Pressure washing the exterior of your home can be a controversial choice. While it can be an effective tool on surfaces like driveways and sidewalks, it can do more harm than good to a home’s exterior. Houses can withstand a variety of weather conditions, but they were not designed to have high-pressurized water blasting at them.
Even moderate pressure can leave lasting damage: gouges in wood, furring of the grain, cracking, chipping and splintering. Brick or mortar, vinyl siding and window seals are also vulnerable to water intrusion or loosening caused by high-pressure cleaning.
If you’re considering pressure washing purely for cleaning (rather than preparing for repainting), you must proceed with caution. Removing old paint or creating an uneven sheen can leave your house looking worse — and that compromised finish will persist until your next paint job.
Even more concerning is the damage that may not be immediately apparent. Water can get up into your soffits or seep behind your siding. Anywhere a house has gaps is a potential entry point for high-pressure water to work its way in, Once it’s in the wall cavity it can be difficult for it to evaporate, creating conditions for rot and mould.
In this case, the house exterior is stained cedar shingles — a very soft wood which could be easily damaged from a pressure washer set too high or sprayed too close.
How to Clean Fibre Cement & James Hardie Siding Safely
Materials such as James Hardie Board or fibre cement siding are similarly at risk of marring and damage. The James Hardie manufacturer cautions against high pressure cleaning. The method they recommend for cleaning James Hardie siding is to use a low pressure spray combined with a soft non metal bristle brush or rag and mild non-abrasive detergent for stubborn stains. Damage from incorrect cleaning may even void your warranty.
Never Pressure Wash A House That Has Lead Paint
It’s never a good idea to pressure wash a house that has lead paint, even if it’s buried deep in past layers. You don’t want to run the risk of dislodging lead paint chips or spread lead dust across your soil and landscaping – putting your family and pets and future occupants for years to come at risk.
Safe DIY Way To Clean A House Exterior
If you want to do routine cleaning without risk of damaging your house, opt for a gentle approach: an extension pole fitted with a medium stiffness brush, and a garden hose with a spray nozzle. Skip abrasive brushes or scouring pads.
You’ll get the job done safely by using water and light agitation rather than high pressure. A diluted mild soap or all purpose cleaner will handle most dirt and grime. For mould or mildew, use a specialised cleaner as directed – always protect nearby plants, pets and landscaping. If you can’t reach high areas this way then consider a cleaning company, as mentioned in the sections below.
When to Hire a Professional House Cleaning Company
If exterior cleaning feels daunting, look for local house cleaning companies that use a soft-wash system, a lower pressure application water and cleaning solutions designed to preserve siding, windows, and other surfaces. Reputable companies will ensure water does not enter your home’s building envelope and understand the risks of pressure washing.
Why Pressure Washing Alone Won’t Eliminate Mold, Mildew or Algae
High-pressure washing may remove surface growth, but it doesn’t kill spores. In fact, it can spread them across your home’s exterior where they regenerate. Furthermore, where there is accumulated mold or mildew, there is a tendency to increase the pressure or get closer to the surface, increasing chance of inflicting damage to the house exterior. For effective removal, an appropriate cleaner must be applied, lightly agitated, then rinsed.
What Surfaces Are Appropriate For Pressure Washing?
Pressure washing can be an effective cleaning tool when used at appropriate pressures to clean decking and at medium to high pressure for patios, pavers, sidewalks, and driveways. When cleaning these kinds of surfaces, caution must still be exercised. Decking can be harmed with too much pressure and concrete and asphalt can suffer from pitting and surface degradation, as well as having pieces blasted away, particularly at the edges and seams.
Be especially cautious when washing near your home’s siding — debris or rock fragments propelled by high pressure can chip paint and crack glass.
Should I Pressure Wash A House To Prepare It For Painting?
You can, but you need to understand the risks. Pressure washing is often used to prep for painting, but it comes with risk. Blasting away old paint may achieve bare surfaces, but often causes damage to the substrate and there’s the risk of water getting behind your siding. If the house exterior is caulked and painted shortly thereafter you risk further trapping the moisture in. The alternate methods above are safer options that are not going to comprise your house.
In Summary
If any type of surface on your property is being pressure washed make sure the individual doing it is experienced and knows how to handle the machine. The pressure washer is only as safe and effective as the person controlling it. Unskilled use can cause costly, long-term damage.
Keeping up with the maintenance and painting of your house will ensure your home stays in top condition. Learn more in our guide: How Often To Paint Your House Exterior
We’re a local Nanaimo painting company with over 20 years of experience. As a husband-and-wife team, we take pride in providing personal service and exceptional craftsmanship.
Contact Parnell Painting today by email or phone to schedule a free, no-obligation estimate. We’ll help you bring fresh colour and lasting beauty to your home.
