OT Metal Roof

Well, I've put it off long enough, this will be the year for a new roof on the house. Like to do a metal roof, anyone have the experience? I've built barns with metal roofs, but just over rafters & stringers.

Seems to me to do it right, I should probably tear off the shingles, fix any weak spots in the sheathing, put on felt then the metal. Or do I need furring strips anyway?

Or can I just put it on right over the old shingles with furring strips? Google Images shows people doing that. But it seems like the lazy way out. Of course, I'm kind of a lazy guy, so...

How did you do it? Any advice will be appreciated.

Thanks,

- jhilyer

I'd start with metal roof manufacturer's specifications, I'm sure you'll find appropriate details to help with your installation, not rocket science, but will insure your installation is correct and warrant-able by not violating the spec's. I've done a few, 1/2 of our large horse barns, as well as some state jobs with Fabral specified standing seam metal roofing. They had some interesting spec's. secondary roof under the metal was all Grace Ice & Water Shield, they liked this material because it was self healing if a fastener penetrated it. One thing they did not like and was not allowed on job site was field cutting, problem with that was the finish on the cut edges were removed, I distinctly remember those kinds of details. Between comments here and what the manufacturer of the material you plan to use, you should get a good idea of how you want to do this. On my friends house I think we furred over the existing shingles, was kind of a roof installation get together, already started. Loading for existing framing comes to mind, so if theres layers of shingles and snow loads to consider, things like that you may want to look into, in his case its been on there 11 years now, and no problems. The other is wind loading, lift forces, you have to make sure the fastening is done correctly, and will withstand those kinds of loads, usually fine if whats existing works with the fasteners called for.

What I like to do is put 2X4 layed flat with 1 1/2 inch foam in between the wood it helps with sound transfer and if you have to walk on it you will be less likely to dent it

I have put metal concealed fasterner system from Menards on my house a couple of years ago. They have a brochure on how to do it at the store and maybe their website. I have been very happy with it. It will lay better and look better in the long run to strip the old and lay it on the sheeting.

Lots of people around here putting on metal roofs with either the 3 foot exposed fastener stuff or the concealed fastener stuff.

I like the way the snow just slides off..!!

Ours was installed wit new transverse 2x4's, new Valley 2x6's and 1/4" foam sound deadener.

Hardly can hear even a down pour ..!

Baked Enamel colors look good..Guaranteed for 40 years, the old roof was 70+ (metal) and the shakes were still under that..!!

Ron.

Ron.

We put pole shed steel on our cabin roof from the start. We put OSB on the trusses (24" oc) and then roofing felt and then screwed the steel down. If I was doing it over I would use 1/2 instead of 7/16 OSB, we had a couple of screws strip out. I went with a 5/12 pitch so the snow would slide off, but it doesn't until spring and then it all comes at once. I see other people put angle across their roof 2' up from the eaves to prevent the snow from sliding.

2 years ago, we had the house and garage done
by a firm that has done barns around the area
since the 1930"s Quite costly, compared to regular
asphalt shingles, but we should have done it years
ago. There was only 1 layer of shingles on the
house, and they went over it. said it would deaden the sound. We went by the sterling reputation of the contractor.

I have had a metal roof on my house since we built it in 1995. I would never go back to shingles. Been through 75mph winds last year during the tornado and never had any damage. People around lost most of their shingles. Hail does not hurt it.
It is costly to start with, but will pay back dividends over the long run. Bob

This subject has come up before. One guy from a roofing company said that he will not put steel roofing on top of shingles because the shingles will wear holes in the steel from expansion and contraction of the steel.

Personally, I would take off the shingles and put down a self-sealing membrane then put the steel on the roof.

Neighbor put down furring strips over the shingles on his house; don't know why but he had numerous leaks that it took him 2 years to get sealed.

Furring strips over shingles work fine if done right. A story about someone who did it and was plagued with leaks means nothing about the roofing itself. Just means the person did a lousy job. The plus side of using strips over shingles is the labor avoided of stripping the roof and a little extra insulation value with the dead-air space between the new steel and the old roof. The strips ought to be 1 1/2" thick minimum (2 X 4s usually used) and checked with a chalk-line and shimmed where needed to be straight. When you've got a roof with a lot of dips and dives in it - using strips allows you to straighten it out with shims. Can't do that when going directly on the old sheathing. One downside is - having to be careful walking between the furring strips. Especially if you've got thin gauge steel and the strips are 24" apart. Not to hard to put a dent in steel if you step on it wrong.

If using directly on sheathing - you really need at least 5/8" of good solid material to grab if plywood/OSB and also must have the special screws specifically made for use with plywood. I've done a few new roofs with new 5/8" sheathing and steel. On them I used self-sealing "water and ice shield" underlayment like GAF Stormguard, Certainteed Winterguard, etc. But I'm in a high snow and ice area.

I've done a lot of steel roofs over the past 30 year. Exposed fastener type, standing seam, on furring strips and directly on sheathing. No problems or leaks with any of them but I did have to replace some screws/washers on a few old ones.

The neighbor just had one put on yesterday. They went over the shingles. They laid down Styrofoam insulation and put the steel over that.

Here's one I did in northern Michigan a few years ago. Roof was terribly sagged in several areas. I built trusses -in place in the attic best I could.
Then straightened it out the rest of the way with 2x4s and lots of shims. Nice thing about this way is I could do it all myself and not worry about rain and big leaks.

