There are pros and cons to going with either installation option. At Tim Leeper Roofing, we most often recommend removing the old roof before putting on the new one. When it comes to the quality and functionality of your roof, what you can’t see is just as important as what you can see.
Many times when we pull the shingles off of a roof in disrepair we find rotted plywood and rotted wood decking. Without tearing the old roof off, you may never discover these structural issues. Even if the plywood is not rotted, it may be raised or loose. If the old roof is removed, those areas can be repaired before the new roof is installed.
Problems with recovering an old roof
If you do recover an old roof, and you leave areas of rotted plywood unrepaired, not only will the structure of the roof be compromised, the new roof fasteners will come loose over time. This could cause major maintenance issues and shorten the lifespan of your roof.
Benefits of recovering an old roof
By installing your new roof over the top of your old one, you will likely save a little bit of money on the front end. However, those savings will rarely exceed 15% of the cost of the roofing cost. Theoretically, recovering an old roof would not compromise the new roof’s functionality or longevity.
If you’re thinking about going this route, you’ll definitely want to get inside the attic and take a look at every area of wood decking in the roof structure. If you can’t get in the attic to see that, it’s better to err on the side of caution, and tear the old roof off.