When looking to purchase a new roof for their home, many homeowners debate laying new shingles over the existing shingles or just start fresh by tearing off the old shingles. Usually homeowners think about laying over to save some money – but is it worth the saved bucks?
Most cases – no. Its worth tearing off your shingles for the following reasons:
Inspect Condition of Roof Decking
Without tearing the shingles off and actually seeing the roof deck, one can only speculate the condition of the OSB. Obviously, if sections of your roof are rather soft to walk on the wood is bad and will need replaced. However, you can have smaller sections of wood rot and not know it until the shingles are torn off. The images below were actually caused from a window leaking long term. If the homeowner would have selected a layover, the source of the leak would have persisted and continued to cause damaged to the siding wall and the roofing structure
Many shingle manufacturers have rather poor warranties for roofs that have been laid over. Best case scenario you will get a 10 year limited life warranty – it will be pro-rated. If the shingle fails within the first year after your roof lay over, you will have to pay some money out of pocket. The best thing about a Carlson Exteriors roof replacement is the roof warranty. Any roof we replace will get a 50 year, non prorated warranty that is transferrable one time. It actually increases with inflation so you don’t have to pay anything out of pocket! Woohoo!
Overall Roof Appearance
If your old shingles have warping or curled up edges, the new shingles that you lay over will take on the look of the old shingles. The new shingles may look wrinkly or bumpy. The new roof will look terrible from day one.
Shortened Roof Life
If a new roof is laid over, it will have a shorter roof life. The shorter lifespan is due to a couple reasons. First, not nailing directly into the roof decking can lower your roof’s resistance to high winds. The nails might not be driven as deeply or as securely into the plywood as they should be. On the other hand, some nails may be overdriven thanks to the old shingles “cushion” . When nails are overdriven, it can pierce directly through the new shingle and not provide any security at all. Some home insurances provide better rates if your shingles are nailed directly into the OSB. Secondly, the moisture trapped between the two layers of shingles will increase the speed of asphalt deterioration. The second layer of shingles will increase heat and moisture retention, especially if your roof is not ventilated properly.
Too Much Weight
If you already have two layers of shingles on your home, city code prohibits another layover. This is because of the unnecessary weight each layer of shingles add to your home. If you are outside of city limits and are not required to obey city codes, be mindful of how much weight and stress you add to your home’s structure
Carlson Exteriors always tears off the existing shingles for these reasons. The money that homeowners would “save” by not tearing off old shingles is not worth it. A layover roof can be deemed more expensive due to poorer roof warranty, possibility of more leaks, and the damage that could be done to home’s structure. In this case, the cons outweigh the pros.