Ballasted Roof Dead Load
Ballasted Roof Dead Load
(OP)
What do you guys/gals typically use for a dead load for a ballasted roof.
Maybe I am misunderstanding the different built up roof types...
Usually I see 12 psf used for a ballasted roof. However ASCE7 gives 6psf for 5-ply felt and gravel and 5.5 for bituminous and gravel.
Is the difference in how the roof systems are constructed (the ballasted roof holds the membrane down)?
Maybe I am misunderstanding the different built up roof types...
Usually I see 12 psf used for a ballasted roof. However ASCE7 gives 6psf for 5-ply felt and gravel and 5.5 for bituminous and gravel.
Is the difference in how the roof systems are constructed (the ballasted roof holds the membrane down)?






RE: Ballasted Roof Dead Load
It's not perfect, but it is a sanity check to see if you are in the right ballpark.
Wadavis
E.I.T.
RE: Ballasted Roof Dead Load
A loose ballasted roof (where you have 1 to 2 inches of gravel) is more on the order of 12 psf.
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RE: Ballasted Roof Dead Load
RE: Ballasted Roof Dead Load
A "ballasted roof" generally refers to a single ply roof membrane that is held in place against wind uplift by loading the surface with either stone ballast or pavers. The membrane for such systems is usually not attached to the substrate, although some systems do have supplementary perimeter attachment. Since the ballast is the primary resistance to wind uplift, there has to be a lot of ballast installed on the roof. Most systems have 10 to 12 psf for ballast. If you do the wind uplift calcs, that's woefully deficient for higher wind load areas so if that's where you are, recommend against its use.
A fully adhered or mechanically fastened single ply roof system is very light. Most of them that are commonly installed these days (PVC, TPO or similar membranes) only exert about 2 psf in additional dead load. They have no gravel surfacing and no supplementary ballast.
If the roof membrane is a modified bitumen system with ceramic granule surfacing, use about 4 psf for the loading, since those systems use heavier membranes that are bonded to the substrate, but do not have aggregate ballast.
RE: Ballasted Roof Dead Load
EIT
www.HowToEngineer.com
RE: Ballasted Roof Dead Load
RE: Ballasted Roof Dead Load