Pennsylvania allows two layers of shingles at most. Its building code follows the International Residential Code (section R908.3.1.1), which says a new roof cannot go over a roof that already has two or more layers, over slate, clay, cement or asbestos-cement tile, or over a roof that is water-soaked or too worn to hold another layer. Your city, borough or township can tell you how it applies where you live. When asphalt shingles reach the end of their lifespan, signs include constant leaks, shingle loss, and mold that may force a roof replacement. However, replacing an asphalt shingle roof without a good budget can be overwhelming.
Layers of Roofing: Risks and Benefits
A new roof normally starts with tearing off the old one. If the sheathing underneath is too damaged to hold the new roof, it has to be replaced as well.
Sometimes a new layer of shingles can go over the first one instead, but only if the sheathing and roof structure are still sound.
How Far to Take Your Roof Overlay
A full roof replacement can be expensive. There are expenses for buying new shingles and disposing of the old roof. Under the code, a roof can have two layers of shingles at most, so a third layer is not allowed.
A second layer may be added to an existing roof unless:
- You already have a double layer of shingles or two or more roof covering applications.
- The existing roof is slate, clay, cement or asbestos-cement tile.
- The current material is water-soaked, or the roof structure is not strong enough to hold the second layer of shingles.
Before any overlay, the roof deck must be properly inspected to determine whether it’s eligible to hold more roofing components.
Experts will need to also check the roof flashing, the old shingles, and other roofing components to ensure they are all in good order. Even if your existing layer is in great condition, and the roof is eligible for re-roofing, we still recommend a full tear-off.
Are There Benefits to More Than One Layer of Shingles?
Where the code allows it, a second layer can go over one existing layer of shingles.
Here is what an overlay can save you:
Cost saving
It takes a lot of money to tear off a roof. There are significant costs involved when stripping the old roof and installing a completely new layer.
Aside from replacement costs, there are also costs to dispose of the old shingles and other materials. You can save on all of these costs by simply adding another layer.
Saves time
There is actually a lot of time involved in the entire replacement process. Skipping the tear-off makes the job shorter.
With no tear-off, the roof deck is never left open to rain.
Should You Add a Second Layer?
A second layer can cut the labor cost of a new roof and make the job easier. But should you do it?
We don’t recommend it. A single layer of new shingles improves your home’s curb appeal while saving you on future costs. Here is why a full replacement is better than a second layer of shingles.
Roofs are more than just layers of the material
A roof is a system, not just layers of shingles. The roofing system protects the home interior from elements like high winds and rain and keeps the energy in. It’s a system of barriers featuring flashing and counter flashing, waterproofing, a wooden roof deck, shingles, and more.
Adding on a second layer blocks you from checking the other elements. It becomes hard to inspect the roofs.
Re-covering affects the warranty
A second layer can change the manufacturer’s warranty on the new shingles, so read the warranty terms before you choose an overlay.
This can cost you more in case the roof has a serious issue. New underlayment can only go down once the old roof is off.
The extra weight
A second layer adds the weight of a whole extra roof of shingles, and its nails have to be long enough to reach through both layers into the deck.
Your building may need more structural strength to handle such factors. Or the roof could already be weak and damaged. A roofer should check the structure before any overlay.
Future costs
You may avoid the roof replacement costs now, but understand that you will be dealing with more material when you want to replace the roof in the future. You now have two roofs, which could make disposing of them more expensive.
Are You a Good Candidate for a Roof Overlay?
Certain roofing situations may require a complete tear-off, where repairs are no longer applicable. Homeowners in PA can have up to two layers of shingles. Here are some conditions that are right for re-covering:
- The roof itself is not rotten or damaged. Your roofer may need to thoroughly inspect the roof before determining its eligibility for an overlay. You can have another layer if the roof is still in good condition.
- Your roof has only one layer of shingles now.
We recommend that you replace the existing material. But if you choose to use an overlay, then you must consider several factors. These include the warranty terms, extra weight on the roof, future repairs/replacement, and insurance coverage. Also, if your current roof is severely damaged, a full replacement is your best option. Call In The Light Roofing at (484) 553-0213 for a free estimate.