Soft Washing a Roof: What the Process Looks Like, Step by Step
Soft washing is the right way to clean almost any roof, but because it is less dramatic to watch than a pressure blast, people are not always sure what they are paying for. Here is exactly what a professional roof soft wash involves, start to finish, so you know what a proper job looks like.
Setup, inspection and protection
A proper job starts on the ground. The crew inspects the roof to confirm the material, pitch and how much growth there is, and checks access and safety. Landscaping around the downspouts and below the work is pre-wetted and, where needed, protected, because the treatment rinses down and off the roof.
Loose debris and heavy moss cushions are cleared first, by hand and brush where the growth is thick, so the treatment can reach the surface rather than just soaking into a mat of moss.
Treatment and dwell
The soft-wash solution, a biodegradable detergent, is applied evenly at low pressure across the roof. Then it dwells: it is left on long enough to kill the moss, algae and lichen down to the root. This dwell time is the part that makes soft washing work, and it is why the method is chemistry-led rather than force-led.
The solution is applied carefully so it covers the growth without pooling or running off before it has done its job, and adjacent surfaces and plants are rinsed as needed throughout.
Rinse, and the weeks after
Depending on the roof and the product, the roof is gently rinsed, or the rain is left to do the final rinsing over the following weeks. This is the part that surprises people: a soft-washed roof often keeps getting cleaner for weeks after the crew leaves, as the dead growth releases and washes away.
Because the moss and algae are killed at the root rather than blasted off, the roof stays clean for years, not months. That lasting result, not a dramatic same-day before-and-after, is the point of soft washing.