When your render starts to look dirty pressure washing is usually the DIYers first attempt. “I’ll get out the Karcher and give it a blast”. Although using a pressure washer is ideal for stone and concrete surfaces, pressure washing render is not a good idea. Pressure washing rendered surfaces, such as K Rend actually strips the surface off the wall. As K Rend is only around 9mm thick, taking a few millimetres off the wall every time is is cleaned will lead to big problems. If your K Rend, Weber render, etc is pressure washed the render will become thinner which will lead to cracks forming, pieces falling off and an uneven finish.
2. Pressure washing can etch the surface
Pressure washing render with a pencil jet, or a fan jet used closely will cause etching on the render. Once your render is etched it will always show as the surface has been damaged. Although the render will likely look a little cleaner after pressure washing, it will not last. As the algae regrows on the surface the etching will be prominent. This means not only with the render be damaged, but the render will look patchy and show the lines of the etches. This only solution to etched render is to re-render the property which will come at a considerable cost.
3. Pressure washing render does not get to the ‘root’ of the problem
Through coloured renders such as K Rend, Monocouche render and Weber render all suffer with the same problems. They are a breeding ground for algae, lichen, moss and mold. These micro organisms thrive on the render and not only look bad, but also damage the surface. If the homeowner, or a company, was to pressure wash render, the roots of these micro organisms will not be killed. This means within a few months the algae, moss and bacteria will grow back.
