I’m building a large wood shop here in western North Carolina. I would like to use plywood box beams for the structual headers for all the rough openings. Most of the headers will be over modest windows but there is one header which will span a six foot overhead door and a three foot swing door. I’ve looked long and hard on the internet, but I can find only sidelong references to box headers, certainly nothing that pass muster for an inspection. Does anyone know of any definitive literature or design tables for sizing and constructing plywood box beams?
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Replies
"Elements of strength of materials"
Timeshencko and Young, Van Nostrand published I recall, book is on my workplace shelf.
My old 1960's text.
Probably any beginning structures text will have it as part of 'built up beams'.
Built a 36 foot span 3 ft deep with 3 ea 2x6 stringers and 1/2 ply webs for holding up second floor of brother's house 25 years ago, no sag.
edoit BTW. With glue, drywall screws are OK. for these.
Edited 10/31/2004 9:01 pm ET by JUNKHOUND
IRC code book covers them, and gives the allowable spans.
Joe H
Maybe so, but I can't find it. All I can find is tables for sawn lumber.
jim we use ply box beams whenever we can
they are spec'd in the IRC..
from your description i couldn't tell if the big span was 6' or 9'..
if i recall.. you can span 6' but probably not 9'..
natch.. if you get a PE to spec your box beam for you , you can probably span the 9'..
but you'll have to buy 10' plywood to do itMike Smith Rhode Island : Design / Build / Repair / Restore