http://www.thisoldhouse.com/toh/arti...8584-3,00.html -"To cover asbestos siding, install insulation board and vinyl siding over the shingles. Make sure screws penetrate at least 3/4 inch into the wall studs."
- "Some contractors believe that asbestos poses no problem as long as it is not moved. Once moved - or in this case, removed - fibers become airborne and that's what causes the health risk. State agencies, however, have strict guidelines for contractors, so don't take this project lightly. If it were my home, I'd probably choose to have it covered first with rigid foam insulation to provide a level surface and then have the siding installed over that. Removing and disposing of the asbestos definitely will cost more. There are some concerns with covering it, however. One is the difficulty in nailing through asbestos siding. It's a hard, brittle material, and normal siding nails can bend. The contractor you choose should be experienced in installing vinyl over asbestos. There are those who believe that pounding on asbestos shingles and driving nails into them also can disturb those pesky fibers. Whatever decision you make, be sure your contractor is certified by the proper state agency."
Siding Over Asbestos
We live in an old Victorian house with asbestos siding on it. We want to put vinyl siding on it, but we need to know if it is necessary to remove the asbestos siding first. Siding contractors say they can apply the vinyl over the asbestos, but one contractor warned us that the asbestos siding will crack when the vinyl siding is nailed on top of it, and that pieces of broken asbestos would fall down and accumulate, causing bulges in some areas of the vinyl siding.
I discussed your situation with the Vinyl Siding Institute, which said that it recommends not disturbing the asbestos shingles. The best practice would be to apply sheathing over the existing asbestos siding and then apply vinyl siding over the top of the sheathing. The sheathing will serve to flatten the walls and will contain any broken asbestos shingles. The vinyl siding should be applied using nails that are long enough to penetrate the sheathing, the asbestos shingles, the sheathing below the shingles and the wall studs.
For information on installing vinyl siding, the Institute offers the manual Rigid Vinyl Siding–Application Instructions. It is item BG 105 and can be ordered from The Society of the Plastics Industry Inc., P.O. Box 753, Waldorf, MD 20604; 800-541-0736."