A roof replacement is a huge endeavor for a homeowner. Often, you may wonder whether it is necessary to have your roofing contractor go through the whole process of tearing off the old roof. Wouldn’t it be much easier to simply install the new shingles over the old? Here’s some information to point you in the right direction:
Installing New Shingles Over Old Ones
It is legal in Canton and other Michigan communities to install new shingles without a tear-off when doing your own roof and provided the condition of the roof allows it. The exact meaning of what does and does not qualify is subject to much debate. However, weight limits of your home’s structure and manufacturer warranties typically void the option of reroofing without a tear-off of old materials.
Why Tear-Offs are Almost Always Necessary
Roofing contractors are often required to perform a tear-off before installing new shingles, either legally or for the purpose of manufacturer warranties. In most cases, more than two layers of roofing shingles does require a tear-off.
Laying new shingles over old shingles is easily prone to leaks and reduces the life of the new shingles. This alone ought to be reason enough to do a tear-off; it’s just a bad value not to. But there are other sound reasons to do the tear-off:
- Only after a tear-off can the roof decking be inspected properly for rot, mold, and other damage that would diminish the integrity of your new roof. (Victors Roofing automatically includes up to four sheets of OSB roof decking because wood replacement is a normal and expected part of the process.)
- Roofing shingles are heavy! With the snow and ice you already have to be prepared for on a Michigan roof, the last thing you need is extra weight from more than one layer of shingles.
- Ice damming is a definite problem on homes in Canton and Southeast Michigan. Many local codes only require 24″ of ice and water barrier under the shingles. After last winter, many a homeowner here in our service area found out the hard way this is not nearly enough. By doing the tear-off, our standard procedure is 6′ of ice and water barrier before installing new shingles.
- Underneath your shingles is a layer of underlayment. If your shingles are getting old enough to need replacement, so is your underlayment. Also because your roofing is older, the underlayment would most likely be felt material which is not nearly as durable as the new synthetic materials.
- Warranty is also a big issue. Although some shingle manufacturers claim the warranty is the same whether you do a tear-off or not, watch out for the fine print. You’ll be dealing with depreciation by the time your roof fails and won’t likely be getting full replacement costs under the warranty. Reputable shingle manufacturers know that installation, combined with the use of the ice and water barrier, along with underlayment, are key to the performance of the roof. Material warranties are structured accordingly.
For all the conflicts of information you will find if you research this question, realize this: you won’t find a true roofing professional that doesn’t advocate the tear-off. There are plenty of people who will tell you it’s not necessary, but they don’t have to come back and replace your roof for free if it fails.