Can You Lay New Roof Shingles Over Old?

Can You Lay New Roof Shingles Over Old Ones?

Yes, it is definitely possible to lay new roof shingles over your existing shingles. However, there are certain conditions that may not support the process and you may need to remove your old shingles in order to install the new ones. Notably, you can add a new roof over an old one only if you use asphalt shingles as they are lighter in weight compared to other options such as wood and slate. Additionally, you cannot mix materials. For instance, asphalt shingles cannot be laid over cedar shakes. Most importantly, you can choose to add a new roof over an old roof only if the old roof is in good physical shape.

Reasons why you may choose to install new roof shingles over the old ones

Installing one roof over the other does not necessarily mean that you are going to get a stronger roof that can demonstrate better waterproofing qualities. In fact, layering has its own set of problems. Then why would you still want to install new shingles over the old ones? Well, by installing new shingles over the old ones, you can skip the laborious job of removing the old roof and save some money as well. While it may seem to be an easy process to leave the old shingles back in their places, you may need to take some special preparations to support a re-roofing job. For example, you may need to add or replace new flashing or you may need to remove the old vents, ridge caps, and the deformed shingles.

You can save as much as $1,000 if you can skip the old roof removal job, but you are most likely to incur greater costs in the near future when you need to replace and dispose two layers of roofs to get a new roof installed. In most areas, homeowners are not allowed to use more than two layers of roofs and some building codes do not permit re-roofing at all. For instance, you will not be allowed to install multiple layers of roofs if you are located in a region that registers heavy hailstorm or snowfall incidents.

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Reasons why you may not choose to install new roof shingles over the old ones

  • Shingles can cover flat surfaces and there are chances that they may fail to cover the irregularities that are associated with curled, cupped, or distorted shingles. Your roofer may recommend the use of laminated or dimensional shingles that are normally thicker than the standard shingles and have the ability to conceal dips or low spots in the old roof.
  • Layering increases the weight of your roof. Your roof might have been designed to withstand the weight of one layer of shingles, the weight of snow, and the capacity might allow for a safety margin as well. Normally, composite shingles weigh between 350 pounds and 450 pounds per square feet of roofing and the addition of another layer of roof increases the weight further. So you need to make sure that your existing roof can withstand the additional load.
  • An experienced and honest roofer will conduct a visual inspection of your roof’s decking to diagnose and rectify critical issues before re-roofing. However, if you are not working with a good contractor, you are more likely to get a new roof installed without evaluating the condition of your decking, which may lead to issues in the long run.
  • A re-roofing job does not involve the replacement of the tar paper that is placed between the shingles and the roof sheathing. Even if you install multiple layers of shingles, water may still pass through them and enter your roof deck. The tar layer prevents the entry of water into your roof deck and if it is old and deteriorated, it will fail to restrict the entry of water in your roof deck. Homes that are located in snowy climates normally feature roofs that are equipped with an ice-and-water shield. A re-roofing project does not include this option and the extra layer of shingles may fall short of providing adequate protection.
  • Re-roofing may have an adverse impact on the warranty on the new shingles and so you must seek clarity about warranty from the shingle manufacturer before initiating the re-roofing project.

Homeowners who are looking to sell their homes may find re-roofing a cost-effective option. New owners are most likely to bear the cost of a double-layer tear-off along with other additional charges that may be associated with an improper re-roofing job. This is the reason why potential home buyers are often warned about the presence of double-roofs and the problems that re-roofing may entail so that they can make informed decisions. If you are planning to sell your home, you may want to consult your local real estate agents and contractors to assess your options.

Have questions? Contact us and we will be happy to answer your questions and clear your doubts.

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