How to Cover Asbestos Siding on a Home Safely

You cannot treat asbestos like a normal building material, so you must prepare the area beforehand. Other than removing all items close to the wall and making sure all your windows are shut and sealed, you will need to make sure there are no fans that would pull any disturbed asbestos fibers into the house or ventilation system. You usually would powerwash a wall before doing work, but in this case it is not advised.

Asbestos siding is usually quite brittle, especially if it has been exposed to harsh elements over time, which most siding has. You should go around the house making sure that no tiles are brittle or falling apart before starting this project. An easy way to check for brittle tiles is to tap them lightly with a screwdriver or hammer. If a large majority of the tiles crack and disintegrate, you may have to remove the asbestos siding entirely. 

A foam board layer will be the first layer that goes on top of the existing siding. It is put in place mostly for insulation, but also to lessen the amount of noise you hear in the house. These foam boards come in large sheets and can be laid over existing siding as long as it is uniform. Foam board is generally installed with nails, and it is much faster and more precise to use a nail gun than hammer in nails by hand. 

If the existing siding is in good shape but not uniform, you may want to consider adding a layer of furring strips at this stage, as well as after the moisture barrier. These strips simply make it easier to attach the foam board to the existing asbestos siding.

Once your foam board is installed, you need to add a moisture barrier to protect the foam and the siding behind it. A moisture barrier also doubles as an asbestos barrier, helping to seal in any fibers that became airborne while installing the foam board or checking the siding.

Furring strips are long, thin strips of wood used to create a flat surface on which to hang things like drywall, foam boards, or siding. They also exist to create a gap in between the moisture barrier and the outer protective layer. This allows for better insulation and moisture control. Installing furring strips between a foam board and existing siding is often optional (it may depend on local rules), but installing furring strips between the moisture barrier and the new siding is a requirement. 

Whichever siding you choose is up to you, but probably the most common siding put on top of asbestos is vinyl. Vinyl is low-cost, easy to install, and resistant to the elements. It provides a decent seal that helps protect against asbestos leaking out, but it is never going to be as good as removing the asbestos entirely.