How Many Layers of Shingles Are Allowed on a Roof?

Replacing a roof is a major investment, so adding a layer of shingles instead of replacing your roof may be an appealing option. Adding a layer of shingles—also called re-roofing or overlaying—may not always be a good choice. Local building codes, roof warranties, and your home’s ability to support the weight of extra shingles can all limit how many layers of shingles your roof can have. Our guide breaks down how many layers of shingles are allowed, when you should consider re-roofing, and why multiple layers of shingles may not be a good idea. 

How Many Layers of Shingles Can Go on a Roof?

An asphalt shingle roof can have a maximum of two layers of shingles. Most local building codes limit the number of layers of shingles a roof can have, and having more than two means you’re most likely violating building regulations. 

Not all roofs can have two layers of shingles—your roof pitch, the type of shingles, the condition of your existing roof, and your roof’s structural support are all contributing factors that may limit you to a single layer of shingles. Consult with a local roofer to find out if re-roofing is an option for you.

Reasons to Not Add Multiple Layers of Shingles

Even if you’re allowed to have multiple layers of shingles, it might not be a good idea. There are some serious problems with two layers of shingles that may occur, so it’s smart to familiarize yourself with some of the issues you may run into.

• Adding a layer of shingles may void your roof warranty.

• The added weight of more shingles can cause structural problems like cracks in the foundation and damaged roof supports.

• Another layer of shingles can hide existing damage, including deteriorating roof decking, damaged roof flashing, leaks, and rotting wood.

• A second layer of shingles can cause or worsen mold, rot, and pest problems.

• Future damage will be more difficult to locate and repair.

The potential cost savings of re-roofing can be appealing, but you may find yourself facing expensive repair bills in the future.

When to Consider Re-Roofing

When you start having roof problems, you may wonder if you need a roof replacement, if you should replace damaged shingles, or if re-roofing is the best idea. Your roof may be a candidate for re-roofing if:

• The current roofing materials and decking are in good condition.

• Your roof’s support structure is capable of holding additional weight. 

• Your local building codes allow for two layers of shingles.

• You’re planning to sell your home—re-roofing is a shorter-term solution than replacing a roof. 

• Your current roof is less than 15 years old—shingle roofs reach the end of their lifespan at 20 to 30 years, so older roofs should be fully replaced instead of re-roofed.

Cost to Add a Second Layer vs. Roof Replacement

The average cost of a shingle roof replacement ranges between $7,500 and $24,000. An overlay of new shingles could save you 20% to 40% of the cost of a full roof replacement since you won’t be paying for the removal and disposal of old roofing materials, and the labor costs will be lower for the shorter project time. If you do choose to re-roof instead of replacing your roof, choose a roofer with overlay experience to minimize the potential problems.