Can You Put a Metal Roof Over a Shingle Roof?

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Adam Mazzella and Jeff Hock help answer one of our most frequently asked questions: Can you put a metal roof over a shingle roof? Thad Barnette and Julianne Calapa also join the conversation to discuss recommendations, installation considerations, and more.

Topics covered:
►Intro 00:00
►Can you put a metal roof over a shingle roof? 0:43
►What installation considerations should you keep in mind? 3:27
►Is it recommended to put a metal roof over a shingle roof? 7:53

Have questions about metal roofing? Comment below to have them answered on camera by industry experts in future episodes of Q&A Mondays!

Please note the installation details and methods shown in this video are for reference only. Sheffield Metals recommends following their published installation details or for WTW projects following the required details issued and marked approved for that specific project.

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[dnahulvey]

When you use one by four strapping over the shingles nailed directly into each rafter, it creates a completely new deck and every screw is installed into a fresh piece of new wood. That is the only way to go. If you screw metal directly through shingles, you have no idea what you’re screwing into underneath the shingles. Strapping eliminates that issue

[turdferguson]

Of course you can. It’s standard practice. We’ve done hundreds of them. Some over 25 years ago, no problems.

[achillesunlimited]

I've personally seen a metal roof installed directly on the shingles, had been there 35 years. The bottom looked like the day they laid it down. Architectural shingles underneath as well. That roof is now 50 us years old and still brown. The color held up very well considering the age. Was likely a simple latex polyester

[brokedude]

On existing shingles..
If no leaks..
1/2 lap felt .
1/4" fan fold foam.
2" screws and metal of choice..
I have several 30+ year metal roofs with no leaks and no problems, they are exposed fastener roofs.
After the first year, a fastener inspection is always mandatory for my roofs . Just the odds that a few will land on a decking seam and work loose .
Sales men are clueless to what is going on ( most of em).

[kiethauthement]

Great points in this video but I have done over 100 of them with no issues an I do a thorough inspection of the roof beforehand

[hhattingh]

Changing a metal slate shingle roof for standing seam. Thanks to you guys i was able to ask relevant questions. Thank you

[francoislepine]

been there done that....1937 house...tore off one layer of asphalt shingles to find another one underneath, tore that one off to find the original roof material of cedar strapped (1x4s) over cedar shingles...first layer vertical, checking/adjusting for plane, second layer horizontal, creating a good airspace. Next was tar paper laid vertical with half overlap (uses more paper but makes handling the panels with no possible damage to paper way easier) I installed this 6/12 pitch roof singlehanded! The panels were 3 feet wide "M-form" predrilled on the ground to a 18 inch diamond pattern. That was 16 years ago and I couldn't be happier with the roof.

[jeffreyallen]

First, I would offer my opinion that it is always better to strip a roof before any reroof, for all the reasons stated, but especially for the ability to do a proper inspection. However I personally feel that the issues raised are generally overstated. I have never hesitated to do standing seam over one layer of resonably flat asphault shingles. You are only adding perhaps 1/3 the weight of a asphault roof so load is not an issue in most cases, and will in most cases be less if you are in snow country because the load will be released when the snow slides.I don't quite agree with the emphasis you have placed on moisture issues. The small amounts of moisture that may accumulate under a metal roof(residential anyway) will easily dissipate quickly under normal conditions. The problems arise when exccess moisture is being created in the living space and not being dealt with properly.Common issues in the northeast where I live? Wet cellars is a very common one, propably the worst in residential. Drying firewood in the house.Hot tubs.Large families(lots of showers, baths, etc.).And of course a leaking roof, due to improper installation or age. All these things get a lot worse in the winter when that excess water can become frost and accumulate to pretty significant quantities.Often you can't get rid of that kind of moisture with a vented ridge cap or gable end vents.My point is if you eliminate the cause of the excess moisture that solves the issue more easily that trying to mitigate it .In other words, fix youe cellar, vent baths propery, etc. .
I always use a slipsheet no matter what I go over. But again I think you might be overstating the issue of laying the metal panels directly over shingles. The given reason is the expasion and contracton causes abrasion to the contact service. But really, you make it not like there's theres someone under there with a belt sander! I have removed many metal roofs that were installed directly over asphault and never have encountered evidence of this issue. What is the coefficient of expansion on a 25 foot panel, maybe 1/16 of an inch spread over 25 feet. It would take a thousand years to wear through.But I personally love the new synthetic barriers; they're cheap and I always use them.
Having said all this I do not really disagree with any that you have said.Yours is the safest plan of action.I recently did a reroof that had rolled roofing/wood shakes/asphault(yes, asphaut over wood shakes)/asphault/ and the customer actually wanted to go over all that with standing seam to save what I knew was going to to an expensive strip.I simply refused and they took my advice, but that sure shows how extreme things can get sometimes. But often you can look at a job, say this is not going to be an issue in this particular situation and you can save the customer some money. Anyway, thanks for the informative video.

