Why Roofing Over Old Shingles Is Not Usually A Good Idea
Usually, when you have a roof replaced, your roofer will remove the old roof and then put a new one on. Sometimes, though, people instead put a new layer of shingles right over the old layer of shingles. Most roofers recommend against this; it's typically only done when homeowners are on a really tight budget or when a home is slated to be removed and just needs a few more years out of a roof. Why isn't this approach more popular? Here are a few key reasons.
Moisture can get trapped between the shingle layers
It can take a roof a few days to dry out after a rainstorm. It may appear dry, but there may still be a small amount of moisture lingering in or between the shingles. If you simply have a new layer of shingles on top of the old one, this moisture will be trapped. This, in turn, can lead to mold growth and shingle deterioration. It is much safer to simply tear off the old roof and put a new one on.
Your roofer does not get to examine the roof deck
The roof deck is the wood that forms the base of your roof. If your roofer strips off the current shingles, they'll expose the roof deck and be able to note any rotten or deteriorating spots. They can then replace or repair these parts of the roof deck. If your roofer does not strip off the old shingles, they won't get a chance to examine the roof deck. If there is damage, it will go unnoticed, and it may lead to bigger issues like a sagging or bowed roof in the future.
Your shingles' warranty may be invalidated
Shingles come with a warranty. In most cases, the warranty terms require that the shingles are installed in a specific way in order for the warranty to be honored. If the shingles are put over an existing roof, then the shingle company probably won't honor the warranty. This could mean that you end up paying for any necessary repairs or shingle replacements out of your own pocket.
On occasion, roofers will put new shingles right over the old shingles. However, as you can see, this is often a risky approach, which is why most roofers recommend against it. If you were thinking of re-roofing over your old shingles, consult a roofer before doing so. They can give you more personalized guidance in this regard.
To learn more about residential roof replacement, reach out to a roofing contractor in your area.
