I am planning on reroofing with architectural style fiberglass shingles on a 3/12 pitch. The existing roofing is tar/gravel. I tried to remove a section of this, unfortunately it was installed with the first layer of felt adhered to the sheathing with
tar. Needless to say, it is very difficult to remove. I would like to know if I can install shingles over this, with any special precautions I should take, or for any advice on how to remove the existing roof. Thank you.