[chinfan12]

I am preparing an exterior wall (concrete panels) which has been covered in paint but had no/inadequate preparation. I have managed to remove most of the paint but some has adhered well. I now propose to apply a fungicidal wash, followed by a stabilising solution prior to exterior paint.
Can I apply paint to cover the areas that have cleaned up as far as the adhered paint and then go over the whole panel with two more coats of exterior paint, or must I try to get all of the paint off first? If so, any suggestions on how to do this please? Any advice would be appreciated.

 

[jsheridan]

Chinfan, as long as the paint is adhered to the surface, there's no sense removing it only to apply more. In the absence of moisture coming through the back/underside, and with the original paint applied to a stable surface, concrete holds paint pretty well. After washing, be sure to allow ample drying time, it holds moisture well also. I'm not sure how long, but two good drying days should do. Also be sure to check whether your finish is spec'd to go straight over bare concrete, some are and others aren't. Or, if you think you may have trouble, consider using SW Loxon concrete primer. It may not be necessary, but it'll never hurt (unless you're using Drylock).