How to Fix Concrete Block Paint Failure
One of the most common building materials on the market is Concrete Block. It's used extremely often on commercial and industrial buildings. Though it is great material, it is not immune to paint failure. A number of factors can cause concrete block paint failure, so here are some things to look for.
Inspect concrete block exterior (and interior) for cracks. Look for moisture. If ignored, cracks and moisture will not only create more paint failure, but affect the building's structure. Not good.
It's important to note that some cracks can be caused by foundation settlement. This is okay, but the cracks should still be inspected and patched so as to prevent moisture intrusion. Cracks can also be caused by thermal expansion (heat) and bad structural support. If it's the latter, the problem extends beyond paint and will require an engineer's inspection. Cracks can shift or remain static. If you see diagonal or stair-stepped cracks, then you're seeing settlement cracks, which appear at the base of the concrete block wall.
Mortar joints—the spaces in between concrete blocks—should also be inspected, as moisture can deteriorate this material. What causes mortar joint failure? Poorly-mixed mortar and the freeze/thaw cycle. This is especially a problem after harsh Midwest winters. If the mortar joints are stable but need repair, a painter can provide a service called tuck-pointing or repointing. This involves re-application of fresh mortar to the mortar joints. Also look for holes, gouges, and scrapes, and have them sealed with masonry material.
Once all of this is done, it's time to paint.
Concrete block comes in smooth or textured block. Smooth requires far less paint than textured block ("split-face"). Why? Well, textured block is rough, porous and looks a bit like gravel. The paint must be worked into that porous surface in order to properly seal the block. Otherwise, again, you're asking for paint failure. Textured block requires double the amount of primer and paint than smooth concrete block. That said, commercial and industrial companies like it, so it's a very popular choice.
Acrylic paints work really well on concrete block. Paint is typically sprayed on and back-rolled and/or brushed. This, of course, is to ensure the pores are properly filled.