Stucco Repair and Coating

Sorting the Cracks First

Every stucco job here begins with a walk round every elevation, marking cracks and putting each one into one of three groups. That sounds fussy for a paint job. It is the difference between a coating that lasts and one that splits back open in a season, so it is where we start.

Shrinkage cracking is the fine wandering stuff, thinner than the edge of a credit card, usually spread across a whole panel in something like a map pattern. Cement plaster shrinks as it cures and keeps moving with heat afterwards, so on the 1920s and 1930s bungalows around Belmont Heights and Rose Park this is simply what an old wall looks like. It is cosmetic. It is also exactly what a flexible coating is designed to bridge.

Stress cracking is a single straight line, usually diagonal, running out of the top corner of a window or a door. That is the framing behind the plaster moving, and the crack is the wall relieving it. Filling that with a rigid patching compound is wasted work, because the joint will keep moving and the patch will crack straight through in the same line. It needs a sealant that can stretch.

The third group is the one where we stop. A crack wide enough to take a coin, a stair step pattern following the line of the lath, or a crack with a lip where one side sits proud of the other, means something has moved that is not the plaster. That belongs to a structural engineer, not to a painter. We will point it out and we will not quote a coating over it.

Repairing What Can Be Repaired

Hairline and map cracking gets filled with a flexible patching compound worked into the crack rather than smeared across it, then textured to match the surrounding finish while it is still workable. Matching a float finish, a dash coat or a heavy lace pattern is most of the skill, and it is why a repair done badly reads as a pale stripe across the wall the first time the sun comes in low. We keep a small board of the common local textures to work against.

Stress cracks are treated differently. The crack gets cut open slightly with a grinder or a crack chaser to give a proper cross section, cleaned out, backed where it is deep, and filled with an elastomeric sealant that can stretch with the joint underneath. Then it is textured over. That joint is still going to move, so the aim is not to lock it, it is to give the movement somewhere to go without splitting the surface.

Bare plaster left exposed by any of this gets a masonry primer before topcoat. Fresh patching material and old weathered stucco absorb very differently, and skipping that step is how a repaired area ends up a slightly different sheen from the rest of the wall, visible from the street on a bright day.

When Elastomeric Is the Right Answer

An elastomeric coating is a high build, flexible, waterproof film. Dry, it is many times the thickness of ordinary house paint, and it stays elastic enough to bridge a hairline crack and keep bridging it as the wall expands and contracts. On a badly map cracked wall in sound condition it is a very good product and it will hold for a long time.

It has one serious condition attached. It seals the outside face of the wall, so whatever moisture gets into that wall has to leave some other way. In Long Beach, where the marine layer sits on a house most mornings and salt air comes off the harbour and the breakwater, that condition is not academic. If a window flashing has failed, a hose bib drips, sprinklers throw at the wall, or soil has been banked up over the weep screed, the water goes in and cannot get back out. It collects behind the film, and then the film comes off in sheets.

So before we quote a coating we check where water could be entering, and we check whether the wall is dry now. If we find a source, that gets fixed first or the coating does not go on. If the house has a reason it cannot be sealed, we will tell you and quote a breathable acrylic instead, which costs less and is the better job on that particular wall.

Applying It Properly

The number that matters on an elastomeric system is dry film thickness, and the product data sheet gives it. Hitting it is a matter of spreading rate and coats, not of how the wall looks when it is wet. Spread too thin to save material and you have an expensive paint job with none of the crack bridging you paid for, which is the most common way this product disappoints people. In practice it means two coats and a great deal more material per square foot than a repaint.

Surface has to be clean and dry, so the wall gets washed and given time. We do not start spraying while the morning damp is still on it. Recoat windows and cure times matter too, because a coating that has dried on the surface has not necessarily cured through, and loading a second coat on too early traps solvent and softens the film.

Call (562) 950-8749 and we will come and read the wall before anybody talks about product.