Slide 27 of 67
Use the Proper Lumber Species
- Different lumbers have different strengths for holding the nails.
- The denser the lumber is, the better the nails will hold – this determines the strength of the shear wall
- It is very important to use the proper lumber species
- Figure on the left: The lumber of choice in California for new construction is usually douglas fir-larch. Shown here is the grade stamp for the douglas fir-larch.
- Figure on the right: Some hem-fir is used for pressure treated sill plates.
- Older buildings used foundation grade redwood for sill plates and some used redwood for all framing members.
- Shear walls constructed with hem-for or redwood are weaker than shear walls constructed with Douglas fir-larch.
- Why is it important to use the proper lumber species?
- Density of the lumber species determines how well the sheathing fasteners will hold.
- Shear walls constructed with lower density lumber do not hold fasteners as well as shear wall constructed with denser lumber.
- The Uniform Building Code requires an 18% strength reduction for walls built with the less-dense hem-fir and a 35% reduction for open grain redwood.
- The following table shows some of the different allowable shears based on the species of the lumber framing.