The quick answer is yes, pressure washing can degrade a concrete surface. Visible damage can be seen due to water pressure at the level at which even lightweight pressure washers can operate. So, if you're not careful, it can cause irreversible damage to your driveway or patio. Yes, a pressure washer can damage concrete.
Of course, this depends on the hardness of the concrete, whether it is damaged, how often it is damaged, the pressure of the water and the nozzle you use. Be sure to use the correct nozzle and do not adjust the water pressure above what is necessary. Do not attempt to remove sealants or coatings with a pressure washer. Often, this leads to an excessive concentration of water pressure in small areas, which eliminates the upper part of the concrete and leaves engraving marks.
Most of the strength of concrete is found in the top layer. Once this layer has been removed, concrete is highly susceptible to decay and damage. Pressure washing is an effective cleaning regime for concrete, provided that the concrete is in good condition and is more than a year old. However, if performed incorrectly, pressure washing could permanently damage the concrete surface, which could require extensive repairs.
In addition, after pressure washing, it is good practice to seal the concrete surface to protect it from future stains and dirt. If you notice that your pressure wash leaves marks on the concrete surface, don't panic. There are a lot of horror stories about pressure washing that focus on a well-meaning homeowner who accidentally damages his wooden deck, removes paint from his house, destroys the paint on his car, rips shingles off the ceiling or the siding of a side of the house, and even causes serious injuries to himself or others. The marks on the pressure washer can also indicate that you're moving the nozzle too fast, which doesn't give it enough time to clean up the dirt.
If you are sure of the pressure washing skills, you can change the tip of the nozzle to a much wider one and go over the concrete again. Pressure washing, by itself, isn't the problem; the problem is that it's very easy for an inexperienced owner to choose the wrong nozzle, use a higher pressure than they should, or not understand how powerful the pressurized water stream that leaves the pressure washer can be. If you use pressure higher than this, it can be risky, especially if the concrete is weak or not in good condition. When washing pavers, bricks, or concrete under pressure, these errors can cause visible damage, such as bites, lines, or general surface degradation.
Fortunately, this is easily achieved by following pressure washing best practices, as mentioned in the instructions section. It's easier for someone who pressure washes on a daily basis to know precisely how to clean their surfaces without causing any damage. Before starting the cleaning process, take a close look at the surrounding surface around the concrete you want to wash. If the concrete was damaged during the pressure washing process, repairs will depend on the severity of the damage.
