By Jennifer Noonan, Bob Vila
Using Too Much Pressure
If you use too much pressure while power-washing, you could punch a hole in vinyl siding, etch concrete, or splinter wood. Avoid damage by adjusting the pressure on the power washer and making sure you stand sufficiently far from the surface you're washing.
Using Only Water
Almost all power-washing jobs require the help of a detergent or chemical cleanser. Begin your power-washing project by spraying the area with an appropriate, environmentally safe detergent that can break up dirt and kill mold. Apply according to the product's instructions, letting it sit if necessary, then power-wash it off.
Not Protecting Landscaping
Before you start power-washing, thoroughly wet down adjacent plantings with a garden hose. This will help ensure that the cleanser you use won't dry on foliage and leave burn marks. If your project takes longer and the plants start to dry off, you may need to water them again. Depending on the chemicals you're using, however, you may instead want to protect the plantings with a tarp.
Power-Washing Painted Surfaces
Some painted surfaces may not stand up to even a gentle power-washing, especially if they are old or have been exposed to sunlight for long periods. Avoid using a power washer on anything that is painted.
Power-Washing Mold-Prone Surfaces
Surfaces like drywall or fabric may not be able to thoroughly dry out before developing mold, and as a result should not be power-washed.
Washing in the Wrong Sequence
If you are washing an entire house, start with the roof—although, depending on the roofing material, power-washing may be a bad idea. (Particularly with asphalt shingles, avoid high-pressure jets of water.) After you've cleaned the roof, work your way down the exterior, then tackle the porch or patio, and finish up with the windows. If you start with the exterior or porch first, the runoff from cleaning the roof will make them filthy again.
Using Hot Water
Commercial power-washing contractors use hot water in industrial applications because it cleans faster. Residential exteriors are not as sturdy as commercial exteriors, and you could actually warp your vinyl siding or damage other elements like cedar shakes or shingles if you use hot water while power-washing.
Not Knowing Your Equipment
If you don’t know how to use the equipment properly, you can do serious damage while power-washing. Make sure you get a thorough demonstration of any rental equipment before leaving with it. And if you have purchased a power washer, read through the instruction manual before using it.
