You might be able to get away with adding a second layer to an aging shingled roof, if the old surface is still good, and perfectly level. But then why would you want to do that when it’s not necessary yet? Besides, there are other drawbacks to shingling over shingles you may not know.

It’s Hard To Be Level Over Bumpy Surfaces

Asphalt shingles, and wood ones for that matter curl on the edges as they dry under the heat of the sun. This makes it almost impossible to properly install new ones over old. But aesthetics aside, it also increases the likelihood of moisture getting past the overlaps.

You Are Adding Extra Weight to Your Walls and Foundations

A 2,000-square-foot roof requires 20 squares of shingles, or 60 bundles. Those 20 squares could weigh as much as much as four tons. We can’t recommend doubling the weight of a roof on an average home.

It’s Impossible to Inspect the Underlying Surface

Having a new roof fitted is a great opportunity to inspect the condition of your underlayment, which is after all your waterproofing of last resort. We have uncovered horror stories stripping away boards, that turned out very expensive to repair.

You Don’t Know the State of Your Water Leak Barrier

Water leak barrier technology has some a long way over the past few decades. However, an aging shingle roof may conceal developing, or very real problems. Another drawback to shingling over shingles is we have more stripping to do, to trace a leak.

Covering Over Can Add More Complications

Shingle suppliers we know could invalidate their warranties if we were to shingle over shingles, which we generally don’t. Your insurance company could look twice at any water damage claim. Some building codes prohibit roofing over roofing.

The Big Drawback Is It’s Often a False Economy

You could save a few a few thousand dollars perhaps, by shingling over an existing shingle roof. We have known of unscrupulous sellers doing this as a cover-up. However, if you are planning on keeping your home, then a cheap fix could turn out expensive in the long run.

Speak to Valiant Exteriors for Honest, Objective Advice

Your home is your largest investment. You need to look after its roof and its value. Home inspectors have begun checking carefully, because they know the drawbacks to shingling over shingles, and they will report these to a potential buyer.

Give us a call at (403)829-1661 or write us an email to [email protected] before you sign for a shingling-over-shingles job. Allow us the opportunity to run the numbers with you, and explain why doing the job properly does not need to be more expensive, viewed over time.

More Information

How Roof Pitch Affects Your Pocket

A Good Roof Is More Than a Low Price

Cat on an Asphalt Shingle Roof: Dwight Sipler BY CC 2.0