Spring in Michigan means mud season, melt runoff, and about six weeks where every outdoor surface on your property is collecting something. By late May, most homes in Rochester Hills, Troy, and Royal Oak have picked up a season's worth of grime that rain doesn't wash off. The question isn't whether your home needs pressure washing — it's whether you're reading the signs correctly.
Here are five signals that your property is past due.
1. Black streaks on vinyl siding
Black algae, moss, or dark discoloration on siding
The dark streaks that appear near the bottom of vinyl siding in shaded areas — under eaves, on north-facing walls, near overhanging trees — are algae. It grows where moisture stays. Unlike dirt, it doesn't come off with a garden hose. A pressure wash with the right tip and detergent lifts it in one pass. If left untreated, it slowly degrades the vinyl surface and can cause discoloration that becomes permanent.
If you see dark patches on the shaded side of your house, or streaks running down from rooflines where water sheets over the siding, that's algae. Homes in Royal Oak with tree cover and older siding are particularly prone — the combination of shade and age creates ideal conditions.
2. Green or black patches on concrete, brick, or pavers
Biological growth on driveways, walkways, and patios
Concrete doesn't "fade" — it gets colonized. Moss, algae, and lichen work into the porous surface of unsealed concrete and create that green-gray look that makes a new driveway look ten years old. Driveways in Lake Orion and Bloomfield Hills with tree canopy overhead develop this fastest, but every concrete surface in Michigan is vulnerable after one wet winter.
The distinction here is sealed vs. unsealed concrete. Sealed concrete resists biological growth significantly better — if your driveway or patio was sealed when poured, you may have more time. Unsealed concrete in any Oakland County neighborhood should be pressure washed annually to prevent the surface from becoming permanently stained and to reduce slip hazard on wet days.
3. Gray, chalky areas on decks or wooden fences
Weathered, gray wood on decks or fencing
This one gets confused with "just aged wood." There's a difference between silver-gray weathered cedar that has character and a deck that's turned gray from UV damage and surface mold that's holding moisture and starting to rot. Run your hand over the surface. If chalky residue comes off on your fingers, that's a combination of UV degradation and mold — and it's a sign your deck is losing its finish faster than it should be.
Pressure washing a wood deck properly requires the right PSI and the right tip. Too much pressure on soft wood opens up the grain and creates a rough surface that holds water and stains faster than before. The right contractor will use 500–800 PSI with a fan tip and follow with a brightener if re-staining is planned. This is not a DIY task for most homeowners — get it wrong and you accelerate the degradation you're trying to fix.
4. Mold visible on gutters, trim, or fascia boards
Visible mold on exterior trim, gutters, and fascia
Gutters and fascia boards catch everything from roof runoff to pollen to bird droppings. When mold takes hold in those areas, it's not just cosmetic — it's working its way into the wood behind the trim. Fascia boards and window trim in older Birmingham and Rochester homes often have more mold accumulation than the siding itself, and it's usually hidden from ground-level view by the overhang.
If you can see mold on your gutters from the ground, call a contractor. Fascia mold is a moisture problem — the water is getting behind the trim somehow, and pressure washing the surface is the first step in addressing it. The second step is finding why water is getting behind the trim in the first place, which a good contractor will also assess.
5. Your home is about to be listed or you're getting ready to paint
You're planning exterior painting, staining, or selling
This isn't a "something is wrong" sign — it's an "optimize your investment" sign. Paint and stain adhesion depends on clean, dry surfaces. Any painter will tell you they spend time power washing before they roll on a drop of paint — because old grime, mold, and chalky oxidation create a layer between the new coating and the substrate. A professional pressure wash before painting or staining can extend the life of your new finish by years.
If you're selling in the spring or summer market in Rochester, Troy, or Royal Oak, a clean exterior makes a measurable first impression. Buyers in those neighborhoods are paying attention to condition — a freshly washed driveway, clean siding, and clear concrete walkways signal that the home has been maintained.
Timing tip for Michigan: The best window for pressure washing exteriors is mid-April through mid-October, after the ground has thawed and before the first hard freeze. Late May through September is ideal — temperatures above 50°F let cleaning agents work properly and surfaces dry before evening. Avoid pressure washing when there's frost on the ground or temperatures are below 40°F.
When to DIY and When to Hire
Rental pressure washers run $60–$120 per day. They're viable for: concrete walkways, single-story driveway surfaces, and patio pavers in direct sunlight. At those locations you can control the distance and angle without risking siding damage.
Do not attempt with a rental on: vinyl siding, wood decks or fences, anything two stories or taller, or any surface with existing damage (cracked stucco, rotted wood, loose trim). At those surfaces, wrong PSI or wrong technique causes real damage — and you're holding a machine that can strip paint, gouge wood, and force water behind siding seams in seconds.
For anything involving the house itself, the fascia, or multi-story surfaces, hire a contractor with verifiable insurance. The liability question is simple: if something goes wrong, whose insurance covers the repair?
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