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How to Pressure Wash a House

A pressure washer cleans old paint fast. Here's how to pressure wash your whole house so that the new coat of exterior paint will stick better and last longer.

By the DIY experts of The Family Handyman Magazine

Save time on paint prep

A pressure washer is one of the best time-saving tools to come along in years. Its high-velocity water spray cleans dirt, grime and chalking paint from otherwise sound painted surfaces. Pros like pressure washers not only because they're fast, but because they scour the old paint so the new coat will adhere better. It definitely beats the old garden hose, scrub brush and TSP cleaning method, a task so slow that many people just skip it.

In this story, we'll show you how to pressure wash your home effectively and safely, from start to finish, without ruining the siding or compromising the future paint job. If you're lucky and your paint is sound (no peeling), pressure washing may be the only prep work needed.

Should you pressure wash?

A pressure washer excels at scouring away dirt, grime and especially chalking, the powdery pigment left on the surface when old oil and some latex paints deteriorate. The scouring action is so strong that you won't need a cleanser (TSP or non-phosphate substitute) like you would if you washed the surface by hand.

First off, look for dirt, especially up under the soffits. And then rub the paint surface to check for chalking (Photo 1). If the previous coating was 100-percent acrylic latex paint, it probably won't chalk. If the painted surface is clean and not chalking, pressure washing is optional. But most pros do it anyway to make sure the new paint will adhere well.

The high-pressure stream of water will blast away loose paint too, but resist the temptation to use it as a paint removal tool. The high pressure can easily gouge wood siding or knock the mortar from between bricks. Besides, the pressure washer can't do a complete scraping job. You'll have to scrape off additional paint anyway, so you won't save much time.

Pressure washing works on wood, vinyl, aluminum siding and masonry, but due to its high pressure, we don't recommend it for hardboard siding. Hardboard is more vulnerable to moisture than wood and it's extremely difficult to repair if you accidentally gouge it.

Pressure washing won't stop mildew. (It'll wash most of it away, but the mildew will soon grow back.) Mildew resembles a dirty-looking blackened area. To identify it, apply a little bleach. If the black spots disappear, you have mildew. Using a scrub brush instead of the pressure washer, wash the area with a mixture of 1 part bleach to 9 parts water. If the bleach test had no effect on the black spots, they're dirt and you can pressure wash them away.

Warning: Pressure washing is not a safe paint prep method if the exterior paint contains lead. If your home was built before 1978 (when lead paint for residential housing was banned) or if you're unsure, have your paint tested or contact your local health department for safe handling instructions.

Time and money

Rent a washer that produces at least 2,000 psi (pounds per square inch) of pressure. It'll cost about $70 to $100 per day, and expect to keep it for a full day. You don't have to be experienced to use one, but be prepared for a day of physical labor. The washer will probably be gas-powered and weigh more than 75 lbs. Depending on its size, you might need a pickup or van to haul it and help to unload it. Ask the rental agent to show you how to hook it up and operate it, and to review safety precautions with you.

Pressure washers look like the ultimate squirt gun, but they aren't toys. Don't point them at anyone or try to rinse your hands or feet. They can tear your skin right off. If you don't feel confident operating it, hire a pro.

Finally, make sure you get a 6- to 12-ft. extension wand to help reach high areas (Photo 9).

<p>Pressure washer nozzles</p>

Pressure washer nozzles

<p>Lock the nozzle</p>

Lock the nozzle

Selecting the Best Nozzle

Pressure washers usually have three or four nozzles with spray patterns of varying widths. Attach the 15- or 25- degree nozzle to the wand for general paint cleaning, then test the effect on the siding (Photo 6). The spray should clean away all dirt and chalk without damaging the siding. Rub the surface with a clean glove to make sure the chalk comes off. If it doesn't, try a nozzle with a narrower pattern. Don't use the narrow, zero-degree nozzle. It's powerful and can quickly damage wood, stucco and other materials (Photo 7). Also make sure the nozzle coupling locks into place securely so you don't blow the nozzle through a neighbor's window!

Pressure washing techniques

Follow the photo series for the pressure- washing basics. If you haven't handled the tool before, be sure to take a few minutes to practice, get a feel for the wand, and choose the most effective spray pattern (Photo 4). For better control and to keep your arms from tiring, use two hands.

Other tips:

  • While it's best to wash with the wand aimed downward, at times you'll have to point it somewhat upward, especially under soffits (Photos 5 and 9). When you do, remember the general rule not to drive the water directly into cracks or gaps. And always avoid shooting water up into soffit vents.
  • We don't recommend that you pressure-wash while standing on a ladder; the recoil from the pressure can knock you off balance.
  • Steer clear of electrical devices like lights and outlets (Photo 5). You can easily cause a short circuit or break them.

Warning: Keep the wand and water stream at least 6 ft. away from electrical wires (Photo 9). A shock from your service wires can kill you.

  • Stripping loose paint (Photo 6) and gouging the wood in the process (Photo 7) is the most common rookie mistake and will leave you with time-consuming, difficult wood repairs.
  • Give your house at least a week of good drying weather before applying paint.

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Required Tools for this Project

Have the necessary tools for this DIY project lined up before you start—you’ll save time and frustration.

    • Bucket
    • Extension cord
    • Paint scraper
    • Rags
    • Safety glasses

You'll also need a garden hose and a pressure washer.

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