Roofing Systems for Flat Roof


Hi All,

We have a 500 sf walkable roof deck over the kitchen of a high-end residence we're building. The roofing is LVL joists, with a pywood diaphragm and wood sloping. It's currently under construction.

Our contractor is concerned that we make this roof bulletproof. The actual roofing surface will occasionally be walked on, and it will have pebbles and decking on it.

A number of people I've talked to have suggested putting a 3-ply (or 4-ply) modified bitumen up there. Others have suggested PVC roofing, which sounds like a very solid system to me.

Can someone explain what these two systems are, and what the advantages are? Any sense of which will work best in a pedestrian use over living space?

Mar 10, 08 6:55 pm

You could run two layers of bitumen perpendicular to each other.

And remember to paint it with reflective paint to minimize heat gain.

Mar 10, 08 6:58 pm  · 
el jeffe

a deck over a kitchen isn't the greatest adjacency - vent pipes and kitchen exhaust odors. but assuming you're somehow mitigating those 'features', you could use a TPO roof.

mod bit is frequently used for roofing because (depending on the local building trades) finding someone to repair a b/u roof is usually quite a bit easier (and cheaper) than a single-ply.

personally, i wouldn't use a mod bit under a walking surface.

what's 'wood sloping', btw? do you mean rip strips???

Mar 10, 08 7:19 pm  · 

membrane roof with pavers on pedestals? the project i'm working on is using this combo on balconies and decks.

Mar 10, 08 7:22 pm  · 

rip strips.

how's the durability of a single-ply (assuming you mean PVC) relative to 3-ply mod bit? Is that heat welded and UV-safe? What goes underneath it?

Mar 10, 08 7:24 pm  · 

in the old days they used canvas and molten lead.....but that will not fly today.

Mar 10, 08 7:28 pm  · 

I second the built up roof 2 / 3 ply and then the pavers on pedestals, I've been doing that for years and the pavers take a ton of abuse and protect the real roof below.

Mar 10, 08 9:01 pm  · 

mckinley flat roof repair hires spammers to go around advertising where they are not wanted. buyer beware.

Mar 18, 20 12:22 pm  · 

check out the CIM 1000 2-part urethane. and, of course, Hydrotech, who will warranty a dead flat roof for 20 years. these are more commercial products, but work really well.

Mar 18, 20 12:52 pm  · 

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