Painting Masonry
Also see:Let new masonry cure for at least 6 months before coating it with any sealers or paint. This will give the excess alkali salts time to leach from the portland cement. If not allowed to escape these salts will prevent paint from bonding to the surface.
Preping Masonry
Prep the surface to be painted by removing all loose material using a stiff brush like a nylon–bristled scrub brush to go over the surface. Treat efflorescence bubbling using the method described here. Hose the masonry down if possible. If you're inside and can't do that, use a shop vac to go over the surface to pickup any dust.
If the masonry has been painted before, scrape off any loose or peeling paint with a putty knife. Brush the peeling areas with a stiff brush and dust off the surface. Prime the spots with a coat or two of latex or masonry primer and let it dry completely before applying the new paint.
Applying Paint
Painting any masonry material is difficult when trying to get good coverage with the paint coat. Bare masonry is the toughest because it's so porous it sucks up every bit of moisture that comes in contact almost instantly and it will keep absorbing moisture until it is saturated. This can mean that a full roller of paint will not go very far and it requires many coats just to cover a few feet.
Tips for Easier Masonry Painting
To make painting masonry easier try a few tricks. First be sure you have a very thick roller. A nap of at least an inch will be needed to spread the paint into all the little pits and crevices in the masonry surface. When using latex paint, mist the masonry with water just before applying the paint to make it easier to spread. Plan to do two coats on bare masonry to catch all the missed spots rather than trying to cover every inch with the first coat. To improve coverage, a third coat will probably be necessary and will be essential to get a smooth, consistent coat on bare masonry.
