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Recently had a metal roof installed and have a few questions regarding standard installation practices.
Question 1: Is it standard practice to shim or fir purlins if the existing roof surface has sags or low spots? My home is over 100 years old and has an area that sags slightly. The installer did not fur the purlins in an attempt to level and panels in that area exhibit some "oil canning" as a result. Is it out of the ordinary to assume that the installer should have strung a line and used shims to bring the surface to level within some measurement of tolerance?
Question 2: Is it standard practice to use some sort of under-layment beneath a metal roof when installing over existing shingles. ie (roofing felt, ice and water etc.) My roof was installed over the existing three tab shingles with no under-layment used?
Thank you for your time and attention.
In regards to shimming and trying to level things out. Sometimes it is done but frankly it takes a lot of time and effort and in many cases it would have been better to address the core issue before starting the roof. This is one of those things that the contractor and homeowner should discuss before ever signing a contract.
In regards to underlayment, what was done on your roof is not unusual. That said, I personally interpret the International Residential Code of the ICC as requiring underlayment even if battens are used. However, most folks including even many building inspectors do not interpret it that way.
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