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How to Pressure Wash a House

Paint prep simplified

How to pressure wash a house to prep for paintFamily Handyman

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.

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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. Using a pressure washer to remove paint is 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?

Photo 1: Check for chalking

Rub your hand over the painted surface and look for a powdery light-colored residue, the sure sign of chalking. Pressure-washing will scour it off to ensure a good bonding surface for the new coat.

Photo 2: Repair before washing

Replace rotten boards and renail loose ones before pressure washing, so you don’t drive water through the siding and into the wall.

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

Photo 3: Hook up the pressure washer

Connect the pressure washer to the outdoor faucet through an ordinary garden hose, attach a nozzle (see “Selecting the Best Nozzle,” below) and start the engine. Wear goggles to keep paint chips and dirt out of your eyes, and clothing that can get soaked. You WILL get wet. Spread old sheets or painter’s cloths on the ground and over shrubbery to catch paint chips.

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).

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

Photo 4: Practice first

Practice handling the washer in a low area first. Hold the wand with two hands and move it across the siding from side to side at a steady pace. Start about 2 ft. from the siding, then move closer until you find the optimal cleaning distance. In general, work at a horizontal or slightly downward angle to avoid driving water up under the siding.

Photo 5: Work from the top down

Begin washing the walls at the top and work down. Wash the gutters and soffits as well as the siding. Direct the spray away from breakable objects like windows and outside lights, and remove house numbers and window boxes whenever possible.

Photo 6: Scrape after washing

Pressure washers will remove loose paint, but they’re not a substitute for scraping. We’ll have to scrape additional loose paint after pressure washing this area anyway.

Photo 7: Oops!

If you hold the nozzle too close or for too long in one spot, you’ll gouge the wood. We’ll have to fill this area with wood putty before repainting. Gouging is inevitable if you try to strip paint.

Photo 8: Point away from windows

Direct the nozzle away from windows, holding the wand at an angle so you don’t drive water into joints, gaps or against the glass. Even so, check the sill on the inside and dry up any water that leaked through. Remove the shutters after washing and wash underneath.

Photo 9: Use an extension wand

Use an adjustable extension wand (6 to 12 ft.) to wash high areas. At full length, the wand takes some muscle to handle. Good control takes some practice, but it’s safer than pressure washing from a ladder. Remember to close all the windows!

Photo 10: Scrub inaccessible areas

Clean high areas beyond the reach of the pressure washer extension with a scrub brush and a solution of detergent and TSP mixed in water. Begin from the lower areas and work upward, rinsing frequently. Keep the siding below damp so the TSP won’t leave visible drip marks. When finished, rinse from the top down using a garden hose. An add-on ladder stabilizer makes the ladder more secure.

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 pressure washing 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.

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.