When it comes to roof replacement, you have two options to pick from. You can either rip the old roof off your home and install all brand new material, or you can install a new roofing layer right over the old one. Here are some thing to consider when you add new shingles without removing the old ones.
You MIght Not Be Able To Add Another Layer
The first thing you want to find out when you are deciding to add another roofing layer is if you're allowed to do it. You'll need to check the building code for your city and find out what the rules are regarding roof layers. It's possible that you are only restricted to having two layers on a roof, and you won't be allowed to add a third layer. This forces you to remove the old material to install the new shingles.
Other considerations that go into the building code is the type of materials you use, with some being allowed to be overlaid and others are not. Your roof's pitch can also play a big role, with a very steep roof not allowing for additional layers of roofing material.
You Can't Fix Defects With Your Roof
One of the advantages of ripping off the old roof is that it gives you the chance to start over. You can identify problems with your roof that need to be fixed, and then repair them before the new roofing material is installed. If you install new materials on top of the existing roof, you won't be able to find and repair those problems. They'll still be there for the life of the second layer of roofing material, and potentially get worse and lead to a bigger repair down the road. Some common problems include rotting wood that causes the underlying structure to become weak, and mold growth underneath the shingles.
You'll Deal With New Roof Problems
When you add layers onto a roof, know that it will be susceptible to problems that you didn't have before. The big issue you'll run into during the winter is ice dams. Moisture gets trapped between the two layers of roofing material, which freezes and expands. This is a new issue that can cause damage that you never had to deal with before.
Reach out to a residential roofing contractor for more information about adding a second layer to your roof.