Yes or no --- putting a metal roof over one layer shingles

ryseryse_2004September 28, 2013

We are getting estimates now and I wonder what the reasons are for a tear- off if the roof isn't leaking? Is it just to inflate the estimate? We want to put a metal roof on a 2 1/2 car garage and the estimates are coming in very high.

The existing roof is only 8 years old but the shingles are starting to buckle. I think they were the least expensive shingles available. (One estimate claimed there were two layers of shingles so we would have to pay for two tear-offs. Not true.)

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Sophie Wheeler

You've got to do a tearoff. Especially if the shingles are buckled. Metal has to go over a flat surface. And you've got to inspect the sheathing. Get your ladder and shingle shovel out and you can do the tearoff. Putting the metal down isn't that hard either. We did it on our barn.

    Bookmark   September 28, 2013 at 5:20PM
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Thanks Holly. We are in our 70's now. We used to do everything ourselves but the garage has a cedar home built over it (which my husband built) and the drop on one side from the roof is over 40 feet. I'm not going to let him do the work this time.

    Bookmark   September 28, 2013 at 5:34PM
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There is not " a single "correct " way of doing a metal roof but here are a few thoughts for your consideration. I am taking you at your word about being familiar with construction because much depends on your ability to apply experience to which way to go. Be certain the one saying two layers is honest as well as experienced before sighning a contract with him. Most properly installed composition shingles look like 2 layers at drip edge because of starter strips.
Can you install metal over one layer of composition? Maybe. The main consideration is wherther the deck and frame will support the extra weight. Then there is the question of how smooth and level surface the shingles afford. Regardless of other underlying material,decking must be capiable of holding screws. 1x deck is strong but usually has many gaps between edges and ends of boards that if a screew gos through,a leak is likly. OSB and plywood are flat and smooth but must be thick enough to prevent flex between rafters.
I have installed metal over a few compostions with no problem after several years. On a couple where shingles were aged and deck was strong, we layed tar paper between the shingles and metal. Another had heavy truss framing with questionable decking so we installed 2x4 laths over tar paper making certain to hit rafters with lath fasteners.
If your husband is a healthy 70 yo,you might consider hireing laborers to work under his supervision. I agree with Hollysprings about metal not being difficult compared to other construction tasks. A word of warning about roof tearoff. Think twice about putting old shingles in anything without dump. The shingles interlace and make the intire load act as a single blob that resists shoveling off. If you use a non-dumping truck or trailer, lay a cross tie or similar on floor at front with heavy chain on it. If bed is more than 8 feet long, put another drag half way to back and leave enough chain slack between the drags to alow first to move a few feet and pull some material off before chain tightens on other drag. In farm and ranch country you may find people who have installed metal as part of thier farm work. A farmer or rancher who has built thier own barns might welcome extra or off season work. If that sounds interesting,in addition to other means of asking,check out the people on "Yesterday's tractor forums". The board you want is "tractor talk" . If you go with diy ,you can buy or rent the specialized cutters. If your husband decides to supervise labor and isn't comfortable on a ladder and/or walking on the roof,rent a lift to alow him safly going to roof level as well as saving time lifting materials.

    Bookmark   September 28, 2013 at 10:56PM
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We had a metal roof (steel shingles) installed 2 years ago and we had them remove the original layer of asphalt shingles that were about 15 years old. They were buckling bad and we were afraid any heat buildup in between would further the problem and create an issue with the new steel shingles. Plus I felt the added weight was an issue.

Check to learn about the metal roof warranty if you place it over old shingles.

The steel shingles we installed were nearly double the cost of an asphalt roof shingle; however we felt it was worth the cost since we're in a high wind and hail area. It was definitely worth the added cost for us. Many in our area are going to the steel shingle.

    Bookmark   October 1, 2013 at 9:03PM
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Check with your Fire Marshall.


    Bookmark   November 4, 2013 at 9:38PM
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When I checked into the metal roofing all of the installers told me they leave the singles in place and put 1X6 treated lumber across them to attach the metal to. Not sure if that is the correct way or not but I couldn't afford it at nearly double the price of quality shingles.

    Bookmark   November 17, 2013 at 5:15AM
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Having done installations on a primary roof instead of a tear down, I have never repeated this mistake.
I have replaced roofs three times in three different states using asphalt and cement tiles. I looked at metal tile on the last home but we lived in a high end neighborhood and it would have not meshed.

Our present home was owned by a couple who were in their 80's. They left me a packet of their repair costs. I can see that were taken several times by a few . Prices were inflated and workmanship was poor.
Some contractors assume homeowners are.... gullible.
Shop around for more quotes. Measure the work area and price out how much the material cost should be.

I have measured 800 and told I need 1200.
I recently did a basement insualtion install and measured 710. I was told I had 1200 for a three day install.
I hired the company who said I had 750 sqft and it was a two hour installation.

Good Luck
Be informed

    Bookmark   November 18, 2013 at 1:29PM
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I want to thank you all for your responses. We priced the metal supplies with asphalt and at Menards, the price in materials was only $200 more for metal. That surprised me since all of our estimates were coming in twice the amount for metal.

We had even put out an add where we would pay for the materials and insurance if a experienced roofer would want a side job --- no takers on that though.

But then we got a local company which is highly recommended who will do the job at an affordable price (metal over existing shingles.)

BTW, we are out in the middle of nowhere so do not have to worry about fire marshalls or crazy permits and regulations. There are definitely advantages to living in the country.

    Bookmark   November 18, 2013 at 4:04PM
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Windows on Washington

Can it be done...yes. Most metal manufactures will allow for this application with a slip layer of some sort and/or batten/purlin installation.

I prefer that we tear off all the old asphalt to help with the performance of the metal roof in this case.

    Bookmark   December 10, 2013 at 8:48AM
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Thanks for all of your advice. We had the roof put on (over the existing shingles) last week when there was a warm spell and before the snow came.

We were told since the underlay was in good shape and the shingles were not coming loose that keeping them in place would increase the insulation. Anyway -- it is done.

    Bookmark   December 10, 2013 at 10:36AM
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"BTW, we are out in the middle of nowhere so do not have to worry about fire marshalls or crazy permits and regulations. There are definitely advantages to living in the country. "

You can say that again !

"BTW, we are out in the middle of nowhere so do not have to worry about fire marshalls or crazy permits and regulations. There are definitely advantages to living in the country. "


    Bookmark   December 10, 2013 at 7:50PM
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