Glossary
House Washing Glossary
25 terms people ask about, each in a sentence or two. Every definition links to its source and to a full guide. For numbers, see the statistics page.
A
- Artillery fungus
A mulch fungus, Sphaerobolus stellatus, that shoots sticky spore masses about 1 to 2 mm across onto siding, cars and other light-colored surfaces, more than 6 feet up and over 20 feet out. It is not considered a pathogen of plants, animals or people, but dried spots must be scrubbed and scraped off, and power washing has given mixed results.
C
- Chalking (siding oxidation)
A dull, powdery film that is common on pigmented materials exposed to sun and weather, such as vinyl siding and paint. Light chalking is a normal way for paint to weather; heavy chalking means the coating is eroding.
D
- Deck brightener
An acid wood treatment, usually oxalic or phosphoric acid, used after cleaning or stripping a deck. It neutralizes the stripper, is used on rust stains and to speed tannin fading, and restores the natural look of cedar or redwood before staining.
E
- Efflorescence
A white, chalk-like deposit on concrete tile. Free lime in the cement reacts with water and carbon dioxide to form it. It is superficial and usually goes away on its own.
- EIFS (synthetic stucco)
Exterior insulation and finish system: insulation board attached to the wall, a reinforced base coat and a textured finish coat. It usually feels hollow and flexes when pressed, and one maker caps cleaning pressure on it at 500 psi.
F
- Fiber cement siding
Siding made from cement and fibers. One maker's care guide says to keep pressure below 1,500 psi, stay 6 feet from the wall with a wide fan tip, and avoid acid, because high-pressure washing can damage the surface.
G
- GPM (gallons per minute)
A pressure washer's water flow rating. One manual says the greater the GPM, the greater the flow or rinsing power produced.
- Gutter brightening
Removing oxidation from gutters with a dedicated oxidation remover. One product label gives a 10:1 dilution for gutter brightening and says to prewet the area, test an inconspicuous spot and not let it dry on the surface.
H
- Hot-water pressure washer
A pressure washer that pushes water through a heated coil, bringing it to about 200°F before the wand. One 4 GPM unit's burner uses 2.21 gallons of fuel an hour.
M
- Mildew (on siding)
Growth on the dirt film that collects on siding, worst in warm climates with high humidity and in spots rain doesn't reach, such as under eaves and porch enclosures.
- MS4 (storm drain system)
A municipal separate storm sewer system: a city's storm drain system. The EPA says it is not part of a sewage treatment plant, and its stormwater is often discharged untreated into local water bodies.
N
- NPDES permit
The Clean Water Act permit required to discharge pollutants through a point source into U.S. waters. Without one, nobody may discharge pollutants that way.
O
- Oxalic acid
The acid in many commercial wood cleaners. A 5% solution neutralizes blue-black iron stains in wood.
P
- Polymeric sand
Paver joint sand mixed with special additives that harden it in place. It needs at least 48 hours without rain to set, and it is not used on permeable pavers because it blocks water from draining through.
- Pre-wetting plants
Spraying surrounding plants with water before a bleach-based cleaner goes on, and again after use. One soft-washing guide says the salt left behind when the cleaner dries is what burns plants.
- PSI (pounds per square inch)
The water pressure at the nozzle tip. Brick industry guidance calls under 100 psi very low pressure, 100 to 400 psi low pressure, and over 800 psi high pressure, which it says is not appropriate for cleaning brick.
R
- Roof algae streaks
Brown to black discoloration on asphalt shingles that can be mistaken for soot, dirt, moss or tree droppings. A shingle maker says studies show the algae growth is not harmful to the building envelope.
S
- Sodium hypochlorite
The active ingredient in household bleach; a 5% solution is ordinary household bleach. One house-wash cleaner lists it at 3 to 7% on its safety data sheet, which warns not to mix it with acids, ammonia or other household chemicals because dangerous fumes may result.
- Soft washing
Cleaning siding or painted surfaces with low pressure plus a cleaning solution instead of high-pressure water. One washing company calls it the right tool for stucco, which it says high-pressure washing damages.
- Sugaring (weathered stone)
When the grains of weathered marble or limestone loosen and come off on your fingertips. A park-service brief says that if a marker is fragile, even low-pressure water can be damaging.
- Surface cleaner
A pressure-washer attachment in which a spray bar with a nozzle at each end spins under water pressure, keeping the nozzles at a fixed height to avoid the streaks and uneven cleaning of a hand-held nozzle.
T
- Tannin stains
Stains that come from tannins in leaves. On concrete pavers, leaf tannins bond to the surface and are hard to remove; on composite decking, one maker says to allow at least 12 weeks of normal weathering for tannin leaching to fade.
- Tiger stripes (gutters)
Streaks on gutters, left where rainwater runs over asphalt shingles, picks up petroleum-based particles, leaf tannins and pollution, and drips over the gutter edge. One seller of stripe removers says soap and water, all-purpose cleaners and even pressure washing from below fail on them.
V
- Vinyl siding (washing limits)
Vinyl siding can be power washed with caution, but the siding trade group says not to aim the stream upward, which forces water behind the panels, and some siding makers do not recommend power washing at all or set pressure limits.
W
- Wet-look sealer
A paver sealer that deepens the color of the stone and may add gloss. Paver sealers also help resist fading from strong sun and need reapplying every 3 to 5 years.