The phrase "new roof installation" doesn't just encompass a single thing. There are three things that may be meant, so it's important to know the most common roof replacement methods.
The least time-consuming and most cost-effective option for a new roof installation is re-roofing. The old shingles are left on the roof, and new shingles are simply installed over the top. Since there is no teardown or old shingle disposal, the new roof takes half the time to install and there are fewer labor and dump costs, as well.
Re-roofing is only an option if the old roof has no major leaks or structural damage. Small leaks can be repaired, but larger issues will compromise the new shingles. A full inspection will be completed to make sure the roof decking and underlying structure are still in good condition prior to roof installation. Applying new shingles over the old can only be done once, so if your last roof installation was a re-roof, you won't have that option for your next new roof installation.
The most common type of new roof installation is a shingle replacement. It's so common, it is typically what most people think of when they realize they need a new roof.
In a shingle replacement, the old shingles and the underlayment — also called roofing felt or tar paper — are pulled off the roof in a process called teardown. The plywood decking is left in place, although some small repairs may be necessary if cracks or small holes have occurred. Finally, fresh underlayment is put down followed by a fresh layer of shingles. New flashing, vent boots, and sealants are the last thing installed. Your roofer may also replace some roofing vents if they are aged or damaged.
The most time-consuming and expensive type of new roof installation is the full replacement. The good news is that this is not necessary every time you need a new roof. Full replacements are only done when there is damage to the roof decking or the underlying structure, such as the roof trusses. This type of damage occurs from years of neglect that have caused major water damage, or from outside damage such as tree fall or major storms.
In a full replacement, your roofer removes the shingles as well as the roof decking. Trusses and joists will be assessed for any necessary repairs or replacements. New decking is then put on, followed by underlayment, shingles, and flashing seals.
Contact a roofing installer for more roofing infrmation.