Is it possible to build a roof without organic material and without flammable material (felt roofing)? It will be for a garage and should be insulated to remain frost-free during the winter.
I am going to build a garage that will connect our house with our neighbor's garage. The structure will be a stone construction. Besides the necessary fire protection, it would feel good if it completely lacked materials that can burn. Both to protect the houses from fire arising in the new garage, but also to delay the spread of fire from the neighbor's garage to our house via the new garage roof.
Wood beams can of course be replaced with steel beams, but can you lay a metal roof without sheathing, and can you get good insulation with steel beams? What would such a construction look like? The slope of the metal roof will be perpendicular to the roof beams.
(Can you frame at 600 with square tubes and lay aerated concrete blocks on top? 75x200x600 mm weighs about 5 kg )
Sheet metal roofs without sheathing work fine, but you still need a membrane underneath, but plastic won't mold so you're good there. Having steel instead of wood as rafters gives a slightly worse U-value but not a significant difference. You can insulate more to counteract that. And mineral wool is non-combustible.
Sheet metal roofing without sheathing is possible, but you still need a membrane underneath. However, plastic won't mold, so you're good there. Having steel instead of wood as the truss material means a slightly worse U-value, but not significantly so. You can add more insulation to counteract this. Rock wool is non-combustible.
How closely do I need to space the beams? It feels like standing seam has less load-bearing capacity than corrugated, but with corrugated metal you screw through the roofing, which doesn't seem ideal either.
You could indeed lay fiber cement panels on steel ridges without an underlayment. With sufficient roof pitch, it should be reasonably tight. Metal roofing requires some form of condensation protection, which is probably flammable.
How close must I space the beams? It feels like standing seam metal has a bit less load-bearing capacity than corrugated, but with corrugated metal you screw through the roofing sheet, which also doesn't feel so good.
Either you choose self-supporting TRP-metal or you go with corrugated metal, but then you'll need steel battens if you're so concerned about fire. Standing seam metal is out of the question as it requires an underlying material like tongue and groove boards.
When it comes to fire protection, it is not certain that it will be that good anyway. The risk is rather that hot fire gases are retained under the roof and can be led to the next property. It is far from only whether the building itself can burn that determines how flammable it is. There are probably better things to do than replacing all materials with non-combustible ones.
I'm not saying it's a fixation, just an idea I wanted to check out. And maybe it wasn't a good idea, but you never know in advance.
I've had a designer take a look and he had some ideas. He mostly talked about fire protection inside the garage and said that if our house (and the neighbor's garage) were built today, they would be built according to different fire protection regulations. I thought I might be able to compensate a little for that...
With double plasterboard, you're pretty safe anyway.
Another thing to consider is how a potential fire would start and grow. How are flammable chemicals stored, etc.?
I am mostly afraid of a fire in the neighbor's house (or garage, both wood structures) spreading to our house. I want to ensure that it takes as long as possible. So the roof covering and joists are more significant, I would think.
Yes, my house has a stone structure, and so does my garage as I wrote in the first post.
A fire would most likely spread over the roofs, as the garages are only one story while the houses are two-story. If the neighbor's wooden garage catches fire, the fire will spread over the roof of my garage.
When it comes to fire protection, it's not certain that it will be that good anyway. The risk is rather that hot fire gases are retained under the roof and can be led to the next property. It's far from only whether the building itself can burn that determines how flammable it is. There are probably better things to do than to replace all materials with non-combustible ones.
@Daniel 109 is clearly onto something important here. "Flashover" is what it's called when the fire spreads from A to B solely with the help of heat. A garage made of stone and metal neither makes nor breaks the situation; in the worst case, it functions as a blowtorch if the heat is conducted through the structure to the next house, e.g., by draft.
We haven't even touched on the fact that a garage by its nature often contains highly flammable items. Your well-fueled car, for example, and when it explodes from the heat in the neighbor's fire-ravaged home, no metal roofs in the world will help...
If you're worried about your combustible neighbor (what is he doing anyway?!), you might rather diplomatically ask him if you shouldn't invest in a joint alarm and fire warning system. Quick extinguishing is always the best when the fire is rampant.
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Andreas Lundgren said:
