Hi folks,
I’m constructing a building for my aux. generator as I’ve previously discussed here. I’ve laid up the CMU walls and am now at the point for the roof. Am considering using some welded steel for the trussframe structure but not sure what to use as sheathing? Reason being I want it fireproof.
I know they make flame retardant plywood but any other good options? I thought of a metal roof but wouldn’t that require some means of sheathing underneath? Span is not a big problem as the building dimensions are only 6′ x 6′.
As always, any thoughts or ideas are appreciated!
Mike
Replies
You are better off with solid lumber( not truss) framing and steel roof. Skin the cieling inside with type X 5/8" guyprock and tape the seams.
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Would you need sheathing? I thought there were clips or something you could use to attach metal roofing, or at least that corrugated decking material, to the steel trusses. You could make a sort of sandwich with drywall, then plywood, then either metal or cementitious shingles.
piffin is right. but if your hell bent on steel know that structural steel should be protected from the heat. just because its not combustible doesnt always make it a good fire barrier. there is a spray foam type product ive seen installed on structural steel to keep the heat off of it.
if you did have steel exposed to fire and it witheld, the inspector would test it for hardness. if it hardens or weakens you would have to replace it anyway.
Thanks guys. Keep in mind however I did say 6 feet by 6 feet so the aspect of protecting the steel is not really an issue as its just an out building. My main goal is just to prevent and accidential fires on the generator from igniting the roof framing...hence my intention of using steel as opposed to any wood.
I had considered the 5/8" Type X like Piffin said and just wrapping the whole roof understructure in it. Then I could use solid lumber framing and regular plywood sheathing. I just thought this would be more work than say something which is not flammable...like say steel sheathing on a battleship ;)
Mike
If you had a fire in a gen shed, it would be a liquid fuels fire, even if it started as an electrical fire. That means flame would fine a way to vent and torch out through seams in and at edges of a steel roof, so you would still need to protect it with type X or a spray on seal coat anyway to stop the flame spread and air flow as well as to protect the steel itself.Since your goal is to protect adjacent buildings from spread, I stand with first recommendation.
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Piffin,
Got ya. Following along that line...Do you then think it might be wise to install a ceiling of Type X (maybe even two layers to make a 90 minute barrier) on metal furring channel as a barrier to the roof structure as that would be even easier to build than wrapping all the undersides of the framing members?
That would actually be very easy to do and yet still have a normal frame roof structure, sheathing, etc.
Mike
Concrete, cast in place.
Hmmm? Didn't think of that. A 6' x 6' slab however might require some engineering to make the span? I'm thinking it would have to be about 6" thick? I'm not a P.E. however so thats just my guess?
Mike-
What about another concrete idea?
Look at precast concrete planks, span would be no problem and they may even help you size the plank for that span. Check out these companies: Spancrete of Fabcon.
I also am not an engineer, so please don't consider this as engineering advice. :) If I were building one for myself, I would feel pretty confident about a 4" slab with a #3 rebar around the perimeter about 1-1/2" or 2" in from the edge and a grid of #3 rebar on 6" centers.
it is not the thickness, it's the steel.Wrap frame members? just screw the rock to the bottom edges
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