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Roof reports and MinimumDead Load Question

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Apr 18, 1999 6:30 PM
>From the Offices
of Dennis S. Wish, PE
1. To the best of anyones knowledge, is there a minimum roof dead load called 
out in the UBC or BOCA codes for assume in residential design?
2. Is there a minimum dead load to assume for the design of plated roof 
trusses (Gang-nail type trusses) when used for residential design (like 10 
psf top chord and 10 psf bottom chord).
3. What weight is assumed for Cedar Shake (Split shake and not shingle)? Is 
this weight assumed to be dry weight or the weight of the shake when wet?

I have to recommend if a client can change from a Shake roof (with plywood 
sheathing) to a lightweight tile. Disregarding the effect of the additional 
weight on lateral resistance (typically wind will control in one direction, 
seismic in the other) I have inspected the roof trusses which appear to be 
very well built and capable (by inspection) of at least a 10 psf top chord 
load and a 10 psf ceiling load.

Although this is one of the easier professional opinions for me to make, a 
recent post had me questioning if there is a minimum required dead load to 
use as there appears to be if  a Compo roof is used (3 layers). 

Any opinions?

Dennis S. Wish, PE
Structural Engineering Consultant