metal directly on asphalt shingles

Don Jutton
8/6/2012
I'm planning to have a metal roof installed directly over 20 year old asphalt shingles - the house has cathedral ceilings - the contractor has suggested putting down 1/2" Styrofoam panels directly on the old standard shingles and then the metal roofing directly on top using 2 1/2 in screws - he says the added cost will be minimal and I'll get a good solid base for the metal roof (better than strapping) and there will be a bit more insulation value. I saw in an earlier post that you recommend removing the old shingles to get better insulation but he says that the labor and the disposal cost will push the price beyond my budget. Are there any flaws in the recommended approach if I leave the old shingles in place? Is the increased insulation value I'd get by removing the old shingles and putting the Styrofoam down directly likely to be enough to warrant the added cost? Would it be better just to strap over the old shingles and put on the metal roof and forget about the Styrofoam?
Dick Bus
8/6/2012
The 1/2" Styrofoam will add some value. One flaw with not removing the existing shingles is that you are not as readily able to see if there is any rot under the existing shingles. It would be a good idea to also add a new layer of underlayment over the foam since you do not know what is there now from a vador barrier standpoint.
Eric Novotny
An informed customer is the Best Customer!
8/9/2012
How many square feet is the roof? Foam is a great option and you can, if done properly, convert it into a hot/insulated roof. If the roof is currently vented, putting foam on deck will not change the winter time performance but will help with the radiant heat gain in the summer. I am a huge fan of getting rid of the asphalt as well for many of the same reasons that Dick mentioned. I am happy to go into the specifics in more detail if you so desire.
Guest User
4/4/2013
Which styrofoam brand do you recommend?
Eric Novotny
An informed customer is the Best Customer!
4/4/2013
EPS (Styrofoam is a trademarked name for EPS) is not usually recommended for roof applications. XPS and Polyiso are the two rigid foams that are most often used in roofing applications.
Guest User
1/27/2014
I have a house with a 4/12 pitch, reroofed with asphalt about 10 years ago. I happen to like the look of standing seam. I have one skylight in roof. Have soffit and ridge vent. Also have a mushroom power attic fan on roof. The sheething is 1/2", which is kind of springy. Could I have another layer of sheeting added over the exiting shingles or do they need to be removed? Thanks
Eric Novotny
An informed customer is the Best Customer!
1/28/2014
You could, in theory add another layer of sheathing if you can get it to lay flat. I would not in this case. There is not that much savings in going over the top of the asphalt and in order for the sheathing to benefit from the additional structure, it really needs to lay flat on the primary and 1st layer sheathing.
Dan Blackburn
6/17/2014
I am contemplating installing a standing seam metal roof over existing (20+ yr. old) asphalt shingles. My intention was to install a new layer of felt paper and possibly foam sheeting. The original roof base is 3/8 " plywood so I intend to locate the studs to anchor the new roofing. Is there a better way to install this roof? Should I remove the old roof down to the rafters and start with new 5/8" plywood? I am hoping for the roof to last 40 to 50 years. Thanks!
Todd Miller
Isaiah Industries, Inc.
6/17/2014
Dan, many installations are done like you're saying though I am not a huge fan of foam beneath standing seam. Also, so much depends upon the profile of panel you're installing. What you're doing is more likely to result in a rippled appearance on the roof than would be going over something you know is smooth. You might want to choose your manufacturer and then send them photos and work with them to get their advice on the installation details. Thanks so much and good luck.
Guest User
8/18/2014
Hi,,,,,,I have an asphalt roof on a 4/12 pitch/ranch style home. Am I going to be okay installing a metal roof over the shingles? I am at the edge of a small addition (not fancy at all). I have a tan metal pole barn w/green roof. I am wanting to put on a tan metal roof as my house has pale orange brick w/tan garage door, etc. Afraid to stand out too much w/a green roof. What's your experience with putting on a metal roof w/in an area that's all shingle? I'm probably going to put the house up for sale once remodeled and don't want to goof on this. P.S. Try to ignore the missing barn siding. I'll get that replaced.
Todd Miller
Isaiah Industries, Inc.
8/18/2014
Chances are your roof is a good candidate for installing over the existing shingles, along with a layer of underlayment. A metal shingle roof may fit the best within the current neighborhood but, really, metal roofs of all types are popping up all over in all styles so what may seem unusual today probably won't seem unusual in just a few more years.
Dick Bus
8/18/2014
The market share of residential metal re-roofing is growing. It is now over 10%. It appears that your area excepts vertical seam metal due to do the fact that you have a pole building. According to The Residential Cost Handbook, a reference used by real estate appraisers, reports that the appraised value of a home will increase by $1.35 per square foot - See more at: http://www.metalroofing.com/V2/content/search/?cx=009977283514427421404%3A0kbv3q_vlx8&q=appraised+value+of+home#sthash.mHHh5PKb.dpuf The Metal Roofing Alliance will soon have a visualizer available so that you would be able to see what your roof will look like in different colors and profiles. To insure that you are getting the best value, make sure that you are using products that are manufactured by the member of the Metal Roofing Alliance. Also verify that the contractor has the proper licenses, insurance and visit his references. thanks for considering a metal roof.
Marsha Andrews
8/18/2014
Thank you for the reply. Do you know of any other websites available for seeing the roof on the house? I am very nervous about a metal roof since it would be the only one in my small addition. Can you give me any additional insight or info that would tip the scales for me? Thank you, Marsha Andrews
Dick Bus
8/18/2014
if you give me your address (I promise I will not share it with anyone) I will send you a DVD of our old visualizer. we are in the process of updating it and making it available on the web. my e-mail address is [email protected]
Steven Vela
5/9/2017
My mom has an older hope that sits on cinder blocks. house is about 40' X 65'. Would you recommend adding metal roof over shingles or is this to much weight to the roof? house was recently leveled.
Todd Miller
Isaiah Industries, Inc.
5/10/2017
Steven, really it would require analysis and inspection by a structural engineer for a definitive answer to your question. However, aluminum roofs weigh about a half pound per square foot and steel around a pound. This compares to 2.75 - 4.25 pounds for standard shingles. Additionally, the current layer of shingles has lost some weight due to evaporated oils and lost granules. So, as you can see, the weight factors are very positive for metal.

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