![]() When retrofitting the cripple wall, take a look at the thermal, air, and moisture control layers these provide the environmental separation that is the basis for all thermal efficiency. (Blocking appears white in drawing should be made of dimensional lumber.) (Source: Building Science Corporation). For seismic retrofit of crawlspaces with posts and piers, add cross bracing to posts add cross bracing and solid blocking between floor joists. Vented crawlspace cripple wall has seismic retrofits – plywood is added on to the interior of cripple walls and fastens to extra blocking added at sill plate and connected to foundation with new anchor bolts (Source: Building Science Corporation).įigure 3. (The blocking is shown in Figure 3 as the white boxes with black outlines between the floor joists.) The solid wood blocking prevents the floor joists from racking or rolling sideways. Floor framing should also have solid blocking of dimensional lumber installed between the floor joists. If there are interior posts and piers, additional bracing should be provided by installing cross bracing from the post to the floor beam on both sides of the posts. ![]() It may be necessary to add sill blocking if the interior faces of the existing studs are not flush with the interior face of the existing foundation sill. In this manner, the wall and floor diaphragms are connected to each other and to the foundation. Further note the foundation sill plate is connected to the concrete foundation with a foundation anchor bolt. Also, note that it is recommended that cripple wall retrofits have structural wood sheathing on both sides. In the retrofit of crawlspace foundations with cripple walls, the structural connection of the continuous exterior wood sheathing (plywood or oriented strand board ) to the foundation sill plate is necessary. The following issues should be addressed to improve the ability of new and existing homes with crawlspace foundation cripple walls to resist seismic activity.įigure 2 illustrates a construction or retrofit approach for a vented crawlspace foundation with a cripple wall. To withstand seismic stresses, the structural elements should be connected to each other and to the foundation.Īlthough unrelated to earthquake resistance, when retrofitting a foundation to make it more earthquake resistant, the foundation should also be assessed to see if the insulation, air sealing, and moisture protection could be improved to make the home more thermally efficient and durable. These lateral loads (“shear”) and uplift forces due to ground movement need to be transferred to the ground to minimize the likelihood of the building being pulled apart. Most of the damage to a building during an earthquake is caused by lateral movements, which disconnect the house from its foundation. How to strengthen cripple walls with plywood panels (Source: IBHS 2001).Įarthquakes are a major threat to the structural integrity of homes. A cripple wall is a short wall that rests on the foundation and supports the floor and exterior walls (Figure 1). This guide describes options for providing seismic and thermal resistance for homes with a “cripple” wall crawlspace foundation.
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