Pouring a concrete roof - GIF

[Altair]

Pouring a concrete roof.




Previously:

Mat foundation pouring operation - photo
3D concrete printing
Concrete being pumped across construction site - GIF
Throwing concrete up onto a wall - GIF
Filling a concrete mixer from a distance - GIF

[nova_robotics]

A sloped concrete roof? I've never seen such a critter. What are the advantages of this? Wind uplift, I guess, but it seems you'd still need a weather-tight roofing system installed over top of the concrete. So why use concrete as opposed to other lighter and more cost effective materials? I'm genuinely curious.

[Wildwilly]

I'm sure that here in Canadastan we'll be doing it soon.....just to keep inflation from going through the roof!

[Frank S]

A sloped concrete roof? I've never seen such a critter. What are the advantages of this? Wind uplift, I guess, but it seems you'd still need a weather-tight roofing system installed over top of the concrete. So why use concrete as opposed to other lighter and more cost effective materials? I'm genuinely curious.

I'll give you lighter, but in some countries concrete is the most cost effective construction material there is. Once it is troweled out it will shed water just fine. It it is thick enough it will make a fair heat barrier against the sun

[Gadgeteer]

How about styrocrete?

[TrickieDickie]

It is for certain hail of any size will shatter on impact.

[nova_robotics]

It it is thick enough it will make a fair heat barrier against the sun

I disagree with you there. Concrete has an atrocious r value. Poured concrete is closer thermally to steel than any kind of insulation. It's the sitting down on a cold toilet seat of building materials. Generally we pour 4" over q-deck which I think is industry standard in North America, so assuming this pour is roughly the same thickness that'll get you an r-value for that whole roof of around 0.3.

Normally around here concrete roofs are specified with 4" of iso insulation laid on top for an r-value of 25, then the water-tight roofing system is installed over top of that. One single inch of iso insulation will get you an r-value of over 6. So one inch of iso insulates as much as 75 inches of concrete.

[nova_robotics]

How about styrocrete?

I worked on a building that was constructed somewhere between 1950-1970. It was an electrical house for a big mine hoist. It was the site of a natural disaster and part of our project was replacing the roof. Quite a large building by e-house standards, about 50 x 200. The roof was constructed out of pre-cast highly aerated panels. I think it might have been air-crete, or at least something similar. Very interesting material. I think it may have had some aluminum-oxide component, but it was largely concrete and air. It felt like aged styrofoam that had been left in the sun too long. You could cut it with your fingernails. It looks much lighter in color than concrete, gray or almost white and very brittle and extremely lightweight. Anyway apparently it had a halfway decent r-value. I forget now. Interesting product. But I don't think it could be poured, and it wasn't exactly structural.

I can't claim to have used or know much about styrocrete, but I thought that was a non-load bearing external application like stucco. I might be wrong about that though. I've used cement board many times. It's almost like drywall or something, but it's constructed out of cement and little styrofoam balls. That's an interesting product too. Those sheets like to snap in half though. Bit of a pain to be honest.

[Frank S]

I disagree with you there. Concrete has an atrocious r value. Poured concrete is closer thermally to steel than any kind of insulation. It's the sitting down on a cold toilet seat of building materials. Generally we pour 4" over q-deck which I think is industry standard in North America, so assuming this pour is roughly the same thickness that'll get you an r-value for that whole roof of around 0.3.

Normally around here concrete roofs are specified with 4" of iso insulation laid on top for an r-value of 25, then the water-tight roofing system is installed over top of that. One single inch of iso insulation will get you an r-value of over 6. So one inch of iso insulates as much as 75 inches of concrete.

Maybe that is why most buildings in Kuwait were made with 12 to 24" thick concrete walls no other insulation, you can cool a reasonably sized apt with a single unit mounted in a window though, Central HVAC is or was when we were there was almost unheard of except for large hotels malls or things like that. But the roofs of buildings that were not steel would have several layers of bitumen sealed and topped with 2 to 3 inches of gravel.
Sorry but North America still mostly builds stick frame tender boxes waiting for a match to light them ablaze.
When this 50 year old 1800sq ft shack we live inn either gets blown down or burned down it will be rebuilt out of concrete and steel but with 4 inches of closed cell PIR insulation in every wall and 8 inches of metal clad PIR sandwich panels for the roof. When I tore the back room down to the studs after we got this place to get rid of black mold I built it back with 3-1/2 inches of closed cell self extinguishing PIR panels in the walls 6" in the celling 2 1/2inch layers of treated OSB decking and sheet metal roof the outer cladding has 3/4inch construction board covered with Hardy cement siding 2 3ft by 6 foot double pane vinyl framed windows. It is on the East and South side of the house and is not connected to the HVAC heat pump system so we heat it in the winter by a single 1200 watt electric space heater even when the temps last year stayed below freezing for 13 days it never got below 60°f, but that may be because the room is only 200 sq ft with 7 1/2 ft ceiling on slab.
However back to the sloped roof video there is nothing to suggest that they don't have insulation under the concrete nor that they will not be sealing the surface with some substrate. My money would be for gel coat then painted with a 100% UV stable paint. or colored gunite pool coating

[silverback prime]

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.😁