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don62
Member
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# Posted: 15 Jan 2017 07:47pm
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I have an old resort cabin built in the 40s, it has a shingle roof, I want to put a metal roof on it. This is only a seasonal cabin, should I strip the shingles[1 layer] or put the metal over the old roof?
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Atlincabin
Member
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# Posted: 15 Jan 2017 07:53pm
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I would strip the old shingles.
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darz5150
Member
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# Posted: 15 Jan 2017 08:01pm - Edited by: darz5150
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Check the metal companies warranty. I just replaced an old roof. No warranty if layed on shingles. But they will warranty if felt paper is installed between shingles and new metal.
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DaveBell
Moderator
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# Posted: 15 Jan 2017 08:11pm
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You won't get a flat enough surface and the special grommet screws may not be long enough. Strip the shingles.
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don62
Member
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# Posted: 15 Jan 2017 08:41pm
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Sounds like I'll strip the roof.. Then do I just use felt paper on the wood and the steel over that??
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bldginsp
Member
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# Posted: 15 Jan 2017 10:02pm
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Yes, but be careful to replace any rotted wood underneath. Shingles are frequently put down on skip sheathing, which is 1x6 or 1x4 boards spaced 4-5 inches apart. Usually some of the skip sheath is rotted. If rafters are rotted now is the time to replace them, hard as it is. Then, if there isn't already, you can put a layer of plywood or OSB over the skip sheathing. This will give a uniform surface to work with, otherwise you have to be sure the screws hit the skip sheath. Plywood or OSB will also strengthen the roof substantially. Note that there are two basic types of metal roofing- standing seam (no exposed fasteners) and R-panel, where the fasteners are exposed. Exposed fasteners will eventually loosen and leak, but standing seam is more expensive and harder to install. Good luck. Roofing is not for the shy.
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Shadyacres
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# Posted: 16 Jan 2017 12:42am
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If not too many shingles and fairly uniform you can also get some rough cut 1 X 4s and screw them to your joists and than put your metal roof on. I would use screws for both 1 x 4s and roofing.
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neckless
Member
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# Posted: 16 Jan 2017 07:40am
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it is a cabin.... i vote for shadyacers reply....screws will wick moister through the screws , so something is needed under tin...
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toyota_mdt_tech
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# Posted: 16 Jan 2017 08:51am
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Don, this is what I would do. Strip it, lay down a water proof membrane under it. Mine had felt paper, I have an uninsulated attic, so my screws dont sweat and a dry climate also helps.
But a good HD upgrade would be the water proof membrane underlayment under the metal roof. Use long enough screws. Keep all screws in perfect alignment both horizontally and vertically, or it will stand out like a sore thumb.
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old243
Member
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# Posted: 16 Jan 2017 09:14am
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If there is a chance of ice buildup at the eave and damming water up. I would suggest using at least one row of ice and water shield , the first row at the eave. Also any valleys Then tarpaper the rest of the roof. I have replaced the roof on my house, I used ice and water shield and have had no problems since. old243
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KinAlberta
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# Posted: 16 Jan 2017 07:34pm - Edited by: KinAlberta
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The guys that we hired said just go over the shingles. It just seemed wrong to me so I googled and googled - and googled it.
Surprising to me was the number of people with direct experience, either doing it or owning it, that approved of metal over old shingles. So, that's how we went. The screws go through the tar of the asphalt so I guess the seal is pretty good. Longer screws were used
No one really says this but my guess is that the old underlying shingles shed water pretty well if there is a leak around a screw plus they would spread out support much more finely than would strapping the roof, unless lots of closely spaced strapping is used.
I was worried about lift but the steel's ribs and the number of screws used just locks down the sheets.
Our underlying 1950s plywood roof was good per comments made about 15 yrs ago when it was last shingled with asphalt.
We also have a couple boathouses (one is about 16x22') with standing seam steel roofs. They are done over the rafters with no sheathing at all under them and are very solid to walk on. So higher quality steel, much stronger gauge can make a huge difference in some applications.
Just start Googling...
"In over 30 years and tens of thousands of installations over old shingles, I have yet to go back on a job later and find myself saying “Hmmmm … maybe the old shingles should have been removed.†It just never becomes an issue. And many of those installations actually have been over wood shingles and thinner wood shakes! I have also re-roofed personal properties with our products five times now over the years — every time was over the old shingles, and no regrets.
