Old Rubber Roof Torch Down - Should you Remove it or Install a New Rubber Roof over the existing?
Channel: Flat Roof Doctor
Date: 01/06/2021

The question always remains, what is the best thing to do? Should you remove an existing roof or should you install a new roof over the old one?
I have been installing Torch Down Rubber Roofs for over 35 years. In all my roofing years I have stripped a few roofs. It is almost never necessary to remove an existing flat roof.
here is a video where we install a Torch Down roof over gravel -https://www.youtube.com/watch?v=RpCzsQ7HUog
https://www.youtube.com/watch?v=tYkxBnwlR7Q&t=503s
In this video, we installing a Torch Down over an existing Torch Down -https://www.youtube.com/watch?v=2-QNrGrbFgo
I know what the law says. After 2 layers you should strip everything off. This law was not meant for flat roofs. It is meant for Shingle roofs that are nailed down. Shingles get spongy after 2 layers and the nails start to pull through.
My rule of thumb is, If an existing roof surface is in a relatively good condition, meaning no rotten substrate, where I can feel it as I walk on the surface, then there is no need to strip it.
So many flat roofs get destroyed that could have been used for the better.
Here is information on the materials we use for Torch Down - https://www.firestonebpco.com/content/dam/fsbp/migrated-document/ca/en/16/169958.pdf
We also use Karnak 81 Trowel for all the transition areas like on drip edges and around vent pipes - https://www.karnakcorp.com/product/81-modified-bitumen-adhesive

Indicators on a rubber roof that can help you decide the condition of the roof:

0:00 To strip an existing roof or to go over?
0:25 What to look for on a commercial roof
0:39 Determining what type of roof you have
1:00 Sign of Bubbles or air pockets 
1:17 Tar is a sign of trouble
1:54 Tar on the perimeter edging
2:45 Why no reason to strip a Rubber Roof
3:18 Melting the New Rubber to existing
3:58 Cutting through 2 layers of roof
6:35 Patching the Roof with a Torch