With five-story wood frame construction permitted in several jurisdictions in the United States, designers are looking for a wall system to address the dimensional stability challenges as well as the higher vertical loads that can be applied in these structures. TimberStrand® LSL wall plates provide an effective solution to these challenges.
Reduce Multiple Story Wall Shrinkage
The manufacturing process of TimberStrand® LSL results in a dry and stable finished product that has a moisture content (MC) of approximately 6-8%. Considering interior members of finished structures equilibrate to around 6-11%, product movement, if any, will be minimal.
Sawn lumber is usually dried to a maximum of 19% MC and once installed in a structure, it will also equilibrate to around 6-11% MC. A moisture content reduction from 19% to 10% means the resulting shrinkage of the wall plates over the entire structure will not be insignificant, especially when multiple stories are considered.
Using an example outlined by the Western Wood Products Association “Shrinkage Calculation for Multistory Wood Frame Construction Report No. 10”, the amount of shrinkage for a 4-story structure can be around 0.8″, with 0.3″ of that shrinkage coming from the plates alone. This means roughly 40% of the shrinkage is from the plates. (Note: This example assumes a conservative 19% kiln-dried lumber MC with 2x10 lumber floor joists)
Superior Compression Perpendicular to grain
As vertical loads are passed down the structure, significant loads are applied to the framing members, especially the wall studs. As a result, high compression perpendicular to grain stresses will occur in the wall plates, at times controlling the size and spacing of the wall studs. Compared to sawn lumber, TimberStrand® LSL has superior compression perpendicular to grain properties resulting in more efficient designs. The table below compares the compression perpendicular to grain properties of TimberStrand® LSL with some common sawn lumber products. These values are also representative of Trus Joist® StrandGuard® TimberStrand® LSL treated plate material (available in 1.3E and 1.5E grades).
Other attributes of TimberStrand® LSL that make it a good choice for wall plates:
- Available lengths up to 48 ft. means less chord splices with faster design and installation.
- Higher tensile strength than sawn lumber results in more efficient diaphragm chords.
- Every piece is straight and true to size requiring no sorting on the job site.
- Limited lifetime warranty.