Roofing/standing seam metal over shingles
QUESTION: can standing seam metal be installed over a single layer of shingles by using a slip cover.this is a big project of about 170 sq.some of the metal will be 35 to 40 ft.long.the company we are going to purchase the metal from tell us that they can put a wave in the metal to help the wrinkles when the metal move with the tempature.the pitch of the roof is a 6-12. if we can do this how close do we need to screw it down and what length screws? also what kind of slip cover do we use? note the area we are installing roof is a very windy valley we can't keep shingles on.what about ice and snow breaks on these long runs?
ANSWER: The answer to your question is fairly complex and lengthy. I will attempt to provide some guidance. First I assume you are talking about asphalt 3 tab shingles. While it is possible to install metal roofing over these I advise against this practice. The shingles will telegraph through over time. By a "slip cover" I assume you mean a product like an ice and water shield. This would help but I still advise against the practice. The type of roofing panels you are planning on using is also a factor. The wrinkle effect you refer to is oil canning and it exists in all panels. It can be minimized by using a heavier gauge panel, a lighter color and minor ribs. All of these factors will reduce the oil canning but it will not eliminate it. Another factor is your roof pitch. This can also emphasize the oil canning. As for fastening the panels to the roof this is generally accomplished using concealed clips and screws. The design and engineering of the panel dictates the spacing of the clips. To completely answer the remainder of your concerns will require more information. I hope this provides you a better insight into your project. Please feel free to contact me if you need further assistance.
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QUESTION: the slip cover that I am asking about is a material used to cover up the shingles it will be the same thing used on new installation of metal roofing synthetic or astm1970/d197om-13 standard specification for self adhering polymer.will this not be enough to protect the bottom of the metal?we are using 26 gage metal.what is minor ribs and what does the telegraph through mean? the shingles are 3 tab 120mph rating.thanks for the input it will be helpful in our decision for this project.
First off, telegraphing is the act of the materiel below, the old shingles, showing through the new materiel. This occurs as the roof "settles" in and conforms to the substructure. In your case the underlayment will help reduce this, but I would still expect some. Secondly, I still do not know which manufacturer you are using and which exact product. Some of the products lend themselves better to an installation of this type. Minor ribs are additional shallow ribs in the flat of the panel to help reduce the oil canning effect. Finally, the 26 gauge materiel is too light, particularly for this installation. If you are going to use 26 gauge material I would definitely strip the old roof down to the roof sheathing and put the underlayment materiel on that you are planning to use.
Hope this helps.