A roof installation can be as simple as a roof shingle replacement, but sometimes it may also require a replacement of the plywood decking beneath the shingles. It's important to know when to replace the roof decking.
1. Major Punctures
A small puncture doesn't necessarily mean you need new decking, as small damages can be patched rather quickly and effectively. A larger puncture that damages multiple decking boards or that isn't repaired right away is typically best to replace during the same time you have new shingles installed. Major damages are more difficult to patch effectively, and large damaged areas often have an increased likelihood of leaking later.
Roof decking should always lay perfectly flat. Any warping means that the wood fibers have become damaged, likely by moisture incursion from a previous leak. Installing shingles over warped decking doesn't work well, as water will seep beneath the shingles if they aren't lying flat. Any bump or wave in the surface can lead to a leak, which will mean more damage can occur and you will need to replace the roof prematurely.
3. Moisture Rot
Once moisture gets into the wood, it causes the fibers to swell, which then causes the fibers to break down. Microorganisms can also start to move in and begin further breaking down the wet, weak fibers. This process often can't be stopped once it begins, and soon the entire decking board will rot. The rot can also spread to neighboring boards. If there are any soft rotten spots on the decking, then replacing the decking is the only viable option.
4. Mold Growth
You can sometimes check the state of the decking without removing the shingles first. Moisture damages often produce mold and mildew. If you have access to your attic, you can check the underside of the decking boards for the dark spots and musty odors that indicate mold growth. Inspecting the underside of the decking can also reveal small punctures and other issues, like areas that are beginning to rot.
Eventually, decking should be replaced due to age. When a roof is installed, thousands of nails are driven into the decking in order to secure the shingles. After two or three roof replacements, the number of nail holes left behind will severely compromise the protection of the decking. There is also an increased chance of nail popping since nail holes will become larger each time a new nail is driven into them. Multiple replacements will mean it is more difficult to nail in a fresh spot on the old decking.
Contact a roofing installation service to learn more about roof replacement options.