In dealing with houses with asbestos siding, the local Habitat for Humanity found it best to just remove the asbestos siding and then install rigid foam and vinyl siding.

Asbestos containing shingle siding is extremely hard to begin with, age increases that hardness.

The nails used to install it were most probably drilled at the factory or onsite. I can guarantee the existing siding will break when nailed from experience.

Since you have extensive water damage from improperly flashed windows that will require removal of the siding down to the water damaged sheathing anyway. It's a false economy that would have you think that not going ahead and removing it all would actually be easier and cheaper to deal with when residing. You MUST remove the water damaged portions and replace them.

In fact, it more labor (more $$) to try to make up the thickness difference between the existing siding and the areas around the windows that would need the siding removed and sheathing replaced in order to properly be flashed. That is assuming that there is a proper drainage plane of housewrap or roofing felt behind the existing siding. That's assuming a lot for a home of the era that is sided with asbestos.

Most likely, that damage from the ongoing water penetration has destroyed most of the sheathing and insulation. It's also likely that there isn't a proper drainage plane in existence to begin with. That will need to be corrected in order for new siding to function properly. That means removing all of the existing siding.

Back to square one. It's always cheaper to do the project correctly in the long run.

Asbestos cement panels should not be penetrated. Driving nails through is a definite NO-NO!

Stop this contractor before they contaminate your property with asbestos dust!

The old asbestos cement material had pilot holes drilled befroe fastening. Asbestos is too brittle to nail through directly. The workers were exposed to occupational asbestos hazards because they did not know the dust created during drilling and cutting was dangerous.

what handymac said.

nailing through asbestos siding will cause it to
break. take it off. re-sell it.

put an air barrier/vapor barrier on walls after
removing siding. vinyl siding does nothing
to stop air leakage into walls.

if you have water damage as hollysprings says
(must be another thread??) then address those
issues by replacing damage & properly flashing
the windows. otherwise it will cost more to
fix it later.

as asbestos shingles are OUTSIDE, you aren't
contaminating anything. you can't get much
more dillution than the great outdoors.

best of luck.

"as asbestos shingles are OUTSIDE, you aren't
contaminating anything. you can't get much
more dillution than the great outdoors."

This is NOT TRUE. Transite siding and roofing are a Regulated Asbestos Containing Material (RACM). Contamination is a big concern, outdoors or indoors. Here are the proper removal procedures for transite siding and roofing:

1. Place 6-mil polyethylene sheeting under the removal area to collect any debris.
2. The material MUST be misted and kept damp throughout the removal/bagging process.
3. Removed materials should be immediately placed in a 6-mil (or greater strength) plastic bag.
4. Avoid breaking up roofing or siding. Work slowly to keep breakage to a minimum.
5. Lower materials to the ground, keeping panels or shingles intact. Do not drop or throw them.
6. "Double-bag" all waste (roofing, siding, personal protective equipment, tools and any other items that have come in contact with asbestos materials) in 6-mil (or greater strength) plastic bags.
7. All waste must be disposed at an appropriate landfill that accepts asbestos-containing materials. Call the landfill prior to transporting the waste. The type of waste accepted at landfills differs and is subject to change.

The HfH chapter for which I volunteered used volunteers with long sleeved shirts, dust masks and gloves to remove asbestos shingles. With due care, this is a safe procedure. The plastic on the ground and the double bagging are necessary, as well as a applicable dumpster.

Asbestos is dangerous because of the tiny fibers that make up the mineral asbestos. Those fibers are light enough to be easily airborne and inhaled. The fibers are mineral, so they never change, which causes the body's defenses to try and combat them.

Airborne asbestos is called friable asbestos. The asbestos in siding is combined with adhesives which greatly reduce the friability factor. Making it much less dangerous with proper precautions.

both of you are absolutely correct.
my reply was totally incorrect.

thanks to both aiden & handymac
for catching my error.

best of luck.