Roof Damage Repair:
About Laying New Roof Shingles Over Old Shingles
Some roof repair companies layer new shingle over old ones for convenience and cost. But if you hire a roof repair company that skips the tear-off stage of your roof repair project it will end up costing you money in the long run.
At Aaron’s restoration we never “layer” old shingles over new ones – and here’s why:
Why You Should Not Layer Shingles when Repairing a Roof
The process of removing the existing layer of shingles is called a tear-off. A tear off is time consuming and labor intensive. So when a roof repair company cuts corners and doesn’t do a tearoff, the roof project goes quicker and they save money.
But if your roof repair company takes this shortcut and layers instead of properly tearing off the existing shingles, within just a few years your new roof – which should last 25 years or more – will start to fail.
Double Layers of Shingles Reduces Roof Repair Lifespan
Shingles are designed for flat surfaces. So if you try to adhere them the gaps, dips, humps, and textures of the existing shingles they will not stay on over time.
Shingles can weigh 350 to 450 pounds per 100 square feet of roofing, installed). And your roof structure was only designed for a dead load of one layer of shingles (with a safety margin for snow). Installing new roof shingles over old shingles doubles the weight of the roofing, and your roof structure may not be able to handle the extra load.
In fact, building codes commonly prohibit “double shingling” or limit re-roofing to no more than two layers – for safety reasons. So layering shingles can actually be a code violation.
Without a tearoff, the roof repair company cannot see what condition the decking is below the existing shingles – so they will miss underlying structural repairs that are needed to the structure below. This can result in leaks and even collapse.
Also, layering roofing may affect the warranty on the new shingles. Additionally, layered shingles are going to be a red-flag on any inspection report of you ever sell the house!