[scottyd]

Don't listen to them. They are high. Put down some felt paper right over your shingles. Trim all the overhang off the shingles.( I popped a chalk line and cut the overhang with a skill saw on shallow setting.) Let metal roof overhang about 2 inches. Go to town installing your metal roof. Oh yeah, be sure to use 2 inch screws. And do a watertight job with the flashing. The metal roof plus the shingles underneath add some additional insulation value to your house. Mine is 10 years with no leaks. Did it myself. FYI . I had bad leaks before I installed the metal roof.
You can do it with strips of wood but the name of this video, Is can it be done? Yes, it can be done.
P.S. I hate people that talk in circles and confuse the listener. Most people are looking for a simple Direct answers and to stay on topic. ( it ain't rocket science )

[davidcarroll]

Also the bottom of the roof deck gets scratched exposing bare metal on the bottom creating a spot to rust quicker, air gaps are also a common part of the insulating properties. Also furring allows a space for insulation to be added.

[nedcramdon]

Need to strip the entire roof, (several trips to the landfill (30 miles away)), ice shield entire roof ( very expensive), 1" strapping at recommended spacing and valley flashing. Then all the pricey metal gable and eave moldings, etc. and then the metal roofing of course. My roof deck is mint so I think I'll chance the "over the shingles" method.

[evamejiaartist]

the answer is yes, but make sure you have ventilation, such as 2X4 strapping and the barrier, such as the radiant barrier, on top of the existing decking, in this scenario the shingles. I am gonna do it.

[waterhead]

Thanks. This helped me make a decision to just do a tear down. We have 1000% humidity, monsoon, blast furnace summers here.

[philindeblanc]

The right way to do it is the same as how solar panels are applied, using a few inches of air space. This is what the advantage is. So just have large metal panels vs the small solar panels, and this basically shades your roof. Its not rocket science, just practical fact of sun vs shade and reflectivity vs conducting and radiating heat. Just make sure you make the air gap large enough to make clearing leaf build up easy. What you will also consider doing is deadening the metal from underneith. This will help make it quiet when it rains and with wind. This gives me an idea!!!

[HK-qjim]

Good info.
Novice roofer here. I didn't know...what I didn't know.
The cooling and retaining heat issue, I think, is a big one for me.
Answers my question. NOT the best Idea.👍

[thomasofone]

What if you put a sandwhich of black tar/felt paper between the exsisting shingles and new metal roof? Thanks in advance?

[brucebennett]

There is a downside to tear offs. Mostly with smaller crews, they might tear off Thursday n Friday. Rooftop delivery comes Monday with fell paper, weather shield, drip edge. If it rained over weekend the truck is still coming. Hey guys the roof is dry enough, get to work. Hey boss how is the plywood ever going to dry? When it rots we get another job out of it. I would imagine this could happen when your metal roof guys show up.

[rodbaker]

I bought a old farm house with standing seem over shingle over wood shingle. House caught on fire. Fire department showed up and had to strip most of the steel off before attacking the fire. Normally they would simple knock a hole in the roof to allow the flames to go up instead of climb the roof inside. But because the medal was over all that it just made it hard to attack. Once the medal was off and the roof was opened up then they could drop water in from the top down. But by that time the damage was done. In that region if it was a normal standing seem it would be medal over wood slats. Again if it had a house fire it would be easier to punch holes and vent the fire because there wouldn't have been near as much fuel sitting directly under the metal.

[otahu]

We live in Atlantic Canada. Damp and wet and boat loads of snow. Our camp has had Metal. Right on the shingles for Decades. We left the ends open and the cap has room for air flow. We also have solar panels on the roof and a wind mill. It's been great for 20 years. We haven't had any of the issues these people are talking about. The roof is light grey to reflect the heat. We also have a solar heater box that we use a sheet of the same color. To cover in summer. A light grey roof will reflect the heat.

[Mrsalpiness]

if a roof could be layed over with metal. it would be less waste than tear off and re roof.