We have put metal roofs on my house and cabin, 30 pound roofing felt over shingles, screwed it down. One roof is 10 years old now, still perfect. Have watched many put furring strips down and add steel, have also seen several of those roofs not do so well. One could remove shingles, then felt and apply steel much easier. We swept and used a leaf blower to remove all loose gravel. Can not scrimp on the felt though, the 15 pound is not thick enough.

The First thing you have to do, is check with code enforcement in your area.
When I was contracting, CODE veried widely from jurisdiction to jurisdiction. Some mandated complete tare-offs and some allow you to just lay steel over shingles. It all depended on the code enforcement officer's inturpition of the law.
When I was a contractor, I encouraged a complete tare off, and an application of roof fabric, on the sub strath, followed by 2x4 sleepers haveing vertical ventilation between the fabric and the steel, allowing venting between the eves and the ridge. This method is pricy, but the best way to ensure a quality job.
Loren, the Acg.

Billys got it right, check the manufacturers websites on how to do it. You will find it says no OSB an a minimum of 5/8 ply and special screws for plywood, there short and fat as opposed to the long and thin you usually see. My self, I would remove the old shingles and put purlins down to nail the roofing to like in JDemaris pictures when reroofing and old building. By checking the websites you will also see all the other pieces available to make a good looking job. I hesitate to say professional job because the house I live in had metal roofing put on just before I bought it. I cringe every time the wind blows. That "pro " is out of business now. I used to do roofing jobs myself but at 71 my feet stay on the ground now.

We put a metal roof on our house 2 1/2 years ago. At that time it was about the same price as shingles and even the people that sold shingles said that shingles would do good to last 10 years. The roofer took ours down to the decking, rolled out tar paper and screwed it down. We went through some pretty strong winds last week when the tornadoes came through and came out OK.
You might want to check with your insurance, My insurance said that they wouldn't cover wind damage if it was stripped vs screwed directly to the decking. I don't know one way or the other about it but they said they had a lot of claims on stripped roofs. :?: :?:
I've got 2 other houses and when they need roofs I'll put metal on them too.

JD Here is what the folks in these parts say about doing it with the strips. Sun hits the roof in the days then cools off at night and you get moisture build up. That moisture rots those strips in two to four years and roof blows off. Almost all contractors have gone to pulling the shingles and going right down to the decking. Note I have no experience but do have a house that has been roofed twice in the last 20 years and have been talking about going metal.

i put pole barn steel on house roof 6 years ago, went right over the shingles. dont think it will be a problem, maybe at least put the thin styrofoam under it. we can hardley hear the rain. nice thing about the steel is it goes up fast if you dont strip the shingles. screw it down.

I put a metal roof on a farm house last fall. I really like it so far. Could have done it myself but hired an Amish crew. They were like billy goats up on the roof. This was a big two story house. The crew of three did the job in four days - I would still be working on if I had done it myself. They put rough 1" by 4" 's down which makes them a little thicker than todays 1" by 4" 's. They used 3" and 4" screws which went through the firring strips, through the shingles, through the existing sheating and into the rafter. Every screw went into a rafter. They used Dewalt impact guns. They made sure each screw was actually into a rafter. If it wasn't the screw would spin out. If it hit a rafter it would pull the impact down. If they accidently missed a rafter they would just move the screw some. Original wood shingles and one layer of asphalt shingles stayed. Cost to strip the roof would have been cost prohibitive. They prefer the rough 1" by 4" 's because it doesn't raise the metal roof so much which makes the trim look better. Contractor said in 15 years he had never seen the firring strips ripped off in a storm. What normally happened was the screws holding the tin failed - either the screw pulling out or the tin ripping out. This is a steeper roof so I think it would probably actually vent somewhat keeping everything underneath dry. Attic is vented well also. If it had been a newer or high dollor house I would probably strip everything off. Screw down the firring strips to the rafers. Put pink foam insulation in between the firring strips. Then screw the tin down. I didn't use a "fad" color either. I used a medium gray color. People had told me the most colorful colors fade first. Also, you might get tired of a color like red, purple, or green. Still like my medium gray. Covered the trim at the edge of the roof all the way around as well. Took two chimneys off and five lightening rods as well. On the two porches and garage all new flashing was tucked up under the siding. Some want to just tack the flashing with nails to the siding. Contractor raised the siding and the flashing went under. NO LEAKS!! Made the house look more modern.

Ten years ago a put metal right over 25yo shingles. no furring strips. So far so good. Neighbor had furring strips over old shingles and still good. I recommend leaving the old shingle as a further layer of protection. Beside getting rid of the old shingle could be a PIA

When I get around to it, I'm going to strip the shingles, fix any weak spots, apply water and ice preventer, use stringers and purlins.
good luck
Kenny

I have put a metal roof on my house, my wife's stuio, my shop, tractor shed, tool shed and the shed that holds my garbage cans. The oldest must be at least 25 years, and still looks new. I have watched my neighbors put on asphalt more than once over that time. I live in the rain forest in the Fraser Valley, British Columbia. And we get lots of rain and when it rains it's heavy. No problems. I suggest you buy Ziplock or Snaplock metal roofing. It has no exposed screws except on the trim work. Use their gasket flashings for any vent pipes. You can pick from several painted surfaces. My house and studio have grey paint, but I decided to go with just the galvanized finish due to the amount of rain, and lack of sunshine we get in the area. I don't know where you live, but the galvanized finish will not let any moss or sticky pollen gather on the roof. I get a slight film on the painted roof that I have to wash off, especially on the north side. Also, I prefer putting it down directly on the sheathing. It's just stronger that way.