Installing a new roof over old…not a good idea
Two layered roofs, 2 different homes.
Looking to install a new roof? Most big box stores carry shingles composed of a heavy fiber glass mat base and ceramic-coated mineral granules that are tightly embedded in carefully refined, water-resistant asphalt.
Installing a new roof over existing is not a viable solution for a home owner looking to stay in their home. The only time this makes sense is when your flipping the house or moving out in a short amount of time.
It’s cheaper than installing a new roof, because you’re not stripping off the old roof, no waste fees.
· Faster installation installing over existing, less work involved.
· Some local building codes allow two layers of organic or fiberglass asphalt shingles on roofs with a 4/12 pitch or less, and three layers on steeper roofs. Check with your local town building inspector.
No warranty, installing new over existing roof voids warranty. At best you “might” receive a 1 year warranty from the installer.
· Without a complete removal of the old roof you can not examine the roof decking / sheathing under the roof, hidden problems may exist.
· Depending upon the size of your roof, you’ve added multiple tons of weight, which could pose a big problem if there is significant snow accumulation.
· The new roof will breakdown fast, 10 maybe 15 years tops. Even if you install the best 35yr architectural shingle. The old roof will eat away at the new roof. See above photos is this what you want?
· Nail pops, are nails back out lifting shingles. In some cases, causing shingle blow off during high winds. See above photos, two different homes same problem.
· Higher cost to replace a multilayered roof, more shingles to dispose of.
· Roof prep, if you don’t clean off moss, fungus and lichen on the existing roof it can pass through the sheathing below creating moisture damage and mold. See below photos, this will be a very expensive repair. The black stained plywood decking is soft, mold covered and dripping wet.
In my opinion, spend a little more doing it right by stripping off the old roof this will save you money in the long run.
Most towns in NH require a building permit to install a new roof. Some contractors will tell the home owner to pull the permit. DO NOT DO THIS. If you do, you just assumed all the responsibility of the roof being installed correctly and not the contractor.
Last, liability insurance, most contractors will tell you they have it. However, you need to see the policy and verify whose names are on that policy. If there is a worker on your property that is not listed and they get hurt the claim goes against the home owner.