Stucco has become a much more reliable siding material since the advent of synthetic stucco materials on the market. There are many home building situations where the look and feel of stucco is going to be a much more artistic surface for that particular home. Now if you want the stucco to be a certain color you can simply mix the tinting agent into the stucco when you are blending it with water. Synthetic stucco is still cement based but there are newer high tech additives which make it stronger and also more water resistant.
In order to understand the proper ways to clean stucco walls it is very helpful to know how stucco walls are assembled first. Stucco is able to be applied over any substrate the will allow the stucco material to adhere to it. This usually calls for some sort of porous openings in the substrate to allow the stucco to lock into the base material. Stucco can be applied directly over concrete and it can also be applied over wood providing you first apply felt backing paper and then a layer of chicken wire with the proper spacers to leave a gap between the felt and the screen. This layered assembly is for the scratch coat of stucco to go into the wire mesh and not into the wood below the felt.
Once the scratch coat of stucco is finished this wire mesh is permanently embedded inside the stucco and a finish coat is then applied over the first “scratch coat” layer. This is where cleaning stucco becomes an issue in that if you overwork the stucco then you can break away the laminate layer that is on the outside surface of the stucco if you are too aggressive and are not careful.
The best way to wash your stucco walls is to use warm water with a few household chemicals in small doses scrubbing with a soft bristled brush and a bit of elbow grease. First you need to prepare the work area by covering any plants that may be harmed by contact with the two chemicals we are going to use using plastic sheeting that can be rinsed and reused or thrown away. Next get your ladder(s) in place and put your safety gloves and glasses on. Next mix up a gallon at a time of the following cleaning solution: one cup of trisodium phosphate (TSP) and 1 ounce of bleach in one gallon of warm water.
You may be saying to yourself what is this TSP chemical; is it safe and where do I get some? Well TSP is a widely used cleaning chemical that comes in powder form which is safe to use providing you follow all precautions on the container and it is easily found at your local home improvement store or any decent hardware store as well. Since we are using some bleach as well you may want to find a hidden spot on your stucco to see if the color will change dramatically once you wash the walls with this solution. Cut the bleach down to 1/4 cup if it seems too strong. Or you can dilute the entire gallon into two gallons by just making up the difference with another gallon of water.
Next use your garden hose to very lightly wet the area you are going to clean starting at the top and working your way down. Please do not use high pressure from a pressure washer as this may be more harmful to your stucco than helpful. Only wet and wash a strip wide enough that you can stop and rinse it immediately before it dries out as this will help you maintain a uniform color across the entire cleaned surface. You want to do at least a two foot wide patch so that you can scrub the area top to bottom in two minutes. Once you have scrubbed a two foot wide area using a soft bristled brush and then use the garden hose to gently but thoroughly rinse away the cleaning solution. If you get some on your plants then super soak them to wash away and dilute the cleaning juice that escaped.
Once your first area begins to dry step back and decide if you need to wash each area once or will a second scrubbing be required? Remember to scrub gently and if you clean the walls and are still not happy with the results you can either purchase higher power cleaners for big bucks or you can go ahead and prepare to paint your stucco walls to make them look like new.