Asphalt roof replacement - remove the old roof (only 1) first?

You are allowed to put three layers on a roof before having to strip off the old and start over, however if any large areas have become dislodged and the sub roof comprimised you may be better replacing it all. By your description it sounds like you would be safe to go over the old.    C7   

You are allowed to put three layers on a roof before having to strip off the old and start over, however if any large areas have become dislodged and the sub roof comprimised you may be better replacing it all. By your description it sounds like you would be safe to go over the old.    C7   

  In N.J. you are allowed to go over only one existing roof, GA i'm not sure.

Depends on how old the roof is under 10 years old it would be fairly easy to remove damaged shingles with new ones. How big is the damaged area if only a shingle here or there the replacement shingles won't stand out to bad. If the roof is over ten years and the granurals are missing I would replace that section at least

Depends if you want to check out the decking underneath the felt paper which is underneath the shingles.  I'm a project manager for a roofing company and have found out that sometimes you have a messed up piece of decking that has leaked at one time or another, We @fixall like to strip back the roof/ felt  all the way to the decking to inspect the decking to make sure everything is still good.  You may also want to check your insurance policy it doesn't only cover hail damage but has provisions for wind damage as well.  I know we have offices in GA I'm located in Dallas/ Ft Worth.

Why would you not go back to the deck when you get to inspect the decking, new felt and new shingles, why stress the roof out with several layers of shingled weight.  A good site to go to is www.fixallroofing.com check it out and see for yourself.

Good Luck