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cleaning brick retaining walls – Why is using hot water, cleaning solutions and low pressure the best way to clean brick walls?

A client asked me today why do we have to use “pressure washing chemicals” when we are cleaning brick retaining walls.  He said that he normally cleans them himself with his cold water pressure washer, so he asked me if we could clean them the same way.  I know that a lot of people think that it’s best to avoid using any chemicals these days to protect the environment, the problem is that if you don’t use some type of cleaning solution, your not really getting the surface as clean as you think.

pressure washers can cause damage

Most pressure washing companies use cold water pressure washers and up to 4,000 PSI to clean concrete, siding, roofs and brick walls, which can easily damage the surface. The photo to the left shows damages caused to concrete.

Now I’m not saying that it is impossible to clean brick walls with just cold water, but hot water pressure washing equipment and detergents will do a much better job.  The best way I have found to describe it is like this:

Let’s say you had a nice steak dinner, with a baked potato and a salad.  Now when you wash the dishes in your sink, you can get them clean if you use a scrubby sponge, but your not disinfecting them, or removing the oils from the food, so bacteria, mold, mildew and grease/oil will still be on the dishes.

If you add soap, it will remove the grease/oils, bacteria, mold and mildew, and it’s easier and faster to clean them.

Now, use hot water and soap, and the dishes come clean much faster, the hot water will easily melt away the food grease/oils, and the soap will remove the bacteria, mold and mildew.

Now on the brick walls you have mold, mildew, Gloeocaspa Magma ( A type of Cyanobacteria) and hydrocarbons from airplanes, cars etc.  (Hydrocarbons are basically like grease and food oils).  That’s why the best way to clean them is by using a soap and hot water.  It cleans the brick walls faster with less pressure, and it’s a deeper cleaning that you would get from a cold water machine.  When you just use cold water and pressure, it will “blast off” the mold, mildew and Gloeocaspa Magma, but it doesn’t remove the small tiny root system that’s growing into the brick, so the mold and mildew will just grow back again fairly quick.  The cleaners we use are applied at only 40PSI or so, then we let them sit on the wall so that they will break down the Hydrocarbons and dirt on the walls, break down the tiny root systems from the mold, mildew, Gloeocaspa Magma, Lichen and then break them loose from the walls which allows us to use less pressure to wash the walls.