How to Clean a Brick House

The brick is fine, the mortar is the weak point

Fired brick is hard and handles cleaning well. The mortar joints holding it together are softer, and on an older house considerably softer. High pressure erodes mortar out of the joints, and once it is gone water gets into the wall and the repair is repointing, which is a real expense. On a house built before the mid twentieth century the mortar is often lime-based and much softer again, so the margin is smaller than people expect.

The practical rule is to work at the lowest pressure that does the job, keep the spray moving, and never hold a jet on a joint.

Know what you are removing

Green and black growth is organic and comes off with a cleaning solution. White powdery bloom is efflorescence, mineral salt from within the brick, and it is not dirt. Dark grey film on a street-facing wall is usually traffic and exhaust residue. Orange staining is rust from a fixing or from irrigation water. Each wants different treatment, and using one product for all of them gives a patchy result.

Efflorescence

This is the one most people misdiagnose. Efflorescence appears as a white haze that seems to come back no matter how often the wall is washed, because water moving through the masonry keeps carrying salt to the surface. Washing dampens the wall, which brings more up. Light deposits brush off dry. Persistent efflorescence is a moisture problem, and the fix is finding what is wetting the wall: a leaking gutter, ground level built up against the brick, a failed damp course, or splashback from a hard surface below.

Painted brick

Painted brick is a different job entirely. Pressure lifts failing paint in sheets and leaves an edge that has to be dealt with, and on pre-1978 housing disturbing old paint raises lead-safety questions that are worth taking seriously. If the paint is sound, wash it gently as you would painted siding. If it is failing, cleaning becomes surface preparation and should be handled as such.

Method

Wet the wall first so the brick does not absorb cleaning solution straight into its pores. Apply the solution low to high, give it dwell time without letting it dry on the surface, then rinse top to bottom at moderate pressure with the spray angled so it is not driving into the joints. Keep the whole elevation damp as you work to avoid tide lines.

Having it done

We match pressure to the age of the mortar rather than the hardness of the brick, and we identify what the staining actually is before choosing a product. Call (504) 688-3995 for a free written estimate.