Pressure washing costs in New Orleans

The exterior maintenance checklist that the Historic District Landmarks Commission wrote for older New Orleans houses has a line for asbestos shingle siding, right beside wood siding. For cracked, worn or missing shingles, it says to replace them with non-asbestos shingles that match. It also says great care should be taken with broken asbestos products.

For mold, algae or mildew on wood siding and trim, the same checklist says to clean and treat the surface to hold back new growth. It says not to use high-pressure water, since that could cause more significant problems. And the guide's property checklist suggests trimming tree limbs to 5 feet from the house, because their shade can lead to moss, mold and algae.

Brick piers, chain walls and masonry houses get firmer rules in the HDLC's districts. Its masonry guidelines don't permit cleaning with power washing, harsh chemicals, metal brushes or grinders. They call for water pressure generally no more than 100 psi, and repointing open mortar joints before any water cleaning.

Even the water is on its list. The commission wants it clean, without excess salts, acids or minerals, and without traces of iron or copper that can stain masonry.