lzerarc
Basic Member
Posts:423
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| 09 Nov 2010 11:53 AM |
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I have been playing around with the ribbed metal roof, but pricing is pretty high over shingles obviously. I was driving by a new building being constructed, and it has wood trusses with 2x4 horizontal purlins looks to be about 2' oc spacing on the trusses. They then installed the metal directly to that. I am assuming they will then blow in cellulose in the trusses.
I have tried searching over the web for the last few days and talking with other collegues. Has anyone done a house this way before? I can see it as a cost and big time saver with not having to install all of the osb and then roofing paper. (plus the pull out issues of the screws in osb).
What are some of your thoughts on this type of construction vs either metal ribbed panels on osb or a standard osb/shingled roof? |
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bp f150
New Member
Posts:29
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| 09 Nov 2010 11:59 AM |
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I have only done a few steel roofs in the past. We did use the approach you described. However we use 1 x 3 material instead a 2 x material. We have never got called back and the system is very solid and there is no guess work when screwing in the sheet metal. It is good pratice to install the screws where the boards cross over the trusses.
I however have no clue if there is something problematic in accordance to code with what I described.
Good luck in your project. |
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Farmboy
Basic Member
Posts:356
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| 09 Nov 2010 10:16 PM |
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You might check out the installation installation/details here http://www.fabral.com/technical.php#install. Whether to use a solid deck depends on the application, i.e., residential, commercial, agricultural, etc. Also pull out force depends on your design wind speed and can be improved by increasing the diameter of the screws. There's a table in the installation guide.
Fabral makes metal roofing used by many installers and I followed their instructions when I built a small outbuilding using OSB decking for the roof. I believe they recommend solid decking for residential use.
A pole builing installer had previously constructed a 30x45 building for me using trusses and purlins. I had roof leaks at several locations where ring shank NAILS had been improperly installed. Luckily the underside of the roof had been sprayed with Icynene foam, an open-cell insulation, which allowed the water to percolate directly down so we could pinpoint the leaks. Most are fixed now.
There are many testimonials about metal roofs and their benefits. But like most construction products, the key to success is proper installation. Dave |
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wes
Advanced Member
Posts:810
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| 10 Nov 2010 07:38 AM |
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The actual installation of metal roofs on 1x or 2x purlins has been done for decades on ag and wood framed commerical buildings. Its use on residential projects is far less common, but has been done a lot, especially in rural areas. The use of purlins vs. solid underlayment is really dependant on the type of metal you choose. Most through fastened metals are strong enough to span the purlins without deflection or loading problems. Most concealed fastener systems tend to be flatter between the ribs, and therefore will 'telegraph' the deflection between the purlins, needing a solid underlayment to remain smooth. Your metal mfg. can supply specifics about each style of metal they offer.
Another thought, if you plan to spray foam insulation onto the underside of a metal roof on purlins, install some type of underlayment (Tyvek, etc.) over the purlins before applying the metal. The insulation then attaches to the underlayment, and should you ever have to remove a piece of metal, for whatever reason, you do not destroy the insulation in the process.
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| Wes Shelby<br>Design Systems Group<br>Murray KY<br>[email protected] |
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wes
Advanced Member
Posts:810
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| 10 Nov 2010 07:43 AM |
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Damn double clicks. |
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| Wes Shelby<br>Design Systems Group<br>Murray KY<br>[email protected] |
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lzerarc
Basic Member
Posts:423
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| 10 Nov 2010 09:19 AM |
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thanks for the replies. The system would most likely be a ribbed system, not a standing seam. However looking through details many provide for residential use, it appears they are putting osb and felt under it. I really like the look of them and their benefits, however the wife still likes shingles. Not using osb would be some cost savings (and a lot of work savings) to help offset the added cost of metal vs fiberglass shingles. If osb is required, I will probably stick to installing shingles. |
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ICFconstruction
Veteran Member
Posts:1324
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| 10 Nov 2010 11:13 AM |
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I am doing an exsposed fastener metal roof on my own place. The difference in strength for wind and snow load are my concerns on whether to use purlins or sheathing, versus cost.
But I am convinced, after inspecting thousands of asphalt shingled roofs, metal is the way to go. |
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| Brad Kvanbek - ICFconstruction.net |
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lzerarc
Basic Member
Posts:423
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| 10 Nov 2010 12:03 PM |
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ICF- you are in MN, I am in northern IA so we have similar snow and wind loads. What have you deterimined for purplins vs sheathing? I would still have my trusses 2' oc, then the purlins would be 2' oc horizontally.
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ICFconstruction
Veteran Member
Posts:1324
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| 10 Nov 2010 12:35 PM |
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We know purlins would be cheaper, but I have not broken it down. I am no engineer, but I would think pulins versus sheathing would make no difference for live load (snow). required design for snow load was recently lowered to 35psf here in the metro of MN. Although I had my trusses designed for 42psf, the old requirement. Sheathing should provide a much more rigid roof structure and therefore withstand greater forces of wind.
But I too was hoping to get some suggestions on the question. |
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| Brad Kvanbek - ICFconstruction.net |
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lzerarc
Basic Member
Posts:423
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| 10 Nov 2010 02:00 PM |
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I just pulled open the 2006 RBC to see what it says about metal roof requirements. It states it is required to be installed over solid or spaced sheathing, unless the panel is specifically designed to be applied to spaced supports. It also does not mention a requirement for underlayment as it does with the other materials in the code book. I guess all this tells me is it might be ok by code at least....
I pulled up my roofing quote for materials. my shingles cost about 3113, and osb is 1080. Felt and ice and water is 415, so that totals 4608. Metal roofing is about 135/sq, so that makes it around 4700, plus a few hundred for the purlins. |
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ICFconstruction
Veteran Member
Posts:1324
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| 10 Nov 2010 07:08 PM |
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I see better shingles cost $70 sq and middle grade exposed fastener steel (lifetime warranty) $100 sq.
The 2006 IRC, that Minnesota uses, says that metal roofing can be installed with solid or spaced sheathing per the manufacturer. |
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| Brad Kvanbek - ICFconstruction.net |
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Pushpak
New Member
Posts:1
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| 20 Sep 2019 08:59 AM |
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As this has happened, many metal roof systems have been developed which must be installed over solid decking as that has been the construction trend anyway. (It should be noted also that some metal roof systems have designs which require that they must be secured to battens, not solid decking. |
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Steel Fabrication
New Member
Posts:1
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| 07 Oct 2019 06:46 AM |
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As you know, Metal is a popular building material because it is easy to install and so metal roofing is important. It is the perfect option for storm situations.
https://www.indiapropertyclinic.com/services/steel-fabrication |
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