The best life will come from removing all the old layers down to roof boards or sheathing and then laying down the new roof on a well repaired flat surface.
Three layers of shingles on roof.
Bring the ridge edges together with a ridge capping layer.
You ll need longer nails for this part as you re driving through more layers of shingles.
According to the international existing building code homes can be re roofed one time by applying a second layer of roof shingles over the existing one but after that application begins to wear.
Your three layer roof is definitely a potential structural concern and homeowners insurance companies might consider three layers of roof shingles.
Most cities and towns allow a maximum of two layers of shingles says chad muth president of muth company roofing in westerville ohio.
Should be obvious from the street.
You can either use special shingles called ridge shingles or cut a number of regular shingles into 3 tabbed equal pieces and bend each so they fit snugly on the roof peak and nail them into place.
But contractors who spoke with angie s list say best practices call for stripping the roof down to the wood deck to inspect it before installing a new roof.
Layers of shingles on top of each other shorten the life of the roof due to the newest layer sitting on an uneven lower surfaces.
If there are really three layers of shingles it probably is far from a hidden issue.
Unless the roof caves in.
Now you just have to decide whether to remove the existing roof shingles or recover the roof.