Pouring a concrete roof - GIF

[Frank S]

Hi Nova, That roof material sounds like foamed gypsum. I came across it in the late 70s , it was being used for both walls and roof. We had a chunk that was broken off by a lift truck, and used to toss it to a newbie ,he'd catch it thinking it weighed 20 lbs and just about hit himself in the head . It weighed about 2 lbs. Good times.😁

Foamed gypsum, yeah I remember that stuff. There was a company in SoCal that made faux boulders out of that and wire mesh, a rock the size of a piano might weigh 70 lbs they were hollow as well. I picked up a load of them to deliver to a place near lake Taho. I hefted a real stone that weighed about 50 lbs and handed it to the guy helping me. Here you take this one I'll get that one over there. When he saw me hoist it above my head and rest it on my shoulder like Charles Atlas I thought he was going to loose his mind.

[IAMSatisfied]

In the video, the rebar is laying directly on the foam-board... you want rebar to be at least a couple of inches or so from any surface of a pour for decent strength. Perhaps the workers will lift the rebar mat once they have enough concrete down... I've worked on slabs where this is practiced. It appears that this roof will be poured about 4" thick based on the "skylight" hole on the far right of the roof... if correct, that would be around 50 PSF static load... you need some decent roof framing for that. Tile roofs are often designed for a dead load of 15 PSF.

[bob_3000]

Hi Nova, That roof material sounds like foamed gypsum. I came across it in the late 70s , it was being used for both walls and roof. We had a chunk that was broken off by a lift truck, and used to toss it to a newbie ,he'd catch it thinking it weighed 20 lbs and just about hit himself in the head . It weighed about 2 lbs. Good times.

Classic, we used to do that with plastic display car battery, worked every time.