What is that on my house?

What it actually is

Not dirt and not mold. It's a living cyanobacteria that feeds on the limestone filler in asphalt shingles and makes a dark pigment to shield itself from the sun — that pigment is the stain. It spreads by airborne spores, which is why half a street streaks the same way, and it washes downhill with the rain, which is why it always runs in streaks instead of patches.

Is it hurting your house?

Yes — it's doing damage. It holds moisture against the shingles and its dark color absorbs heat, and both work against the roof over time. The more immediate cost is that it makes a perfectly sound roof look finished — which is how people end up being sold a replacement for a roof that is fine underneath the stain.

Can you do it yourself?

No — this is where DIY goes wrong. This is the one to be firm about, whoever offers. Pressure washing a roof strips the granules that protect the shingles and shortens its life — the Asphalt Roofing Manufacturers Association specifically calls for low pressure. A store-bought spray like Wet & Forget does genuinely kill it, but by design it leaves the dead growth up there for wind and rain to wear off over the next three to twelve months. If you want it gone before an event next month, it won't do that.

What we charge to remove it

from $399 flat-quoted before we start · nothing owed to ask

What it actually is

Moss is a plant — a different organism from the bacteria behind the black streaks, and a different fix. It builds in thick mats wherever the roof stays shaded and damp, which in West Michigan is almost always the north-facing slope and anything under tree cover.

Is it hurting your house?

Yes — it's doing damage. The mats hold water against the shingles, and staying wet is what wears a roof out early.

Can you do it yourself?

No — this is where DIY goes wrong. Scraping or blasting moss off shingles tears away the protective granules and can break the seal between shingles — considerably more damage than the moss was doing. It has to be killed at low pressure, then left to dry, die and release over the following weeks.

What we charge to remove it

from $399 flat-quoted before we start · nothing owed to ask

What it actually is

It takes hold on walls that stay damp and get little sun, so the north-facing side goes first every time. It's living on moisture, pollen and the film of organic dust sitting on the siding — not on the siding itself.

Is it hurting your house?

No — it's how it looks, not damage. It isn't eating your house — that's the honest answer. What it does do is spread, and come back thicker every year until something kills it at the root rather than rinsing it off.

Can you do it yourself?

No — this is where DIY goes wrong. This is the one to be careful with. High pressure on siding drives water in behind it, blows out window caulk and lifts paint, and getting the solution strength wrong burns the plants underneath. It's the job where DIY damage most often costs more than the wash would have.

What we charge to remove it

from $299 single-story · two-story from $529

What it actually is

Pollen, exhaust film and the dirty runoff that sheets off the gutter line and down the wall. It isn't alive, it's just accumulation — and it's the main reason a house reads fifteen years older than it is.

Is it hurting your house?

No — it's how it looks, not damage. Nothing is being damaged. It is, though, the single thing that ages a house on sight.

Can you do it yourself?

Sometimes — depends on the details. It's the mildest thing on this list, and a low-pressure rinse with the right soap does move it. The same warning applies as always: never high pressure on siding, and keep the solution off the landscaping.

What we charge to remove it

from $299 single-story · two-story from $529

What it actually is

Well water and some city water carries dissolved iron. The sprinkler throws it onto the siding, brick or concrete, the water evaporates, and the iron oxidizes and bonds on as rust. It's a mineral, not a living thing.

Is it hurting your house?

No — it's how it looks, not damage. It stains; it doesn't damage. Left alone it just builds a little heavier every irrigation season.

Can you do it yourself?

No — this is where DIY goes wrong. Not with soap — nothing in the algae toolkit touches it. Iron oxide has to be dissolved with a rust-specific acid-based remover before it will rinse off. And half the real fix is free: turn the sprinkler head so it stops hitting the house, or it comes straight back next summer.

What we charge to remove it

from $179 flat-quoted before we start · nothing owed to ask

What it actually is

Concrete is porous, holds water and stays damp in shade, so algae colonizes it. The darker black-green patches are the same growth with more time on it, alongside mildew.

Is it hurting your house?

Yes — mostly as a slip hazard. The concrete is fine. The biofilm on top of it gets genuinely slick when it's wet, which is worth taking seriously if kids or anyone unsteady on their feet uses that slab.

Can you do it yourself?

Yes — this one's a fair DIY job. Flat concrete is hard and forgiving and takes pressure fine — a rented machine with a surface-cleaner attachment does a genuinely good job on a driveway or patio. Renting only goes wrong when the machine gets pointed at siding, a roof or a deck. If you'd rather not spend the Saturday, that's what we charge below.

What we charge to remove it

from $179 flat-quoted before we start · nothing owed to ask

What it actually is

Concrete is porous, so oil doesn't sit on the surface — it soaks down into it. While a spill is still wet, cat litter genuinely works, because there's liquid oil to pull back up. Once it's dried in, litter does nothing at all.

Is it hurting your house?

No — it's how it looks, not damage. It's a stain, not damage — the slab underneath it is fine.

Can you do it yourself?

Sometimes — depends on the details. Depends entirely on how old it is. Fresh, today: get absorbent on it yourself and you'll save the slab. Dried in: you're lifting oil back out of the pores, which needs a degreaser with real dwell time or heat — and that's the actual difference between a rented machine and a professional clean.

What we charge to remove it

from $179 flat-quoted before we start · nothing owed to ask

What it actually is

The same family of growth as the siding and the concrete — it just holds on harder in wood, because the surface stays damp far longer than a wall does.

Is it hurting your house?

Yes — mostly as a slip hazard. Slippery when it's wet, and it keeps moisture sitting in the boards.

Can you do it yourself?

No — this is where DIY goes wrong. Not with a pressure washer. Wood is soft — pressure fuzzes the grain and leaves stripes you cannot sand out of a whole deck. And blasting it off doesn't kill it, so it regrows from the spores left behind within weeks.

What we charge to remove it

from $149 flat-quoted before we start · nothing owed to ask

What it actually is

Sun and rain break down the surface fibers and the wood grays out. A wash and brighten pulls the color back — which is also the step that has to happen before anything gets stained or sealed, or you seal the gray in.

Is it hurting your house?

No — it's how it looks, not damage. It's the surface fibers going, not the structure. Left long enough, though, bare gray boards do start to rough up and splinter.

Can you do it yourself?

No — this is where DIY goes wrong. Not with a pressure washer, for the same reason as the algae: soft wood plus high pressure equals permanent stripes. Brightener on a washed deck is the part that actually returns the color, and it has to go on in the right order.

What we charge to remove it

from $149 flat-quoted before we start · nothing owed to ask

If it doesn't match any of the nine, we'd rather look than guess. Send a photo to 616-229-0625 — you'll get back what it is and what it would cost, and no, that isn't a trap to get you on a list.