Some people just don’t’ realize what ‘a prize’ an old stone retaining walls is on their property. Instead of letting this piece of history fall into disrepair it should be maintained or even ‘spruced up’! A thorough cleaning of an old stone retaining wall can bring the wall back to life and once again add beauty to your yard and landscape.
You have to be mean to clean! – Old stone walls have years of soot and mold buildup. These stains can be tough to remove depending on how deep the mold and soot have penetrated. There can also be fungus and algae growth, as well as vines or ground cover rooting into the wall. So what to do? Well, you do realize that these parasites have to go! So let’s get out the pressure washer and prepare for cleaning!
Use a medium-size pressure washer – Is the pressure washer ready? OK good… now… STOP!! The worst thing that you can possibly do at this point is to start the pressure washer and blow out all the joints with a high-pressure spray!
In addition, if you begin to clean the wall without the proper soaking, you will only drive the surface soot deeper into the walls pores by wicking action making it harder to clean… so hold your horses! No… the approach that I’m going to explain to you is a little more subtle and softer.
Ok. Now begin the cleaning process by first saturating the wall. This is achieved by gently washing the wall down with a wide-angle nozzle. Stand back from the wall maybe 3′ – 4′ and let the water flow over, around and run down the face of the wall.
Now your wall is thoroughly soaked which will allow the detergent to penetrate deeper into the wall system lifting the soot and grime away. Also, a saturated wall will keep the detergent from drying out prematurely allowing it ample time to perform its’ function.
The trick is to use a commercial grade degreaser – Now apply a concentrated heavy degreaser purchase from a commercial pressure cleaning supply company. Do not dilute. Pour the detergent straight from the bucket into a garden sprayer and begin to spray the wall. Make sure that every inch of wall is covered and try to keep a ‘wet look’ as you go. This degreaser will cost a few dollars but this is not the place to scrimp. If you want the wall cleaned buy the degreaser… simple.
Now it looks even worse! – Ok, now the wall has been soaked and the degreaser applied, so what do you do? You wait. That’s right… you wait.
After about 10 – 15 minutes the wall will start to turn dark amber then a dirty brown. You will see streaks of grime dripping down the face of the wall. The wall will look terrible and you’ll be worried that you screw it up! That’s good. As soon as you begin to feel that it’s a hopeless cause and are ready to throw in the towel, you’ll know that your work is almost done!
Now that the degreaser has had a chance to work by lifting the grime, it is time to agitate it just like a washing machine. Using your 15-degree nozzle begins to hit the wall with quick, random strokes and from top to bottom. You are not looking to saturate the wall this time. As you see the soap suds appearing from the pressure of the spray, move up and down the wall and proceed along its’ length.
You may do this a couple of times along the length of the wall to get the deepest cleaning possible. This agitation will dilute the degreaser to a lower viscosity and create soap bubbles that will lift the surface soot and grime away.
Ok… now you can blow it away! – After the degreaser has been agitated you can now proceed to the final step of pressure washing the wall. Beginning where you first applied the degreaser you place your wand about 12″ – 16″ away from the face of the wall.
You clean by watching the soot lift from the wall as you move your nozzle from joint to joint and from stone to stone. You will see the soot and grime lift away as you proceed down the wall. If a section, further along, looks like it is drying out too quickly then agitate again, to keep it wet until you can reach that section.
You will be amazed by how quickly years of soot, grime, mold, and debris wash away. Areas with stubborn stains may require another application.
When you have finished you will step back in amazement! That old dingy wall will look new and refreshed and your job is complete. After all that hard work sits back and enjoy the beauty your restored wall provides… after all you deserve to relax!
Michael Olding is a tradesman and consultant in the field of restorations and repairs and currently operates a restoration and repair business in Cincinnati, Ohio. He is also a Master in the field of masonry construction, restorations and repairs.