Moss can grow on any surface that is moist, shady and humid. While it’s an attractive feature of shade gardens, the presence of moss on a cement patio, siding, roofing or a home’s foundation generally indicates a problem. On a patio, it causes slips and falls. On a roof or siding, it’s a sign of serious water saturation and possibly the need for expensive repairs.
It’s a good idea to investigate underlying conditions before using a pressure washer to remove moss. Pressure washing may not be the best solution for moss on wooden siding because water can be forced between boards where it collects and causes more problems.
That said, pressure washing can be done in a single day, and the results can last for a year or more. Homeowners may wish to do it themselves with a rented unit, or they can hire a service to do it for them. Renting may be preferable for pressure washing if you have plenty of time to spare and are a do-it-yourself type of person. There’s a wide selection of units for rental that usually require professional experience to get the right tool for the right job. Smaller units have the hose connected directly to the mower and are good for smaller jobs. Belt-driven units are available for whole-house pressure washing. Some units have chemical solutions that add detergents and herbicides for extra cleaning power and moss prevention. Choose the right-sized unit for the job at hand. While the cost of renting a pressure washer is reasonable, at about $50 to $75 per day in most areas you have to factor in cleanup time, chemicals, etc. before you can reasonably say that having a pressure washing company come out is not your best solution.
Hiring a contractor costs a little more, but is advisable, especially if the moss to be removed is on a peaked roof where a slip or fall can cause serious personal injury. These contractors should be fully trained, well-equipped, bonded and insured for the homeowner’s protection as well as their own.
After pressure washing, take steps to remove the conditions that allowed the moss to grow in the first place. Cut back tree limbs and bushes that block direct sunlight and reduce air circulation. Repair damaged or saturated roofing and siding, or dry, paint and seal it properly. These measures will improve property value and keep moss from becoming a recurring problem.