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Question DetailsAsked on 10/26/2014

when tearing off old roof shingles which are over ice shield,what is the best way or should i shingle over both?

the shingles are stuck to the ice shield and the ice shield is stuck to the plywood.

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If you shingle over (other comments on this issue of overlaying in the Home > Roofing link in Browsw Projects, at lower left), you can void your shingle warranty, probably knock 5 years or so off their life, in many cases (especially with architectural or "3-D" shingles) increase susceptibility to wind damage because they do not lay as flat, end up with a less than uniform roofing appearance (wavy or rippled), and perhaps most importantly you are counting on the probably 20-30 year old underlayment (roof wrap or roofing felt or ice shield, as in your case) being intact and usable not only now but for the next 30 years or so - which is asking a lot of it, especially if not asphaltic mastic ice and water shield.


How to get it off - depends on the brand and how well it has stuck and what the temperature is when removing it. Some work better removing the bulk of the shingles first (leaving those who stick badly), then peeling the ice shield off diagonally from one corner - one or better two or three people pulling (being careful not to back off the roof) and one other person going along on the exposed surface with along-handled driveway ice scraper like a Mutt (but sharpened) breaking loose the places it sticks to the sheathing. Other brands, or if really badly stuck, heating from the top or at the peel point with a high-capacity heat gun (safer) or a propane blowtorch (riskier and should have a hose on standby on the roof)) to soften the adhesive/tar is necessary. Sometimes it is so stuck to the asphalt, or not badly stuck to the sheathing, so you can just use normal shingle removal tools and ice scrapers to peel both the shingles and underlayment off together, same as you would with roofing felt.


Leaving it on is iffy - because multiple layers of underlayment, even if it lies flat now, can result in bunching and creasing when it heats and expands, which will reflect through to the shingles and void the warranty. However, especially with roof edge ice shield (along the 3-6 feet along the lower edgesand under valleys), if in good shape and not creased or bunched it is not uncommon to leave it on and either overlay it (questionable practice) with a new layer, or just reuse it as is (bad practice because that assumes it is good for another 30+ years, and also that the prior nailholes will self-seal and not leak.


One other method I have seen, especially with Grace Ice and Water Shield (my favorite) is using a portable high-temp steam generator to heat the peel edge as it is peeled back - used by larger roofing crews, and you have to be careful not to get asphalt-stained water running onto siding and such.

Answered 4 years ago by LCD




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