As long as it s done right and under the right conditions installing new shingles over old ones can last as long and look just as good as a complete re roof.
Installing new roof over old.
Installing a new roof over shingles takes less time than tearing off the old roof.
If conditions are right new shingles laid over old shingles can be just as attractive and durable as shingles laid on bare sheathing.
Leave the old valley flashing in place and install new over it.
Manufacturers will still warranty the roof for the same amount of time as a re roof as long as it s done by a qualified installer.
Has the same manufacturer s warranty.
Installing a new roof over an existing one also called a layover or nailover is often possible although not always the best option.
Installation is easier than for a tear off job because you can use the existing shingles as guides for laying the new ones.
To level out an existing asphalt shingle roof rip down reduce the height of two courses of shingles as shown in the drawing below.
A properly installed layover roof can look and function as well.
Installing new roof shingles over old effectively doubles the weight of the roofing so you have to make sure your roof structure can handle the extra load.
Looks just as good and lasts as long.