Primer and Sealing

Primers Are Not Interchangeable

There is a persistent idea that primer is a cheaper white paint you put on first. It is not. A primer is a problem-solving coat, and there are several distinct kinds because there are several distinct problems. Using the wrong one is worse than using none, because it puts a layer between the surface and the finish that neither one is bonded to.

On a house that has failed, the primer decision is the decision. Get it right and an ordinary finish coat will hold for years. Get it wrong and the best paint on the shelf comes off with the powder underneath it.

Bonding Primer, for Chalked and Glossy Surfaces

A chalked wall is covered in loose pigment. Nothing sticks to loose pigment. Washing removes most of it, but on a badly weathered south or west elevation there is always some left in the texture that a wash will not reach, and that residue is what a bonding primer is for. A penetrating bonding primer is thin enough to soak into what remains and bind it back into a solid film, so the finish coat is attached to the wall rather than to dust.

The same product solves the opposite problem, which is a surface too slick to grip. Old alkyd enamel on trim, previously glossed doors, and hard mineral surfaces all fail the tape test with an ordinary primer. A bonding primer bites into them where a standard acrylic just lies there.

We test rather than assume. If a dark cloth comes back loaded with pigment, that elevation is getting a bonding primer whether or not the rest of the house needs one.

Stain-Blocking Primer, for Bleed and Marks

Some things come through paint no matter how many coats go on. Tannin in old redwood and cedar siding is the common one here: it dissolves in the water of a latex coating and rises through it as a brown or pink stain, often only after the second coat has dried and everybody has gone home. Water damage from a past leak, smoke, rust bleed from old fixings and marker all behave the same way.

The fix is a coat that the stain cannot travel through, and the correct choice depends on the stain. Some need a shellac-based blocker, some are handled by a good oil or a modern water-based stain-blocking primer. What none of them are handled by is an extra coat of finish paint, which is the usual attempt and which costs a full coat of material to fail.

Masonry and Stucco Primer

Bare stucco is alkaline and porous, and both properties matter. A masonry primer is formulated to tolerate the alkalinity and to even out the suction so the finish coat does not flash dull in some places and glossy in others. Fresh patchwork is even hungrier than the surrounding wall and needs sealing or the repair reads as a shadow through the topcoat forever.

This is where elastomeric coatings usually come up, and where the honest answer is a qualified one. Elastomeric films bridge hairline map cracking in stucco, which is genuinely useful on the post-war tract housing east of here. But they are thick and they are close to vapor-closed, and on a wall that is getting water from behind, or on a coastal wall that needs to dry outward after a damp morning, that film traps moisture in the assembly. Then it blisters in sheets, which is a far worse failure than the cracks you started with. We use elastomeric where the cracks are non-structural and the wall can dry. Otherwise we do not.

Spot Priming and Full Priming

Not every house needs to be primed wall to wall. On a sound, lightly chalked surface, spot priming the bare and repaired areas and going straight to finish elsewhere is the right call and saves you a coat of material.

A full prime is warranted when the surface is uniformly chalked, when there is a large color change from dark to light, when previous coatings are mixed types across the same elevation, or when the substrate has been exposed by scraping over a wide area. We will tell you which of those applies to your house and why, and it will be on the quote as its own line rather than buried.

What We Will Not Do

We will not put an ordinary primer over heavy chalk to save a step, we will not seal a wet wall, and we will not use a stain blocker as a substitute for finding out where the water came from. Each of those is a way to make the house look finished for one season and fail in the second.

Call (562) 586-5087 and we will tell you which primer your surface actually needs.