If you're having your old asphalt roofing replaced or repaired, you may be wondering what the process entails. You know the shingles have to be replaced, but you may not be familiar with what's underneath the shingles or how a roof is built. An asphalt roof consists of three basic parts: the sheathing, underlayment, and shingles. Here's a look at how they form a roof and what a roofer does to them when replacing or repairing your roof.
The Roof Deck
The roof deck is also called sheathing. It's usually made of plywood, but other types of boards are sometimes used. The plywood provides the surface for building up the roof, and it also plays a role in the structural support of your roof.
When you have a roof leak, the deck can get wet and rot. This might cause your roof to sag or even cave in if the damage is bad enough. Generally, your roofer will just remove the damaged areas and replace them with dry plywood and continue with the roofing project. The entire deck isn't torn off when getting a new roof unless most of it happens to be damaged.
Underlayment is another important part of your roof. Underlayment can be made of different materials, such as felt or synthetic materials. Some have a sticky backing so they fuse to the deck for added water resistance. The purpose of underlayment is to cover the deck and provide protection from water that leaks under the shingles.
Underlayment is also useful when putting on new roofing since it protects the deck if it happens to rain before the new shingles are put on. Underlayment can wear down as the years progress, so when you get a new roof, it will probably be torn off so new underlayment can be applied. The roofer may even need to cut out damaged underlayment and patch in new underlayment when making repairs so the deck has the best protection from water.
Once the layer of underlayment is on the deck, shingles can be applied. The asphalt shingles are put on so they overlap, and this normally keeps rain from getting under them. The shingles protect the deck and underlayment from rain and from UV damage. Asphalt shingles have a top layer of tiny granules that protect the shingles from UV rays. The granules wear off over time, and this is what causes your roof to age.
You may have heard you can get a new layer of shingles if your roof only has one now. If your roof is in good shape, that might be possible. However, the main benefit of tearing off your old roof, even if it has only one layer of asphalt shingles, is so the roofer can inspect the plywood sheathing and replace the underlayment too.
Contact a roofing company for more information.