill, the species group (S-P-F), the grade and how dry it is. Common grades for framing include Select Structural, No.1 and No.2, and Stud grade for wall studs.
What S-DRY and KD mean
- S-DRY means surfaced dry, dried to a maximum of 19% moisture content.
- KD means kiln-dried, dried in a kiln to a controlled moisture content.
- Drier lumber shrinks and twists less after it is built into a wall or floor.
Studs for 8 ft walls
Precision end-trimmed (PET) studs cut for standard 8 ft walls are 92-5/8 in (2350 mm) long, which lets you build a wall with a single bottom plate and double top plate to the standard height.
When to choose something else
- Ground contact or constant moisture: use pressure-treated lumber.
- Exposed exterior wood you want to leave natural: consider treated lumber or a naturally durable species, and seal it.
- Long spans and heavy loads: ask about engineered beams such as LVL or glulam.
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