The snowbanks are finally gone, and the driveway looks like it lost a fight. White crust from a winter of salt, a fan of plow sand across the apron, a dark spot where the truck drips, and a sprinkle of orange dots from last fall's fertilizer.
Most of that comes off with water, a brush, and some patience. A few stains need a specific cleaner. And a few problems only show up once the dirt is gone.
Pick the Right Week
- Wait until salt season is really over. Wash in March, salt again for an April snow, and the crust is right back.
- Check the overnight lows. Water soaks into joints, cracks, and the top of the concrete. If it freezes that night, you've handed freeze-thaw a fresh start.
- Plan ahead if you want to seal. Sealers need a dry slab and a minimum temperature, so wash at the start of a mild, dry stretch.
In northeast Wisconsin, late spring and early fall are the sweet spots.
Start Dry
Shovel and sweep the plow sand off first. Sand plus a pressure washer is a muddy sandblaster. Pull weeds out of joints by hand, because blasting them out takes the joint filler with them. Then move the cars and note the oil spots while they're easy to see.
Salt Crust and Road Grime
That white haze is dried deicer brine mixed with grit. Calcium chloride, a common deicer, pulls moisture out of the air, so leftover residue tends to stay damp and grimy long after the snow is gone.
Plain water does most of the work. Soak the driveway for a few minutes, scrub the worst areas with a stiff push broom and a little mild detergent, and rinse well. The first few feet outside the garage door usually need a second round.
Skip acid here. Strong acids etch concrete and keep working until they're rinsed off, and the surface has had a hard enough winter.
The street apron takes the worst of it
The apron, between the sidewalk and the street, catches everything the plow throws: salty slush, sand, and road grime. Give it an extra scrub.
It's also worth knowing who owns it. Green Bay counts driveway aprons as public right-of-way, and repair work there requires a city-licensed contractor and a permit. Cleaning is your call, but if the apron needs repair, check your municipality's rules first.
Spot-Treat Stains Before You Wash
A pressure washer alone rarely pulls out set-in stains. Treat them first, then wash everything so it dries to one color.
| Stain | What it is | What works | What to skip |
|---|---|---|---|
| Oil drips | Motor oil soaked into the pores | Fresh: clay absorbent, sweep, then degreaser and a stiff brush. Old: repeat, or use a poultice. | Gasoline or other fuel as a cleaner. It's a fire hazard. |
| Tire marks | Plasticizers that migrate out of warm tires | Degreaser kept wet while it dwells, scrubbed, then rinsed | Cranking up the pressure, which can etch around the mark |
| Orange rust specks | Iron in lawn fertilizer that got wet on the slab | An oxalic acid rust remover (often sold as wood bleach), per the label, with gloves and eye protection, rinsed thoroughly | Muriatic acid except as a last resort. Bleach, which doesn't remove rust. |
| Green or black film | Mildew or algae on shady sections | Detergent scrub and rinse | Mixing bleach with other cleaners |
- Old oil may leave a shadow. It often lightens a lot without disappearing. See cleaning oil off concrete.
- Oxalic acid is poisonous and corrosive, and it can burn grass. Wet down nearby plants and keep pets and kids clear until it's rinsed. More in removing rust from concrete.
- Prevent the next round. After fertilizing, sweep the granules off the driveway before rain or the sprinkler hits them.
Keep cleaners out of the storm drain. Rinse water with degreaser, acid, or bleach in it shouldn't run to the curb, and many Wisconsin communities ban putting anything but stormwater into storm sewers. Use only what the label calls for and follow its disposal directions. And never mix bleach with ammonia (toxic chloramine gas) or with acids like rust removers (chlorine gas).
Pressure Washing Without Stripes
Use a surface cleaner on the flat. It's the round, hooded attachment with spinning nozzles inside. It holds the nozzles at a fixed height over a wide path, so you get an even finish instead of wand streaks. Check that your machine meets the cleaner's pressure and flow minimums before you rent one, and save the wand for edges and corners.
