House washing: what a soft wash does for siding

The siding on every side, the soffits and fascia, the trim around windows and doors, and the outside faces of the gutters — the bands of black streaking that run down them are some of the most noticeable dirt on a house. The foundation and the lower courses of siding, where rain splashes mud up, get cleaned too.

Mention anything else on the call. Driveways, walks, decks and fences are separate surfaces with their own methods, but they are usually done on the same visit.

Vinyl is the most common siding in Wisconsin, and it cleans up very well by soft washing. Aluminum siding — especially the 1960s and '70s kind with factory paint — needs the gentlest hand, because the chalky surface is the paint. Steel, fiber cement and painted wood siding all clean the same way: let the cleaner do the work, then rinse.

What they have in common is that none of them should be blasted. High pressure drives water behind the laps of the siding and into the wall, and takes paint and finish off with the dirt.

Close the windows. Move vehicles, grills and patio furniture clear of the walls, and unlock any gate that needs to be opened. An outside water spigot needs to be available.

Mention anything delicate in the beds along the house, any window seals or siding panels that are already loose, and any outlets or fixtures on the outside walls that are not weather-tight.

The north side, where the green was, usually shows the biggest difference. Dead lichen and some stubborn staining can take a few weeks of weather to fully let go.

On an older house, the sunny south and west walls sometimes look more faded after a wash than before. That is oxidation — the siding's own surface wearing out — that the dirt had been hiding. The wash didn't cause it and can't reverse it. It is worth knowing about before the day rather than after.

For most houses, every year or two keeps growth from building up. Houses under trees, on a lake, or with a shaded north side usually want it more often than a house on an open lot in town. Spring and early summer book up first.