Steps to Painting Cement Block Walls
Preparing the Wall before Starting Painting
Cement block walls present a drab look if they are allowed to remain unpainted, so make your cement block wall more appealing to look at by giving it a few coats of paint.
Painting cement block walls can only start once the cleaning process has been completed. This is because dust and dirt does adhere to block walls, more so if the texture is rough. If the wall has been painted earlier, there would be the additional task of removing the old paint and peeling it off completely. New cement block walls are also likely to have efflorescence, which is formed by salts from within the concrete coming out on the surface with the dampness that is inside the block wall. Acidic masonry cleaners are available, which can help the cleaning process and especially remove the efflorescence. If the wall is on the exterior, it is best cleaned by pressure washing with water into which the cleaner has been added. While pressure washing, pressures used should not be so high as to damage the surface of the wall. A pressure of 2500 psi, with a spray held 12 inches from the surface, should do the job properly. New walls are better served with lower pressures. Washing should be done from top to bottom. For interior walls, pressure washing may not be possible and the use of a brush and adequate water, with the cleaner mixed in it, is suggested.
Now that the wall surface has been cleaned, you need to inspect it thoroughly and repair any damage to the wall. It is preferable to use premixed acrylic mortar for the repairs. If you mix your own mortar, you may have to wait an additional couple of days for the mortar to set. You can also use a sealer to seal the wall if the surface appears too chalky.
Priming and Sealing the Cement Block Wall
Now that you have cleaned the wall and repaired it, you can proceed to priming the surface. Primers function as fillers for pores and also neutralize the high PH inherent in cement. A number of primers that can suit cement block walls are available, one of them being Acrylic Block Fill. You can also get primer with oil base formulas for use for oil painted surfaces. Primer coverage is 200 square feet per gallon on smooth walls and about half that on rough walls.
Once the wall has been primed, you would need to seal and caulk any gaps that are more than a sixteenth of an inch. This will prevent water from entering through these cracks. An elastomeric or polyurethane compound can be used. They can be loaded in caulking guns and squeezed into the cracks. Wider cracks or expansion joints may need foam backer rods to support the caulk. You are quite likely to find cracks around windows and doors where you would need to be extra careful.
Painting Cement Block Walls
While spraying of paint is quite common, the best way of painting interior cement block walls is using the brush and roller techniques. It may take longer, but you are more in control of the quality of work.
You can use elastomeric paint for exterior wall, though paint that is a hundred percent acrylic can do the job just as well. If you are painting interior walls you would need to decide the décor you want before selecting the paint. There are many types of paints available from oil, enamel, acrylic and others that could give you all the variety you need. Paints with a gloss are easier to clean and maintain. You may need to apply at least two coats of paint to do a proper job. Paint that is sprayed on needs to be back-rolled immediately.
So get down to painting that cement block wall, by first preparing it to receive the paint and then by painting on your choice of colors.