You can absolutely tile over old asbestos tile and in many cases it’s the best course of action as it doesn’t disturb the contaminated material or send dangerous fibers into the air.
The fancy term is “encapsulation” and it can be used with all types of asbestos, but most often is seen when vinyl siding is installed over old asbestos siding or carpet is put in over old asbestos flooring or tile.
It may seem at first that you’re simply covering up and hiding a problem but many experts and government agencies recommend this course of action. Asbestos is completely safe as long as it isn’t disturbed; it’s only when it is broken up, torn, or crushed that fibers are released which is when health risks for mesothelioma and other diseases become a danger.
Installing Carpet over Asbestos Tile
This is the most common situation for many homeowners who are dealing with older 9×9 or 12×12 asbestos tiles. While the old tiles can be removed — and even safely removed by the homeowner with proper precautions and equipment — it’s usually not worth the risk, especially if you plan on installing carpet anyway.
The process is very simple, with the only extra step ensuring you have a stable, level surface to install the carpet pad and carpet on. Replace any missing tiles with similarly-sized new ones about the same thickness (the color and style doesn’t matter since they’ll be covered) and fill any gaps or cracks with leveling compound before installing the new pad or carpet.
No other specialized prep work or treatment is necessary. Installing vinyl flooring is a similar process.
Installing Ceramic or Porcelain Tile over Asbestos Tile
This is trickier as you can’t simply slap mortar down on top of old asbestos tile, put down the new tile, and expect a good result. It’s not the asbestos that’s the issue but instead the slick surface that will cause your tile job to fail.
You’ll need to first install Hardi-backer or an equivalent backerboard on top of the old flooring in order to have a good surface to tile on. Try to minimize the amount of screws or other fasteners you use to install the backerboard, mortaring it in place as much as possible and then screwing down the corners and midpoints of each piece.
Be sure to factor in the fact that this will inevitable raise the final height of the flooring when done and factor that in.
Installing Hardwoods over Asbestos Tile
This is probably the most difficult installation and one you should really consider before tackling. Leaving the old tile and flooring in place means you’ll often have a lot of difficulty in putting in hardwoods as you often won’t be working with a flat, stable surface (and you can’t tear it out as you normally wood to get a smooth, stable base).
Adding a new subfloor also often raises the height of the finished floor too high, especially in kitchens where the height of the floor and dishwashers come into play.
Due to the difficulties involved, carpet or vinyl is often a better choice than hardwoods as far as covering up old tile.