On a wand, pick a wide tip. Tips are color-coded by spray angle: red is 0° (a pencil-thin jet), yellow 15°, green 25°, white 40°, and black is the low-pressure soap tip. Leave the red tip in the box. A narrow jet etches concrete and leaves permanent lines. Green or white handles a driveway.
Find your working distance. Start about two feet off the slab and move in only until dirt starts lifting, usually around 12–18 inches. If the jet is cutting a lighter line into the surface, back off.
Know why stripes happen. A stripe is a pass that got a different dose than the one beside it: the wand dipped lower, your arm slowed down, or the passes stopped lapping. Pick a pace you can hold for the whole driveway and lap each pass a third to half over the last. Let the slope set your starting point, usually the garage end, so the runoff carries loosened grime onto concrete that still needs washing.
Don't blast the joints. Aim a wand straight down into a joint, or trace along it, and you can blow out the caulk, the old filler strip, and the sand under the slab edge. Rinse joints at a low angle and keep moving. If the sealant is already loose or missing, that's a repair item, not something to clean out at full pressure.
When to Seal After Cleaning
Right after cleaning is the best time to seal, just not the same afternoon.
- Let it dry through. Concrete can feel dry while the pores are still wet. On the penetrating sealers we checked, the wait after washing ranged from a few hours to a full 24. In cool Wisconsin weather, we'd give it at least a full day of dry weather.
- Check the temperature window. Label minimums we saw ran from 40°F to 55°F, never on frozen concrete, with no rain for several hours after.
- New concrete waits. Labels commonly say 28 days of curing first. A few allow 14.
- Fix joints and cracks first. Sealer makers want caulk and patches in place and cured before a penetrating sealer goes on, and sealer won't keep water out of open joints or cracks anyway.
For most Wisconsin driveways, a breathable penetrating silane or siloxane sealer is the go-to. It soaks in, leaves no slippery film, and helps the concrete shed water and salt. See why seal concrete and choosing a concrete sealer.
Doing it all at once? The order is clean, let it dry, lift any sunken sections, patch the lift holes, caulk joints and cracks, then seal once the caulk has cured.
Use the Final Rinse as a Free Inspection
Before the slab dries, take a walk. Puddles that sit mark low spots. Water running toward the garage or house means a slab has tipped the wrong way. Lines that stay wet longest often trace cracks and open joints.
| What you find while cleaning | What it usually means | The fix |
|---|---|---|
| Thin cracks, flat on both sides | Shrinkage or minor movement | Often nothing, or flexible caulk. See concrete crack types. |
| A crack with one side lower | Part of the slab lost its support | Lift the low side, then seal. See driveway crack repair. |
| Empty, crumbling, or weedy joints | An open path for water under the slabs | Backer rod and flexible sealant. See filling expansion joints. |
| A widening gap at the garage or house | The slab settled or pulled away | Lift if tipped, then caulk. See caulking where concrete meets the house. |
| A section that holds water or rocks | A void under the slab | Foam lifting. See voids under concrete. |
| One edge the plow or shovel keeps catching | That slab sits lower than its neighbor | Lift the low slab flush, then caulk the joint. See how concrete lifting works. |
| Flaking or pitted surface | Salt and freeze-thaw damaged the top layer | Seal what's sound. Bad scaling needs resurfacing or replacement from a concrete contractor (not a service we offer). See concrete spalling causes. |
| Light stripes or sandy patches | Washed too close or with too narrow a tip | Permanent. Seal it and use a surface cleaner next time. |
Sunken sections are a lifting job: a few 5/8" holes (about the size of a dime), high-density structural foam that fills the voids as it raises the slab, holes patched, and you can drive on it the same day. Lifting season runs from spring thaw to freeze-up, right alongside cleaning season.
When You Don't Need Us
Salt crust, light grime, and fresh oil drips are a good Saturday project, no contractor required. Call someone when stains have been there for years, when you'd rather not rent equipment or handle acids, or when the rinse turned up sunken slabs and open joints you want fixed in the same visit as cleaning and sealing.