If you're thinking of getting a new roof soon, you may want the new roof put over your old asphalt shingles. Some roofers offer this service and others may try to talk you out of it. There are advantages and disadvantages to having two layers of asphalt shingles.
You'll want to discuss all of them with your roofer so you make the right choice when you get your new roof put on. Here's why your roofer might want you to avoid two layers of roofing if possible.
The Roof May Be Harder To Repair
Reasons for putting a second roof on your home include the installation of the new roof going faster and the job being cheaper since the old roof doesn't have to be torn off. Adding a second layer over your existing roof might make your roof installation less expensive, but you may find repairs are more costly in the future since the roofer has to rip off two layers of shingles to hunt down a roof leak.
Not only that but water can get trapped between the layers of roofing and lead to the rotting of the deck, which makes roof repairs more difficult and expensive.
The Second Layer Adds A Lot Of Weight
Your local codes may allow for two layers of asphalt shingles, but it's important to remember the second layer adds a lot of weight. If a big snowfall dumps a lot of snow on your roof, the combined weight of two roofing layers and snow could lead to structural roof damage.
Codes usually prohibit a third layer of roofing, so the next time you get a roof replacement, you will need to have both layers of roofing removed, and that could end up costing more than if you just have a single layer taken off.
The Roofing May Not Last As Long
Your roofer may tell you a second layer of asphalt shingles won't last as long as a new roof with one layer. That's often because two layers cause the roof to heat up too much. Excessive heat can damage shingles. That's why your roof has passive ventilation through the attic.
Your roof might even have a turbine vent on top to help prevent damage from too much heat. There's not much you can do to stop heat damage, so you'll need to be prepared to replace the new roof sooner than you normally would.
Contact a company like Crossover Roofing to learn more.