Cleaning the walls: how to clean retaining wall blocks

Retaining walls are often meant to be both decorative and practical, and when they look good they can add a great deal of curb appeal to your garden or patio. The only problem is that any retaining wall will eventually accumulate dirt, mold, plant material, and various types of dirt that can leave the blocks looking stained and ugly. Fortunately, re-cleaning the blocks is relatively simple, and with the right tools and a little attention to detail, any stained or dirty retaining wall can be restored to its former glory.

Part of what you need to keep in mind before trying to clean a wall or some blocks is that the method you should use depends on the material of the wall. If it’s an old stone wall that has been standing for decades or more, or if it’s made of prized old bricks, it’s a bad idea to shoot with guns and ruin the wall by using harsh chemicals or the wrong cleaner. Also, if you do things the wrong way, you can sink the dirt deeper into the blocks and make the whole job more difficult. Think carefully before taking out the pressure washer!

The best place to start, no matter what your retaining wall blocks are made of, is with an ordinary garden hose with a spray attachment. (You’ll need the type that has a reservoir that allows you to add cleaner to the sprayer.) Start by lightly spraying the entire wall or blocks that need to be cleaned. The entire area should be soaked so that when you go to clean up the dirt, there is no absorbent action drawing the moisture (and dirt) into the blocks or into the wall.

Consider whether or not the wall is in an area where you need to protect vegetation. If you’re concerned about runoff from the cleaning process, especially if you’re going to be using some kind of harsh stain removal product, then you should consider putting down tarps or plastic drop cloths to protect plants from the brunt of the runoff. .

Here are the basic cleaning options:

* If you are cleaning a stone retaining wall, invest in a professional grade degreaser and put it directly into the reservoir of your garden hose sprayer. Soak the entire area to be cleaned and wait ten to fifteen minutes for the degreaser to take effect. (As a result, the wall will most likely look dirtier than before.) After you wait, take an electric sprayer and spray down the wall, working from top to bottom and from one side to the other. Keep it like this until the wall stops foaming. Then let it dry.

* If you are cleaning a retaining wall made of bricks or concrete blocks, start by using a little regular dish soap in your garden sprayer. Using a dish soap solution and a toothbrush, carefully scrub the stained areas. Spray the soap with an electric sprayer and allow the wall to dry.

* If you’re cleaning cinder blocks and soap doesn’t remove stains or dirt, fill the garden sprayer attachment with bleach. (Remember to take proper safety precautions, wearing goggles or safety glasses and appropriate clothing.) Spray the wall with bleach, as above; then let dry.

* If none of these options work, there is hydrochloric acid. It can be effective for stain removal on some types of block, but it is too harsh to use on all materials. If you must resort to using hydrochloric acid, be sure to follow the manufacturer’s instructions exactly, or consider bringing in a professional who can safely work with this type of hazardous substance.

Ultimately, most dirt and stains on retaining wall blocks aren’t that difficult to remove, and the average homeowner should be able to get the job done. Just remember that you should never start out using a pressure washer, and that powerful chemicals and cleaners should be used with an appropriate level of caution.