When shingle wear and degradation becomes noticeable, most homeowners want to remedy the situation before the problem worsens and leaks and water infiltration problems can begin to occur. One approach that many homeowners consider to address this issue is the addition of a new layer of shingles directly on top of the existing ones.
Many consider this approach in an effort to save money on installation costs and eliminate the work involved in removing old shingles, as well as doing away with expensive landfill or disposal fees for the old shingles. While these benefits can certainly be appreciated, the installation of new shingles directly on top of the old ones can have serious drawbacks that must also be considered.
If you are a homeowner in need of a new roof and are considering the addition of a new layer of shingles instead of completely re-roofing the home, here are three things you must carefully consider.
Overlaying may not be allowed under existing building codes
Adding a new layer of shingles over an existing layer, a process referred to as overlaying by most roofing professionals, may be restricted under local building codes. In many areas, existing building codes may restrict overlaying to asphalt roofing shingles and place a limit of two layers for residential roofing. The actual pitch of the roof and the structure's ability to support the weight can also be a factor in how this building code is enforced.
Adding a new layer of shingles can hide serious roof defects
Another negative aspect of using the overlay process instead of installing a new roof is the fact that doing so can conceal serious roof defects. Weak or rotten areas of sheathing and general structural damage of the roof that would normally be discovered during a tear-off process can go undetected when adding a new layer of shingles. This can leave the roof more susceptible to wind damage and stress from snow loads and increase the costs and scope of future roofing repairs.
The overlaying process can make the roof more susceptible to ice dam formation
Ice dams are especially damaging to roofs with multiple layers of shingles. This happens because moisture is easily forced between the layers, where it freezes, expands, and causes damage. For this reason alone, homeowners who live in areas that experience severe winter weather may want to avoid using the overlay process.
To learn more about the best re-roofing options for your home and budget, discuss your particular roofing situation with a reputable roofing contractor in your area.Share