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Why should I worry about wall strength?
Your walls are the main structural component of your home. In wood
frame construction, the weight of the roof and any snow on the roof
push down on the walls with a compressive force. Strong winds and
wind gusts impose lateral loads onto your house walls that tend
to distort the walls with a shearing force. Building codes require
that walls be designed to withstand these loads. However, when walls
are built to minimum standards, while safe, you may sense wall creaking
during high winds or shaking when doors are slammed or the kids
are actively romping about.
 What
is a shearing force?
A shearing force on a wall tends to distort the wall from its original
shape as a rectangle into a parallelogram. To test a wall's resistance
to the shear forces imposed by wind loading, engineers use a "racking
test." An 8ft. x 8ft model wall is built and placed in a large frame.
The base of the wall is secured to the frame and a horizontal (lateral)
force is applied at one upper corner. The force increases in 400
lb increments until the wall structure fails.
What is the effect of Pella Roofing & Insulation's Polyurethane
Foam insulation?
In a series of racking tests walls with and without spray-applied
polyurethane foam insulation were compared.
| Wall with No foam: |
800 lb racking load |
| Wall with Foam: |
2800 lb racking load |
This shows that wall with Spray polyurethane foam installed can
add up too 2000 lb of resistance to any shearing force. This again
shows why our foam is superior over other types of insulation.
When Pella Roofing & Insulation foam is sprayed into your
stud walls and fully adheres to the exterior sheathing and studs,
reinforcing both. With this added rigidity, there will be less
wall movement due to shaking and vibration. Additionally your
walls have greater than code required resistance to "Racking Events"
such as hurricanes or other strong wind situations.
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