Parking lots take a beating in northeast Wisconsin. Garbage trucks, delivery vans, plow trucks scraping at 5 a.m., salt brine all winter, and snow piles that sit in the corner until April.
The concrete parts of a lot usually fail in the same spots: the panel next to the catch basin, the dock apron, the walk along the curb. And the fix usually doesn't have to be a tear-out.
Here's an honest look at what a small lifting crew can fix, what belongs with a bigger outfit, and how to keep your concrete from sinking again.
What We Take On, and What We Don't
We're a small, owner-operated crew. That's a good fit for most concrete trouble spots on a business, church, apartment, or HOA lot. It isn't a fit for everything.
| Good fit for a small lifting crew | Specialty work for larger firms |
|---|---|
| Sunken concrete parking panels and drive-lane slabs | Highways, interstates, and state roads |
| Loading dock aprons | Airport runways and taxiways |
| Sidewalks along the lot and at entrances | Large municipal street paving |
| Curb transitions and ramp landings that settled | New lots or full lot reconstruction |
| Concrete around catch basins and storm drains | Rebuilding catch basin structures or storm lines |
| Dumpster pads and drive-thru lanes | Asphalt patching, milling, and overlays |
| Joint sealing, cleaning, and sealing concrete | Asphalt sealcoating and lot-wide striping |
Right-hand column work needs paving crews, traffic control, and heavy equipment. We'll tell you that from your photos instead of taking a job we can't do right.
Why Lot Concrete Settles Around Here
- Heavy loads in the same spots. Lots are mostly built for cars, but garbage trucks, delivery trucks, and plow trucks hit the same dumpster enclosures, dock approaches, and entry drives every week. That's often where settling starts.
- Plowing. Blades chip any raised edge and scrape out joint sealant that sits too high. Plow piles stacked in the same corner add weight, then feed meltwater into the same joints all spring.
- Salt. Salt doesn't sink slabs by itself, but brine runs into open joints and cracks, freeze-thaw with salt is hard on concrete surfaces, and water that gets under a slab carries fine soil away.
- Frost. Wet soil under a slab freezes, lifts it, then thaws and leaves it sitting over a soft spot. A little worse each winter.
- Catch basin drainage. The concrete around a basin sits on backfill placed around the structure, and all the runoff in that part of the lot flows right at it.
- Clay underneath. Heavy red clay subsoil is common across Brown County. It drains slowly, so water under a slab keeps the soil soft.
Problem, Cause, Fix
| What you see | Why it happens | Fix |
|---|---|---|
| Concrete dished down around a catch basin | Backfill around the basin settles. Runoff washes soil through gaps in the structure. | Lift the panels if the basin is sound. Repair the basin first if it isn't. |
| Lip where the lot-side walk meets a curb or ramp | Walk panel settled on loose fill or washed out at the edge | Lift the low side, then caulk the joint |
| Dock apron ponding at the dock wall | Truck loads plus water collecting near the dock soften the soil | Lift the apron, then seal the joint at the wall |
| Panel that rocks, thumps, or holds water | Void under the slab from washout or frost, or the panel lost its pitch | Lift it, filling the void with foam as it rises |
| Corners breaking off along a joint | Edges cracking under wheel loads after losing support | Lift if mostly intact. Replace badly broken panels. |
| Open joints full of weeds, sand, or dead caulk | Sealant wore out, got plowed out, or was never installed | Clean out and reseal with flexible joint sealant |
| Flaking or scaling surface | Freeze-thaw and salt damage at the surface | Not a lifting job. Seal sound concrete to slow it. Resurface or replace severe areas. |
Catch Basins: The Special Case
Concrete around catch basins sinks more often than anywhere else in a lot. The backfill around the structure is hard to compact well, the soil next to it sees more water than anywhere else on the property, and when the joints in the basin's rings or the mortar around the frame break down, water flows through those gaps and drags soil in with it. That leaves a hollow under the concrete.
