Metal roofing

[traveler]

This must have been discussed before, but I came up empty on a search, so...

I have 2 roofs to do this year (or next). Couldn't me (much) simpler, both 4/12 pitch, no valleys at all. Garage is 30x40 and the house is 28x46 (I think).

Pole barn next to the garage is metal roofed, of course.

I really don't want to do shingles, getting old I guess, or lazy. Or both. Looks like with the metal I could go right over the old shingles, possibly with some furring strips.

So who's done this? General cost comparison? Installation issues?

If this went well, I'd probably do it at the cabin at some point too. Same very basic roof there.

[PurpleFloyd]

We did my Mother In Laws roof like you are thinking about 10 years ago. The lumber yard told us that rolling heavy roofing paper over the shingles would be good enough to protect the steel from the grit on the shingles so that is the route we went with. The installation was simple and straight forward and with the brother in law we got the steel and new gutters installed in a weekend. Not sure of the cost but if and when our rambler needs a new roof it will be getting steel.

[Archtek]

Before I retired from architecture, we designed many metal roofs on commercial buildings. We would not consider doing a metal roof without the whole roof covered with the high temperature ice & water. That's even using the concealed fastener systems. The problem with the exposed fastener systems (I assume that's what you're using) is that over time the UV makes the rubber washers on the fasteners harden and crack, leaving the roof prone to leaks. I would suggest you research the specific panel system you want to use and follow the manufacturer's recommendations. That was always our first step whenever we designed a roof system, or any building system for that matter.

[traveler]

thanks for the input PF. Archtek; this is my first step in my research...I'm hoping I get a lead or 2 on systems others have used. I spent a 1/2 day reading some mfg sites and as usual, left more confused than when I started!

ok, not really...but there are a lot of choices, and as my job is about as simple a roof as you can get I'm hoping to find the easiest, most cost effective route.

[crothmeier]

We Strip over ONE layer of shingles with a 1x4 or 2x4 every 24" on center, making sure to screw or nail through the shingles/sheathing into the rafters. then apply the steel over that. remove and cut back the ridge shingles for attic ventilation and cover with a Ridge/Uni-vent closure.

I typically sell the narrower ridge cap, and Residential Style Eave and Gable trims to make it look less "pole-barny"

Definitely saves money not having to tear off and dispose of the existing shingles. It also leaves a secondary layer of protection if you happen to have a leak down the line.

The manufacturer we use labels this as an acceptable way to install their steel so long as there isn't more than one layer of shingles on the house.

[CAMAN]

From what I have heard, if you place steel roofing over old shingles the shingles may transfer their shape through the steel and be very noticable. I would rather spend the little extra time and tear down to the sheathing. Doing so will also allow you to inspect the sheathing to make sure there are no bad spots. You will also need to cover the sheathing with 30lb felt.

Also you do not want furring strips, you need support under the entire sheet otherwise they will be damaged easier.

[Dave]

Newly built cabin about 9 years ago and love it. Snow slides right off. I hired it out and it took not quite a day. Some of the screws do pop up, however, and I need to go up and screw them back down.

[crothmeier]

Most Every steel manufacturer recommends furring strips, or "purlins" for installation. Typically no more than 24" on center for a roof. Supporting the entire piece of steel would be a vast waste of money if building new. The steel is designed with certain tensile strength that allows for such an installation. You already have the sheathing there so its down to the cost difference of removing and disposing shingles versus purlins over the top and felt.

Synthetic felt under steel works much better than the asphalt 30# felt, as that can heat up and bleed out much like regular ice and water does.

Going over the shingles will not transfer through the steel. If you have a dip/sag in your roof that might, but can easily be straightened using purlins. This method is listed in the recommended installation methods provided by my main steel supplier.

[fivebucks]

When you get to installing them a nice product to help eliminate bat dens can be bought at a lot of roofing supply places. Basically black foam with tape attached to flat end and opposite end is in the shape of the steel roof. Bats seem to like the small 1" ridges on steel roofing.

[crothmeier]

^^^Closure Strips

[53orbigger]

We have had a steel roof on the cabin for about 10 years now. The only complaint I have is what others have mentioned about the screws coming loose leading to leaks. Every summer I have to climb up on the roof and tighten every screw on the side of the cabin that gets the most direct sunlight.

[Bearfan1963]

I did my garage 4 years ago, 30# felt over the shingles, no issues cost about 1200 doing it my self. First time I did it and was really not that difficult. Doing my mobile home this summer with the same thing and just ordered material. It is 78x16, cost for material 1400 and then about 75 bucks for delivery. If the place is heated during the winter, you may need to something better than felt because of moisture build up under metal. Adds about 1000 to the cost, but better safe than sorry. Mine is a summer place, so it is not heated in the winter.