If your home's due for a new roof, then you may have heard about having an additional layer of roofing installed over your existing roof as an affordable and popular alternative. But before you jump on this home improvement opportunity, you may want to consider if a roof overlay is worth installing on your home. The following outlines some of the considerations to factor into your ultimate decision.

Consider the Potential Savings

According to Angie's List, the average cost to have a professional tear off your existing roof and replace it with a single asphalt shingle layer could cost anywhere from $5,000 to $12,000 based on a typical 2,200 to 2,600 square-foot roof replacement. Much of that cost includes the labor needed to remove the old roof and the expense of properly disposing the old material. In comparison, simply adding another layer onto your existing roof can be a less expensive alternative to a complete tear-off.

Many homeowners tend to overestimate the potential cost savings of a roof overlay when the savings are actually somewhat modest, however. Angie's List notes that you could see a 25-percent savings when compared to the cost of a complete tear-off and rebuild. While the savings is there, it may not completely account for any long-term costs associated with maintaining and repairing a roof overlay.

There are also potential warranty issues to consider. While most shingle manufacturers don't discriminate between a clean install and a re-roofing, some manufacturers may reduce or even void warranties based on this installation method. Considering how a warranty could save you thousands of dollars if problems surface with your roof, it's important to understand how much warranty coverage is offered and how it applies.

Consider the Condition of Your Existing Roof

Another factor to consider is the current condition of your existing roof. Any signs of damage or severe wear and tear on your existing roof could easily limit the lifespan of the roof overlay. For example, curling or crumbling asphalt shingles can make it difficult or even impossible to lay new shingles over the existing roof system. Installers may also have a difficult time bridging shingles over areas with dips, gaps and humps in the roof structure, making the installation process more complicated and time-consuming.

It's important for you and your roofing contractor to evaluate the condition of your existing roof before committing to an overlay. Since a visual check of the roof sheathing won't be possible without a tear-off, your contractor may attempt to check the sheathing for any soft spots by carefully walking along the entire roof.

Consider the Added Weight

Adding an additional layer over existing shingles can also add weight to your existing roof. Typical 3-tab asphalt shingles can weigh as much as 200 pounds per square (defined as 100 square feet of roofing when installed), while high-quality laminated shingles can tip the scales at 500 pounds per square. The added weight can take a toll on your roof's framework unless it's designed to handle the extra load. For example, it's not uncommon for a roof overlay to cause a roof to sag in certain areas.

It's crucial to have your contractor verify your roof's structural integrity and load capacity before overlaying additional shingles onto your existing roof.

Check Your Local Codes

The decision to re-roof your home over existing shingles could come down to what your local municipality's building codes allow. While most areas allow re-roofing, some places may not allow the practice at all. This is especially true of areas where hailstorms or ice dam issues are commonplace.

Local codes may also have limits to how many layers can be added on a typical residential roof before a complete tear-off becomes mandatory. According to InterNACHI, most building codes only allow a maximum of 2 to 3 layers depending on the pitch of the roof. It's important to check the building codes for your local area before having new shingles installed over your home's existing shingles.

For more information on whether layering over your existing roof is worth it, contact a company like All American Roofing Incorporated.

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