Homeowner’s Guide to Pressure Washing a House

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.

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.

Select your pressure washer

You need a washer that produces at least 2,000 psi (pounds per square inch) of pressure. Both gas and electric models can produce that much pressure, so it’s your choice. If you rent one, it’ll cost about $70 to $100 per day, and you’ll need it for a full day. You don’t have to be experienced to use one, but be prepared for a day of physical labor.

If you rent a gas-powered model, it’ll probably 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 oversize squirt guns, but they aren’t toys. Don’t point the nozzle at anyone or try to rinse your hands or feet; they can tear skin right off. If you don’t feel confident operating it, hire a pro.

Finally, make sure you get a six- to 12-ft. extension wand to help reach high areas.

Hook up the pressure washer

Connect the pressure washer to an outdoor faucet using an ordinary garden hose. Attach a nozzle (see “Select 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.

Select the Best Nozzle

Pressure washers usually come three or four nozzles with spray patterns of varying widths. Attach the 15-degree (yellow) or 25-degree (green) nozzle to the wand for general paint cleaning, then test the effect on the siding. 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 you need more cleaning power, try a nozzle with a narrower pattern or a turbo nozzle, but don’t (repeat, don’t) use the red, zero-degree nozzle. It’s powerful and can quickly damage wood, stucco and other materials.

Also, make sure the nozzle coupling locks into place securely so you don’t blow it through a neighbor’s window when you fire up the machine!

Nozzle patterns

Practice first

Practice handling the pressure 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 two feet 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.

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.

Scrape after washing

A pressure washer will remove loose paint, but it’s not a substitute for scraping. We’ll have to scrape additional loose paint after pressure washing this area anyway.

Do I have to remove all of the old paint before painting a house?

No. It’s safe to paint over existing paint that’s still sticking well to the siding and is generally in good condition. You do, however, have to remove paint that is flaking, peeling, cracking, bubbling or showing defects that will show up under the new paint and/or prevent it from adhering.

Don’t hold the nozzle too close

If you hold the nozzle too close (typically closer than six inches) 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.

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 them underneath.

Use an extension wand

Use an adjustable extension wand (six- 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!

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 (or TSP substitute) mixed in water. Begin from the lower areas and work upward, rinsing frequently. Keep the siding below you damp so the TSP won’t leave visible drip marks. When finished, rinse from the top down using a garden hose.

• Pro tip: An add-on ladder stabilizer makes the ladder more secure.

Should I ever bring my pressure washer up on a roof?

If your roof isn’t too steep (the pitch is less than 6/12), your pressure washer is light enough to carry up a ladder and the hose and/or power cord are long enough, you can use the pressure washer to wash dormers, chimneys and the like, but use discretion. Don’t try to use a pressure washer on a roof that you already feel queasy about walking on, and don’t use a pressure washer if there are power lines close to the roof (less than six feet away).

Pressure washing tips

• If you haven’t handled a pressure washer before, be sure to take a few minutes to practice, get a feel for the wand, and choose the most effective spray pattern. For better control and to keep your arms from tiring, use two hands.
• While it’s best to wash with the wand aimed downward, at times you’ll have to point it somewhat upward, especially under soffits. 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.
• Stripping loose paint and gouging the wood in the process 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.

Warning: Steer clear of electrical devices like lights and outlets. You can easily cause a ground fault or break them. Keep the wand and water stream at least six feet away from electrical wires. A shock from your service wires can kill you.