Q: What’s the best way to prepare the outside of an older building for paint? The walls are covered in asbestos siding that was probably installed during the mid-1950s. Is it safe to remove loose paint in the usual way, or do I have to do something different because of the asbestos?
A: Besides the need to create a good surface for painting asbestos siding, there are two other areas of concern. The first is the possible (and almost certain) presence of lead based paint on the siding, and the second is the asbestos in the siding itself.
Begin by analyzing a paint sample for lead content. You can find inexpensive test kits online. If the paint does contain lead-based (and at least a few layers probably do), then it needs to be removed with hand scrapers while keeping the surface wet. That is if you want to retain the old siding, that is. Workers will also have to wear HEPA-rated respirators and use disposable coveralls. This isn’t a big deal, you just need to use the right kind of gear. Paint chips must also be collected for proper disposal as toxic waste.
Another option is to blast the loose paint off with a pressure-washer, though this only makes sense if the paint is lead-free and harmless if a little remains on the ground. Some people would go with this option, but I’d be leery.
Regardless of what kind of paint you have, it’s crucial that you don’t clean the shingles using dry abrasive methods or heat. This would loosen asbestos fibers, causing a dusty health hazard. Every asbestos expert I’ve spoken to recently says that the form of asbestos used for wall shingles is not as harmful as other types, and that one safe option is to leave well enough alone. They recommend that leaving the old shingles on is a safe choice, though removal is a possibility, too. You’ll need to consult an asbestos expert to discuss removal and disposal.
When it comes to applying a long lasting coat of paint, start with a 100% acrylic exterior latex primer, followed by 100% exterior latex paint. Not all latex paint is 100% acrylic, so read the labels. Asbestos shingles hold paint very well when you use the right kind of coating.