Spending my early years as a roofer brought to my attention a lot of questions about new roofs, tear offs, leaks, products, etc… The question that presented itself over and over went a little like this: “Is it better to roof over my existing roof system, or should I tear it all off and start new?” Ask three different people and you will probably get three different answers, well maybe two different answers with three different explanations, anyway the math isn’t important. What is important is for you to know how to answer this question yourself.
If you think about it, a builder or contractor is going to do their best to sway you to do what is most convenient for them, not to mention the most profitable. You see it really doesn’t matter which one you do as long as your home or building can handle a new load. Most residential homes can handle up to two loads of shingles, as long as you are not changing the type of roofing system you should be okay. How do you find out if your roof can handle a double load, you ask? The answer is simple: Call your local city or county building inspector. It is their job to know things like that, and the best part is it is free of charge. After all they work for you.
The arguments for or against tearing off can persuade a homeowner to go, well, either way. That is the beauty of the question, for us roofers anyway. Some people will say that the shingles will not last as long if you layer them on top of each other. That makes sense, but why would shingle manufacturers allow a warranty on the shingles if that were true? After all, instructions for layering shingles are right on the package, it is called re-roofing. A verse from out of the re-roofers corner would go something like: it saves you landfill costs and helps the environment by producing less waste. That would be worth every penny, if shingles lasted forever. Eventually, weather in your lifetime or someone else’s they will have to come off. There are very few building codes, if any at all, that allow three layers of any type of roofing on residential homes. (For all the technical junkies, I know that built up roofing systems are layered, but I am going with the majority here, okay)
These arguments can go on and on, kind of like a quantum physics equation. My point is this; it is really up to you, the homeowner, to make the decision based on your individual needs. Don’t feel bad if you decide to save some money and re-roof, just because the next owner will have to pay double the landfill charge doesn’t mean they didn’t deserve it. And if you want to tear-off, by all means do it. Don’t let a roofer or a contractor tell you what is best, do a little research and plan according to your needs.