Painting concrete walls can result in a few problems if the concrete wall has not cured. If the concrete cannot adequately cure before it is painted, the paint will trap the excess moisture within the concrete and the paint can peel some of the cement as it peels itself. Painting the concrete wall can also cause the plaster to not receive the water cure that it needs.
Cracks in the Wall
Before priming the wall, cracks in the concrete should be filled with a material that can withstand weather effects. If the wall plaster has a texture, then sealant should be of a matching texture. If it is not, bands of smooth surface can be seen through every coat of paint in a different contrast.
If primer and paint is applied, it needs to be applied across the whole surface in order to have the best results. Once the primer has been applied and allowed to cure, the finish coat needs to be laid on in several thick coats. If not, the uniform color will not be attained and you will not achieve the look that is desired. Some projects do not have primer applied before the paint. Other projects may have had paint thinned so much that the coat is not even effective. This makes the wall look like it did not receive adequate coating.
In order to get the bond desired, the right primer will need to be applied to new concrete walls. This will prevent paint delamination also. There are some paints and primers in particular that need to be used together. Although cement plaster and concrete should have a coat of primer before the paint is applied, painters do not always prime concrete and plaster.
Delamination is the process of paint peeling from a new concrete surface or cement plaster. Paint will delaminate from concrete just as it does from wood and metal. This is why the concrete wall needs to be well prepared and all application procedures need to be followed. Moisture from rain or from the concrete not curing will release from the concrete and cause cleaving.
Over Brushing the Paint
If a painter applies paint to the brown coat on cement plaster, the paint will serve as a bond breaker causing delamination. Plaster behind a coat of paint will turn soft if paint is not allowed to cure. Paint will keep the water from evaporating properly. Concrete walls need to be prepped and primed. Paint needs to be thick and not diluted.