Should I paint a block wall that has never been painted?

Think about it first. Bare block needs very little maintenance, and once it is painted it will need repainting from then on, because removing paint from masonry is slow and difficult. Painting is worth it when the wall looks stained or patched, or when you want it to match the house. It is a decision that is hard to undo.

Slump stone is a concrete block made to sag slightly before it sets, so each block has rounded, irregular edges that look like adobe. It is very common on garden walls across San Diego County, especially in East County. Its deep, uneven joints and texture take far more paint and care than flat block.

Why does a painted block wall peel at the bottom?

Usually because of water at the base. Sprinklers soak the lower courses, soil piled against the wall keeps it damp, and water rising through the block pushes salts and moisture behind the paint. Fixing irrigation and keeping soil off the wall face matter as much as the paint itself.

Painting Block and Slump Stone Walls

Q: Can I paint my side of a wall shared with a neighbor?

Usually your side is yours to paint, but the cap and the ends are visible to both of you, and a property-line wall may be jointly owned. Talk to your neighbor before work starts, agree on what is being painted, and arrange access if both sides are to be done. In HOA communities, perimeter walls often belong to the association.

Block and slump stone garden walls can be painted to look fresh for years, but masonry is porous, alkaline and rough, so it needs more preparation than stucco. The wall is washed, any efflorescence is dealt with at its source, pores are filled with a masonry primer or block filler, and the paint is worked into every joint and hollow. A shared wall needs the neighbor's agreement first.

Drive through Santee, El Cajon or Spring Valley and you will see mile after mile of masonry garden walls: smooth gray block, split-face block, and the rounded, adobe-like slump stone that has gone up on so many San Diego lots for decades. Some are bare, some were painted long ago and are peeling, and some are stuccoed over. All of them are part of how a property looks from the street.

Painting them is a different job from painting the house, and it is worth knowing why before you decide.

What kind of wall do you have?

Standard concrete block. Flat faces, straight mortar joints. Porous, with a slightly open surface texture.

Split-face block. Rough, broken-stone faces. More texture and more surface area to cover.

Slump stone. Block made to sag a little before it hardened, giving soft, uneven edges and deep, irregular joints. Attractive, and the most demanding of the three to paint well.

Stucco over block. Painted much like a stucco wall on the house, with the same attention to cracks.

Why masonry is not like stucco

It is thirsty. Bare block and mortar are full of tiny pores and pinholes. A coat of ordinary paint soaks in unevenly and leaves pinholes showing through, so the surface needs filling and priming first.

It is alkaline. Concrete and mortar are naturally alkaline, strongly so when new. Paint labels say how long fresh masonry should cure before coating, and products for masonry are formulated to tolerate alkalinity. Sherwin-Williams, for example, recommends about 30 days of cure for new concrete, and allows its Loxon masonry primer on surfaces at least 7 days old with a pH below 13. A newly built wall waits until the label says it is ready.

It moves water. A freestanding wall is exposed on both faces and the top, and its base sits in the ground or a planter. Water gets in at the cap and the footing and travels through the block. That water carries salts to the surface as white efflorescence. What the white crust on block walls means.

It is rough. The texture, especially on slump stone, has to be fully covered, including the backs of every bump and the bottom of every joint.

Before painting: is it a good idea?

A bare block wall needs almost nothing from you for decades. Once it is painted, it needs repainting from time to time, because taking paint off masonry is slow and difficult. So painting is a commitment. It is the right choice when the wall is stained, patched, mismatched after repairs, or does not suit the house. It is worth a second thought when the wall looks fine as it is.

If the wall is already painted and peeling, the question is answered: it needs proper preparation and repainting.

How a block or slump stone wall is painted

Clear the base. Soil, mulch and plants are pulled back from the wall so the bottom courses can be reached and dried.
Wash. Dirt, mildew, loose paint and any efflorescence are cleaned off. Efflorescence that keeps coming back points to a water source that has to be dealt with first.
Scrape and repair. Peeling paint is scraped back. Cracked mortar joints and broken corners are repaired, and the repairs are left to cure.
Fill and prime. A masonry primer or block filler seals the pores and evens out the surface. Both Dunn-Edwards and Sherwin-Williams make products in this category; Sherwin-Williams Loxon is one example of a masonry line.
Paint, working into the texture. On slump stone and split-face block, paint is usually sprayed or rolled with a thick nap and then back-rolled or brushed into every hollow and joint, so nothing is left bare. Two coats are typical.
Finish the cap. The top of the wall takes the most sun and rain. It gets full coverage, and loose cap blocks or open joints on top are sealed.

The sprinkler problem

On almost every painted garden wall that peels, the worst failure is in the bottom few courses, where sprinklers hit the wall every day. No paint lasts long under that. Adjusting or redirecting the heads so they water the plants rather than the wall is one of the most useful things a homeowner can do for a painted wall.

Shared walls, neighbors and HOAs

Many garden walls sit on a property line. Your face is usually yours to paint, but the cap and the end pillars are visible from both sides, and the wall may be jointly owned. Talk to your neighbor before work starts, agree on what is being painted and in what color, and arrange access if both faces are to be done. In master-planned communities, perimeter walls along streets and open space usually belong to the HOA, and painting them is the association’s decision.

Color

A wall painted to match the house body ties the lot together. A slightly darker shade makes the wall recede behind planting. Light colors on a long west-facing wall in El Cajon or Santee reflect a lot of glare into the garden, which is worth seeing on a sample first. Flat and low-sheen finishes suit masonry best, because they hide the irregular surface.

Getting the wall done

Garden walls are often an afterthought in a house repaint, and they can take more time than people expect, especially slump stone. At the estimate, Ebenezer can walk your walls with you, look at where water is getting in, and tell you plainly whether painting is the right call for each one. More on exterior painting, or on homes in Santee and El Cajon.

If your garden walls are peeling, patchy or just do not match the house any more, ask for a free estimate and talk through the options with him.