I like going over the old shingles for three reasons:..."
- See more at: http://www.asktoddmiller.com/history/should-existing-asphalt-shingles-be-removed-befo re-a-metal-roof-is-installed/#sthash.nPXOsgt7.dpuf
http://www.asktoddmiller.com/history/should-existing-asphalt-shingles-be-removed-befo re-a-metal-roof-is-installed/
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Shadyacres
Member
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# Posted: 16 Jan 2017 07:52pm
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I'm sure it will do fine , the reason I said to use purlins was to get a more level surface and better bonding with the screws as you can screw the purlins directly into the joists. I always put my purlins about 18 - 20 inches apart or closer. Also I like the purlins because you get some venting between the shingles and the new metal roof.
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creeky
Member
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# Posted: 16 Jan 2017 08:40pm
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There's lots that do the "leave the shingles" here.
One advantage to removing the shingles I could see tho, would be if yer re-strapping anyway. You could put down a 1" layer of polyiso and do a cool roof.
Keeps the heat out during the summer.
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don62
Member
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# Posted: 16 Jan 2017 11:10pm
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KinAlberta.. Great reading, thanks everyone for the replys...One reason I would like to leave the shingles on is noise insulation, rain on a tin roof is loud.
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toyota_mdt_tech
Member
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# Posted: 17 Jan 2017 08:25pm
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Quoting: don62 One reason I would like to leave the shingles on is noise insulation, rain on a tin roof is loud.
Will you have an attic? I ask because I cant hear the rain on my roof at all and have been there during a monsoon downpour. But I do have an attic too. I like the sound of rain actually. I was disappointment when I could hear nothing.
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KinAlberta
Member
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# Posted: 17 Jan 2017 08:37pm - Edited by: KinAlberta
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That's a great point. Depending on the people and the place, it could become a really irritating issue. I have a noisy furnace that I can't wait to wear out and for it to be gone.
Stripping the shingles might open up better noise reduction options.
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don62
Member
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# Posted: 18 Jan 2017 01:44am
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Its a strange situation, I actually have two roofs. The original cabin was a 1 room resort cabin built in the 40s, then a long time ago a bedroom and bathroom was added on the back and a room was added on the front, the original roof was left in place and a new roof was built over the whole structure..so when I took out my living room ceiling, the original room, I have a vaulted ceiling from the original roof,,, I hope that makes sense.
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don62
Member
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# Posted: 18 Jan 2017 01:55am
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I don't have good pics of the original roof but this is the underside.
DSCN9743.JPG
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DSCN9744.JPG
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DSCN9836.JPG
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donbell
Member
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# Posted: 31 Jan 2017 11:37pm
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It is better to strip the shingles.If felt paper is there, then it may tear it off easily.So it may lead to rain damage.And see that you install the metal roof as early as possible.Metal roofs are always reliable and durable.
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Jim in NB
Member
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# Posted: 3 Feb 2017 06:04am
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Nice ceiling! I hope you are thinking about screw length and the screws from the roof coming thru that ceiling - it will not look as good if they do. You may want to consider some strapping- whether you decide to strip the shingles or not. I would not strip them myself as long as there was only one layer.
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Nicholas666
Member
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# Posted: 29 Nov 2017 10:58am
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I guess, it's better to strip the old shingles and then install metal roof. Personally I'm going to do this way. Though I haven't bought all necessary materials yet, I've found out here how much it will cost me. As for the noise insulation, to be honest, I don't know whether I should worry about it or not. But it's better to think about it before I start the roof replacement. Thanks for the idea!
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dmanley
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# Posted: 29 Nov 2017 05:23pm
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I agree with Shadyacres. We had metal roofing put on our house a few years ago and they screwed purlins into the joist and then screwed the metal roofing onto the purlins. One thing they did was to cut away the shingles around the outside edges of the roof and screwed the purlins directly to the underlayment. Makes for a better look around the edges.
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toyota_mdt_tech
Member
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# Posted: 30 Nov 2017 10:13pm
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Strip old roofing to wood, repair/replace any damaged wood, then lay on 50# felt and screw metal down to the 1/2" plywood substrate. Get the long screws. Install it just like the mfg recommends.
Fascia flashing first, roof panels, then gable flashing, then ridge cap. Ridge cap is held in place with stitch screws, fascia is held in with flat pancake screws. Rest is all done with the colored gasketed roofing screws.
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