Pitched concrete roof

[smiles]

is it possible to have a poured concrete pitched roof? I've heard it can be done but my schoolboy physics tell me not possible.

what is the maximum slope/gradient that can be poured?
what sort of spans of roof can be covered without internal column supports?
is it a separate pour than the walls or all in one go?

Love to hear some thoughts on this and any links to further info.

[bkvanbek]

I use Lite-Deck for cast-in-place floor systems, instead of pre-cast. There are others, such as AmDeck and Insul-deck. But we like Lite-deck best for most applications.

I have not used a cast in place system for a pitched roof but I would think 4/12 is possible.

30' MAPS are easy but more is possible.

The engineers will want the top two feet of the walls poured with the floor/roof.

[smiles]

How wound you secure a membrane roof to a concrete deck? I've heard mechanical fixing can lead to late failure in the concrete.

[bkvanbek]

I am not a roofer, but I would glue a 80mil EPDM or thermoplastic membrane to the concrete. And maybe cover it with another 2" of concrete. Without the exposure to ultra violet light the membrane may last indefinitely and on a almost flat roof it would make a hell of a patio.

[smiles]

excellent idea. I hadn't thought of the concrete on top, to both protect the membrane and create a great outside space. Respect is due. Have you ever heard of people doing similar?

[bkvanbek]

We were in the design process of a contemporary house with all concrete floor systems and roof. But it was pricey, so the homeowner went right past the "sweet spot" of ICFs and last I heard was going to build a crappy wood framed house.

I would check with the membrane manufacturers, but the sun is the leading cause of the deterioration of roofing. And with concrete over the membrane I don't think wind would touch it.