Problem: Wall deformation caused by shrinkage.
As framing lumber dries, it shrinks and undergoes stresses that cause the wood members to warp, bow, cup, twist and check. Other symptoms of lumber drying are nail pops and drywall cracks.
Cause: Wet lumber.
Lumber can be excessively wet, either as purchased from the lumber supplier, or as a result of poor site storage and handling procedures. The generation of excessive moisture during the construction phases, drying of concrete, drywall mud, paint and moisture from temporary heating sources, can also increase the moisture loading in the framing lumber.
Solutions:
Improve purchasing procedures.
- Specify dry lumber with a moisture content not greater than 19% from your suppliers. Many lumberyards have lumber with very high moisture content. Select lumber carefully.
Improve site storage and handling of lumber as previously discussed.
Minimize extreme moisture generation during the construction phase.
- Avoid generating excessive moisture during construction by:
- providing as much natural and mechanical ventilation as possible during construction,
- avoiding the use of unvented propane or gas heaters during winter.
Implement corrective measures to ensure that all framing members are straight.
- Inspect the framing after it has been constructed to determine whether it is level, plumb and true. Use the following steps to correct problems.
- straighten bowed studs, crowns by saw-cutting the concave or hollow sides and driving in wedges; provide nailing scabs to reinforce the cut stud as shown in Figure 12.
Figure 12 - Using a wedge to straighten a bowed wall stud
- Provide blocking between studs that bow sideways as shown in Figure 13.
Figure 13 - Preventing Or Correcting Bowing Studs
- Although studs shrink very little in length, check that they all reach the top plates. If they do not, install hardwood shims to fill the space, do not use cedar shims - they are easily crushed and do not provide adequate bearing strength.