So before anyone lifts around a basin, look at the basin. A flashlight through the grate tells you a lot.
| If the basin looks like this | Do this |
|---|---|
| Walls and rings intact, frame tight to the concrete | Lift the surrounding panels, then seal the joint around the frame |
| Cracked or shifted rings, missing mortar, soil piled inside | Get the structure repaired first. Lifting over a leaking basin only buys time. |
| Frame and grate sunk below the concrete around them | The casting needs to be reset by a concrete or utility contractor |
Foam follows open gaps and pipes, so we plan the hole pattern around the structure and keep an eye on the inside of the basin while we lift.
Lift, Replace, or Patch?
Plenty of lots around here mix an asphalt parking field with concrete aprons, pads, and walks. Each material gets its own fix.
| Option | Works on | Good for | Watch out for |
|---|---|---|---|
| Foam lifting | Concrete | Panels that settled but are in one piece. Voids. Ponding from lost pitch. | Can't lower a heaved panel. Doesn't repair broken or scaled concrete. |
| Panel replacement | Concrete | Shattered, crumbling, or badly heaved panels. Panels that keep cracking under truck loads. | The most cost and disruption, plus curing days. A new panel on the same wet base can settle again. |
| Asphalt patching or overlay | Asphalt | Potholes, alligator cracking, dips in the paved field | A different trade. The seam where asphalt meets concrete lets water in, so ask how it'll be sealed. |
The rule of thumb: if a concrete panel is in one piece and just dropped, lifting usually costs a fraction of replacement and you're parking on it the same day. If it's in pieces, replace it. If it's black, call an asphalt contractor. For more on lifting versus tearing out, see foam concrete lifting pros and cons.
Seal the Joints Before Winter
Joints in a concrete lot are there on purpose: they control where the slab cracks. They're also where water, salt brine, and sand get in.
- Clean, dry, and warm enough. Joints have to be cleaned out, dry, frost-free, and about 40°F or warmer for sealant to bond.
- Flexible sealant, not patch. We use a self-leveling polyurethane joint sealant on flat lot joints, with closed-cell backer rod where the joint is deep. Rigid fillers crack and pop out.
- Below the surface. A bead that sits proud is the first thing a plow blade peels out.
- Coned off. Traffic stays off fresh sealant as long as its label says.
- Late summer to early fall. After any lifting, before the first hard freeze. Then walk the joints each spring once the snow piles melt.
More on sealant types and backer rod: best concrete crack caulk.
Cleaning and Sealing Lot Concrete
Walks, aprons, and drive-thru lanes collect oil drips, rust stains, and mildew in shady corners. Pressure washing takes them off, but too much pressure or the wrong tip etches stripes into the concrete. A rotary surface cleaner gives a more even result than a wand alone.
A parking lot is built to send everything to its catch basins, wash water included. Storm drains generally carry water toward local streams and the bay, not a treatment plant, and many Wisconsin communities prohibit putting anything but stormwater in them. Whoever cleans your lot should have a plan for protecting the inlets when cleaners are involved.
Once the concrete is clean and dry, a penetrating silane or siloxane sealer cuts down how much water and salt brine it soaks up, without leaving a coating for tires and plows to wear off. New concrete has to cure first; product labels range from about a week to a month.
On a combined job, the order is: clean, let it dry, lift, patch the holes, caulk the joints, then seal once the caulk has cured.
Accessible Parking and Routes
The 2010 ADA Standards don't allow changes in level in accessible parking spaces or access aisles other than slopes no steeper than 1:48, about 1/4" per foot. A settled panel in an access aisle can push it past that, and a dropped walk on the route to your door can leave a lip over the 1/4" limit. Lifting can often bring both back in line. Our ADA sidewalk requirements guide has the numbers and how to measure them.
Keeping the Lot Open
We work in sections, with cones around the slabs we're lifting, and the rest of the lot stays open. Lifted concrete takes foot traffic right away and cars the same day. Off-hours starts can be arranged for drive-thrus, docks, or entrances that can't be blocked.
Quick Self-Check After the Next Rain
Walk the lot an hour after a good rain, and look for:
- Puddles on concrete, a sign a panel lost its pitch
- A sunken ring around a catch basin, or a gap at the frame
- Panels that rock or thump under a car
- Wide joints, weeds, or sand washing out
- Lips over about 1/4" on walks to the door
Photograph each spot with a tape measure in the frame, and your quote request is mostly done.