Most foundation walls are made of the same block as discussed, but there are some other things to consider. For one foundation, walls encounter the ground. The decision to paint your foundation wall is a permanent one. Once you’ve decided to do it, changing your mind about how it looks is a lot harder to fix. Blocks being porous take every bit of the paint you apply. Even if you use a chemical stripper, you’ll never completely remove all the paint from the block leaving it looking, well, poor. In a great deal of homes, the foundation is built from blocks of hand cut sandstone, which creates a new problem. It being sand, it has a tendency to always flake off which doesn’t make for a sound painting surface.
The solution often times is to treat the stone with a water repellent before priming. Doing this gives a little more cohesion to the surface allowing for a better bond with other materials. The next question before starting any painting or priming is how far down to the ground do you paint? This is tricky because between rain, freezing, thawing, and drought, the level of the ground around your house is always changing. What I like to do is remove about an inch or so down on the wall, do the finishing work and back fill to the paint. If your home is newer, you may find a tar line on the block. This tar was applied to the block for waterproofing purposes. You may paint to this line, but if you cross it with paint, the tar will bleed through. Often times the block or stone will need mortar added to the joints before painting. Remember to wear the proper safety gear to protect yourself from the active ingredients of the mix and don’t mix up more than you can use in a short time. Follow the time limits suggested on the mortar mix container before painting. If the moisture is not allowed time to cure, the mortar will be “hot”, and the paint will peel off. After the prep and repairs are done, simply paint the wall with a quality latex primer and two coats of a quality latex paint.