Your siding is a shade lighter than you think.

What builds up on siding

Green film on the north wall. Gray dirt streaks under the gutters. Black spots on the soffit. Cobwebs in every corner and a wasp nest behind the shutter. It builds up slowly enough that most people stop seeing it — until the neighbor gets theirs washed.

Almost all of it is organic: algae, mildew and pollen bonded to the surface, plus road dust and whatever the gutters overflowed. Rain doesn't remove it. It feeds it.

How we wash a house

Siding gets soft washed, same principle as a roof. Low pressure, cleaning solution, dwell time, rinse. High pressure on vinyl can force water behind the panels and into the wall, and on older painted wood it can take paint with it. There's no reason to risk either when the solution does the work.

• Windows and doors checked, hose bib located, landscaping pre-wet
• Solution applied from the bottom up so it doesn't streak
• Siding, soffits, fascia, gutter faces, porch ceilings and shutters
• Rinsed top down, plants rinsed again
• Walk-through before we leave

What it does for the house

• Gets the actual color of the siding back
• Clears mildew and algae growth rather than just wetting it down
• Makes a real difference in listing photos if you're selling
• Takes down cobwebs, dirt daubers and nests along the eaves

Most people book house washing with a roof cleaning and a driveway cleaning in the same visit.

How often should a house be washed?

For most Upstate homes, somewhere around every year or two. What actually decides it is the house, not the calendar — a north-facing wall under trees picks up growth far faster than a sunny elevation with nothing shading it.

The usual sign is that one side of the house no longer matches the others. If you're squinting at a wall trying to work out whether it's dirty or just the color it has always been, it's dirty. Send us a photo and we'll tell you whether it's worth doing yet.