Whether or not to re-shingle a roof is a question that plagues every homeowner when they realize the life of their shingles is about to expire. Either option offers both negatives and positives that the homeowner must consider when making a decision. The majority of homeowners know that putting new shingles over old is an option, but are unsure if the results will be as good, and if it is safe to do so. As long as certain precautions are taken, overlapping can be just as safe as re-shingling.
Replacing or Overlapping: That Is The Question
Re-shingling a roof involves hiring a roofing contractor to remove the old shingles and install new shingles. Usually, the contractor inspects the wood under the shingles as well as any protrusions through the roof such as dormers or ventilation. According to International Residential Code (R907.3), you can only put new shingles on top of old shingles if you have less than two layers of shingles already on the roof.
The biggest reason why building codes prevent you from installing more than two layers of shingles is because of the weight. While just one shingle is not very heavy, an entire roof of shingles can weigh as much as an SUV. According to Bob Vila, a roof covered with 1,500 square feet of shingles is the equivalent of having a two-ton SUV parked on top of your home.
Pros vs. Cons: That Is The Dilemma
Choosing to overlap is beneficial if you have less than two layers of shingles currently on your home as you do not have to spend the time or the money having the previous shingles removed. Having the old shingles removed can be equally beneficial as it is a great time to have the roof inspected to ensure there isn't any deteriorated wood or leaks underneath the shingles.
The biggest downside to installing new shingles over your old shingles is the additional weight on your roof. If the wood underneath the first layer of shingles is damaged, it could cause your entire roof to collapse under the weight. It is a common misconception that the additional layer of shingles will just add insulation. The extra layer of shingles will absorb heat and force your air conditioner to work harder to keep your home cool and comfortable.
As you can see, placing new shingles on top of existing shingles is only a bad option if the structure of your roof is weak or you already have two layers of shingles on top of your home. Contact the best roofing companies in your area for more information.