Basement & Porch Floor Painting in Wilmington, DE

Concrete is porous. Water vapor from the soil beneath a basement slab rises through it and out of the top surface, and a coat of paint traps that vapor just under the film. Pressure builds, the paint blisters and then flakes away in patches. A white, powdery crust on bare concrete, called efflorescence, is salt left behind by water that has passed through, and paint does not bond to it. A smooth, hard-troweled slab gives paint little to grip, so the surface has to be cleaned and opened up before the first coat.

A wooden porch floor fails where water stays. Paint lets go first at the seams between boards, at the cut ends along the front edge, and anywhere the porch has settled into a low spot that holds a puddle. Underneath, the cut end grain soaks up water. Each board is checked for rot, and paint over a rotted one only hides the problem for a season. Soft wood is found and repaired first, as carpentry ahead of the paint.

Repainting starts with the paint already there. Sound, well-bonded paint can be cleaned, roughened, and painted over. Peeling paint has already lost its grip, and new paint applied over it comes off with it, so the loose paint comes off first. The cause of the peeling matters as well: if it was moisture in the slab or water in the boards, a new coat will fail the same way unless that is addressed. A floor that would be better covered with tile or new boards is flooring work.

A slab can look dry and still be passing water vapor. One plain check is a square of clear plastic, about 2 feet on a side, taped tight to the bare floor at every edge and left in place for a day or so. Droplets under the plastic or concrete that has darkened beneath it indicate moisture rising through the slab. A slab that shows it is a poor candidate for paint until the source is understood.

The same look takes in cracks. Hairline shrinkage cracks are normal in concrete and can be filled before painting. A crack with one side higher than the other, or one that lets water in, is a sign of movement or a leak, and filling it does not fix either.

A concrete stoop on a Wilmington row home takes foot traffic straight off the sidewalk, and in winter it takes rock salt as well. Salt and meltwater sit on the treads and work under paint at the front edge of each step first. So a stoop is washed clear of salt residue and left to dry before prep starts, and the worn nosings get the closest look, since that is where a new coat would let go first.

Wooden porch floors are laid as narrow tongue-and-groove boards, pitched toward the yard so rain runs off. Where a porch has settled, and the pitch has gone flat or turned back toward the house, water sits on the boards and in the grooves, and that is where the paint and then the wood go first.