Everybody pressure washes their house. But few people know that the way it’s usually done is NOT good for your house.
You may just be going with the crowd, but in this case the crowd is wrong, and you’re likely causing big damage you have no idea about.
Pressure washing is usually the first step in getting a new paint job so I see a lot of painters doing it and doing it wrong.
It’s not just unknowing homeowners doing this, it’s the professionals as well! Painters and pressure washing companies walk away from a house with a clean exterior, but the work they did has caused untold damage inside the walls of the house and other places.
There are four main reasons you should never pressure wash your house. Four ways that pressure washing does more harm than good. At the end, I’ll discuss the right way to way wash the outside of your house, but first the bad way.
Reasons to NOT Pressure Wash
#1 Water in the Walls
To me this is the worst kind of damage you can do with a high pressure washer to a house. Commercial pressure washers shoot water at pressures starting at 1500 psi which isn’t too destructive but they can go upwards of 3300 psi which will blast through solid wood, asphalt and even concrete (I’ve done it) if they’re close enough.
If you have a wood frame house with any kind of wood siding (clapboards, shiplap, board and batten, shingles, etc.) there is an excellent chance that washing your house with a high pressure washer will shoot water up under the siding, potentially soaking wall cavities, insulation, wiring, flooring, plaster, etc. Nothing is beyond the reach of these powerful water guns.
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Once the water is in the wall it is often difficult for it to evaporate. Often in the painting process a house is pressure washed, then caulked and patched and finally painted. Essentially the painter is soaking the inside of the walls and then sealing the water in with a fresh coat of caulk and paint.
I have seen moldy insulation, crumbling plaster, and cupped flooring all from a pressure washer’s work. Nothing in your walls likes to be wet so keep it dry.
#2 Missing Mortar
A lot of people think that since they have a brick house they are safe to pressure wash. Think again! Old brick and mortar are softer than the new stuff today and can be easily blasted away with high pressure water.
I’ve seen brick houses with the mortar almost completely blasted away by pressure washing. And the expense of repointing a brick house is probably 10 times what the pressure washer charged you to wash your house.
#3 Gouged Wood
When pressure washing a lot of painters will get right up close to the surface to try to blast loose paint off. They often succeed and then that 3000 psi water is blasting right into bare wood. It digs holes in the surface and furs the wood grain up damaging the siding.
Unless you’re into carving your name into the side of your house with water this is yet another reason not to pressure wash.
#4 Lead Paint
It’s always there lurking beneath the surface on an old house. We all want it gone, but removing paint with high pressure water is not the solution.
It causes lead paint chips both small and large to be blasted all around the yard and get mixed into the soil where the kids can potential ingest it.
If you don’t have kids think about the neighbors or the next folks. Lead paint is everyone’s responsibility. Read more about lead paint safety here.
When You Should Pressure Wash
Don’t think that I am against pressure washers. They are a great tool, I just see them being misused way too often. There are times and projects where a pressure washer is the best tool for the job and I want to be sure to mention those as well.
Some projects work best with high pressure (2000-3000 psi) and others with lower pressure (1250-2000 psi)
- Decks (Low pressure)
- Railings (Low pressure)
- Wood Fences (Medium pressure)
- Vinyl Fences (Medium pressure
- Asphalt (Medium pressure)
- Concrete Driveways & Sidewalks (High pressure)
- Metal Patio Furniture (High pressure)
- Stone and Pavers (High pressure)
So if pressure washing is dangerous for your house what can you do to get things clean?
The Low Pressure Option
I’ve found that using a homeowner grade pressure washer allows me to safely wash a house with the pressure low enough to be relatively safe and I’ve outlined my methods in an earlier post Pressure Washing an Old House.
Ultimately the safest way to clean and prep the exterior of your old home (especially wood houses) is to use a regular garden hose and spray nozzle along with an extension pole with a nylon scrub brush.
It takes longer, yes, but it actually does a better job at cleaning the house and preparing for paint in addition to being a hundred times safer for your house.
I’m not sure how many of you will follow this advice, but I would be remiss to not tell you the dangers. What you decide to do with the information is up to you!