Murph Posted September 30, 2008 Share Posted September 30, 2008 Any steel building contractors here? I did some steel building work in Lousiana in the early 90's, and then here in Illinois. The problem of condensation is my concern. I'm considering doing a steel roof over on my 100+ year old home here in Illinois. It has 2 roofs (shingle) on it now. Do you think it would "sweat" with those two asphalt shingle roofs under it, or would I be okay? You see em' everyday, but my hunting cabin in the woods does "sweat" a little. Thanks in advance. Murph. :D/ Link to comment Share on other sites More sharing options...
MikeRom Posted October 1, 2008 Share Posted October 1, 2008 Boy, I thougth this was going to be a COMPLETELY DIFFERENT conversation :) Link to comment Share on other sites More sharing options...
Murph Posted October 1, 2008 Author Share Posted October 1, 2008 Ha! Yea, I knew it would get some hits........ Murph. Link to comment Share on other sites More sharing options...
L5Larry Posted October 1, 2008 Share Posted October 1, 2008 Now this is an interesting post on a Guitar manufacturers website. I was in the industrial contracting business in the 70' & 80's, and my company now does residential design/construction/restoration. I was always of the opinion the underside of metal roofing needed air to breath, but then we started using "blanket" insulation for certain installations, layed down and sandwiched right between the purlins and the corrugated sheeting. The last residential corrugated metal roof I did (new construction) was framed in a standard manner, plywood decking on wood trusses, covered in felt paper (just like as if you were going to put on asphalt shigles). The corrugated metal sheeting was then layed right on top of the felt paper and screwed down to the plywood decking. This was all per the roofing manufacturers specifications. The manufacturer of your metal roofing will be able to advise you best based on your specific application. If it were my cabin, I would look at two installation options. Strip the roof clean down to the deck, and install new felt and metal roofing per above, Or nail 2x4's, horizontally, layed flat, right over the existing shingles and fasten the metal roofing to these "purlins". For light guage corrugated metal roofing, these purlins usually need to be in courses about 24" apart. This gives you a good straight and level surface (hopefully) to screw you metal to, plus gives you a 1 1/2" airspace. The first method takes more labor, felt paper and dump fees to strip and dispose of the old shingles and install the new felt. The second method costs you more in lumber. Link to comment Share on other sites More sharing options...
Murph Posted October 2, 2008 Author Share Posted October 2, 2008 Yea Larry, the jobs I did in the 80' and early 90's used insulation layed on the purlins, not very thick, but in plastic which I assumed was also a vapor barrier. My idea was to just lay the sheets on the 2 layers of shingles and screw into the decking. This old house has 3/4 inch wood decking, not plywood, it's like 1 x 6 's. No stripping, no haul off. I don't think there would be much condensation because there wouldn't be a big temp difference in the top of the sheet, versus the bottom of the sheet. Thanks. Murph. Link to comment Share on other sites More sharing options...
callen3615 Posted October 2, 2008 Share Posted October 2, 2008 .....um you subject line is slightly misleading. Link to comment Share on other sites More sharing options...
L5Larry Posted October 3, 2008 Share Posted October 3, 2008 My idea was to just lay the sheets on the 2 layers of shingles and screw into the decking. This old house has 3/4 inch wood decking' date=' not plywood, it's like 1 x 6 's. No stripping, no haul off. IMurph.[/quote'] Screwing into the 1x decking would be fine, the problem is getting it look like anything. Screwing (or nailing) down through two layes of old shingles will cause a lot of waves in the sheeting due to the inconsistancies of where the fastener hit the shingle laps and how much the shingles compress when getting the rubber washers on the screws to seal properly. You should have no problem getting a weather tight installation this way, but I'm afraid it would look like crap. Stripping the roof out in 2x4 purlins layed flat would eliminate this possibility. In the 70's & 80's I was doing work for companies like U.S. Steel, Proctor & Gamble, Monsanto, and ADM, and although the clients did not know the technical details of the roofing and siding systems, They were very concerned that it "looked' good. By laying the flat 2x4"s you creat a straight, level, and rigid plain to fasten to. Link to comment Share on other sites More sharing options...
Flight959 Posted October 3, 2008 Share Posted October 3, 2008 .....um you subject line is slightly misleading. Indeed! Get's the visitors in though... Flight959 Link to comment Share on other sites More sharing options...
ChanMan Posted October 3, 2008 Share Posted October 3, 2008 I'm pretty sure there was pic of an erection specialist in the Pic of the Year thread..... Link to comment Share on other sites More sharing options...
Murph Posted October 3, 2008 Author Share Posted October 3, 2008 In all seriousness, the trade "is" called metal building erection. A play on words to get some hits. Best of luck. Murph. Link to comment Share on other sites More sharing options...
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