Expert: Bruce E. Johnson - 10/23/2009

Question
I am wanting to build a concrete block building with a metal roof for a bunk house at our ranch where we deer hunt.  We recently had a fire that burned down several of our bunk houses and trailers.  I figured that this would be the way to go since this could happen again (we have 285 acres, but the fire burned around 4,000 acres).  I want to use as little wood as possible, but I am wondering about how to get the metal roof attached to the blocks and be secure.  I am looking to build a structure in the neighborhood of 10 X 20 with about on 8 foot ceiling.  I am wanting to use on concrete slab to build on.  Also, I can use rocks from a creek bed which wouldn't cost me anything, but I figured the concrete blocks would be more fire resistant and I wouldn't have to use wood.

Answer
Hi Roger, If you are going to use steel roof joists you install metal embed plates in the concrete bond beam at the top of the wall and weld the joists to the embed plates.  If you are using light gauge metal trusses then you install vertical straps in the concrete at the top of the wall and screw the straps to the metal truss.  This is the same procedure if you are using wood trusses, the beam strap is nailed into the truss.    If you are talking about how the roofing itself is attached to the roof structure it is done a couple of ways.  With light gauge metal trusses you screw highhats or metal stud purlins at right angles to the truss and then sheet the purlins with the metal roofing.  Wood trusses can be treated the same way, with purlins or high hats and then the roofing, or the wood trusses can be sheathed with plywood or 1x4 stripping and the roofing attached to the plywood or the stripping.  With steel joists you would sheet the joists with corrugated sheet metal welded to the joists and then screw your metal roofing to that or install a layer of polyisocyanurate foam insulation with a nail base attached to it and screw your roofing to the nail base..I hope this information helps please feel free to write again regarding this or other matters, sincerely bruce e johnson..bejohnsonconsulting.com