When it comes to placing new shingles over old ones, it is only feasible with asphalt shingles. Slate or wood cannot be overlaid with new shingles, and mixing materials like asphalt shingles and cedar shakes is strongly discouraged. One crucial rule for overlaying new shingles on top of old ones is that the existing roof must be in good condition. If the current roofing system has numerous leaks or damage, adding new shingles will not be beneficial. Long story short, you can cover old shingles with new shingles, but you probably shouldn’t.
Should You Consider Installing New Shingles Over the Existing Ones?
While having multiple layers of shingles may appear to offer extra protection for your roof, it does not automatically enhance its waterproofing capabilities. In fact, having multiple roofing layers can introduce its own set of problems.
The primary benefit of installing new shingles on top of the old ones is convenience and cost savings. Keeping the old shingles allows you to avoid the messy labor and disposal expenses associated with a complete tear-off.
To ensure proper installation of new shingles over old ones, special preparation work is required. This includes, among other things, removing ridge caps, and vents, and correcting any irregular angles. Additionally, when working with old roofing, it may be necessary to replace or add new flashing, which can be difficult. While you may initially save on tear-off costs, you are essentially deferring the expenses.
Reasons to Avoid Adding New Roofing Shingles Over Old Ones
Despite the small benefits mentioned above, there are several universal reasons why shingles should not be overlaid. Here are some things to think about if you’re thinking about covering your old shingles with new shingles.
The Weight Consequences of Shingle Overlay
Your roof is built to support a certain amount of weight, taking into account the shingles and potential snow accumulation. Adding extra materials on top of the structure increases the load on the structure. This raises questions about the capacity of your current roof structure. Overloading the roof can jeopardize its stability and increase the risk of collapse, making the structure of your home unsafe.
Shingle Compatibility with Flat Surfaces
Shingles are not intended to bridge gaps, humps, or dips, including the stepped texture formed by overlapping shingles. Even with the expertise of experienced roofers who may have techniques for overlaying new shingles, there is still a possibility of curled, cupped, or misshapen shingles.
These flaws will be transferred to the new layer, jeopardizing its appearance and functionality. If you must overlay your roof, use laminated or dimensional shingles, which are thicker and have staggered edge profiles to hide any imperfections in the old roofing.
Lack of Proper Visual Inspection of Underlayment
Roofers cannot visually inspect the decking beneath without removing the existing shingles. A reputable roofer would typically perform a thorough “walking” inspection to identify spongy areas and other issues. This enables localized repairs prior to the re-roofing process. If you hire an untrustworthy roofer who fails to perform this inspection, your roof becomes vulnerable to any existing damage that may penetrate the new layer of shingles.
Contact PJ Fitzpatrick for Your Roofing Needs
There are a multitude of reasons why you should not cover old shingles with new shingles. While it’s understandable that some homeowners prefer to avoid the upfront costs of a new roof installation, it is more beneficial in the long run to refrain from overlaying. The reasons stated above should be enough to discourage you from simply layering new shingles over old ones. While you may save money in the short term, you will undoubtedly pay more in the long run. If you live in the Mid-Atlantic region, contact the expert roofers at PJ Fitzpatrick for a quote.