Wood-framed parapet wall with 1:1 Brace on Roof
Wood-framed parapet wall with 1:1 Brace on Roof
(OP)
I am planning to design a 4-story wood-framed structure with a nominal 3'-6" parapet wall. If the wood bracing with sheathing displaces a triangular area of the roof about 3 feet wide by 3 feet tall, how should I approach the snow drift loads? The ASCE 7-05 ground snow is 30 psf.
Common sense says there will be no drift at the top of the brace since there is only about a 6" vertical projection above it. Take a look at the attached sketch.
Common sense says there will be no drift at the top of the brace since there is only about a 6" vertical projection above it. Take a look at the attached sketch.






RE: Wood-framed parapet wall with 1:1 Brace on Roof
Has anyone taken a look at this problem before?
RE: Wood-framed parapet wall with 1:1 Brace on Roof
That being said though, I think it is reasonable to assume that it is safe to subtract the snow load in the space taken up by the 1:1 sloped brace. I would still apply the remainder of the snow load as if the 1:1 braced wall was not there.
Mike McCann
MMC Engineering
RE: Wood-framed parapet wall with 1:1 Brace on Roof
Start the drift layout at the back of the parapet but where the height difference between top of parapet and top of structure (roof or cricket or whatever) is less than your base height, no drift would be added.
RE: Wood-framed parapet wall with 1:1 Brace on Roof
Garth Dreger PE - AZ Phoenix area
As EOR's we should take the responsibility to design our structures to support the components we allow in our design per that industry standards.