Typically we do not remove shingles and install a new roof on the existing structure. There are a few reasons for this. Firstly, the existing roof will work as an additional barrier. Secondly, removing shingles usually results in leaving holes in the underlying plywood that tends to make the plywood loose and weaker as a structural support. Thirdly, when shingles are removed, there are a lot of nails that come off. Although our installers always do a diligent job in cleaning up the site after the job is finished, we can’t guarantee that a few nails will not get lost on your driveway or backyard and potentially pose a safety hazard. Fourthly, our cost of removing shingles is approximately $1/per sq. ft., depending on the complexity of the roof. The customer always has the choice to remove the shingles off their roof if they desire. However, if there is no real need to remove the shingles roof before metal roof installation, then we think that there is no need for you to pay those extra charges.
Nevertheless, there are two scenarios when we will insist that the shingles do need to be removed. The first is when the roof is over 60-70 years old and will not be able to support the new metal roof and all its accessories. The second is when your current roof has more than 2-3 layers of shingles and the installation of the metal roof might cause structural sagging. In both of these cases we would need to remove at least one layer of shingles and potentially work on improving the structural support. This additional work is always quoted as part of our official estimate and we do not begin metal roof installation unless we are 100% certain that your house can support it.