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Why Fixing Your Drainage Won’t Fix Your Sunken Concrete (And Vice Versa)
Quick summary: Drainage problems and sunken concrete are two different jobs with two different fixes. Regrading your yard, cleaning your gutters, or installing a French drain will stop future soil erosion, but it won't lift a slab that's already settled. Slabjacking will lift and stabilize a sunken slab, but if there's an ongoing drainage issue underneath it, the ground can wash out again, yikes. Depending on the situation, you may need one fix or both, and sometimes lifting the concrete itself is what solves the drainage problem.
We get this question almost every week, usually from a homeowner who just paid a landscaper or drainage company a few thousand dollars and is confused why their driveway or walkway is still sunk in the same spot. Or the opposite: someone had their concrete raised a few years back and it's sinking again, and they assume the work was done wrong.
Neither is usually the case. The truth is, drainage and concrete settling are related in a lot of cases, but they're not always the same problem, and they don't always call for the same fix. After 20+ years of doing this around Western Washington, our team has learned that being upfront about that difference is what actually earns trust with homeowners, not telling people we can solve everything with one visit.
A few different jobs, a few different causes
Concrete settles for a handful of reasons, and drainage is a big one, but it's not the only one. Our soil in the PNW, especially the glacial till and clay-heavy pockets common from Everett down through Tacoma, doesn't drain evenly, and water pooling against a foundation or along a slab edge is a common culprit. But we also see plenty of settling from poor initial compaction under the slab, loose or improperly compacted backfill, general soil disturbance from construction or landscaping, natural erosion over time, and things like tree roots disrupting the soil structure. Sometimes it's one of these on its own, and sometimes it's a combination.
A drainage contractor's job is to redirect or manage water so it stops causing erosion. That might mean regrading the yard so water flows away from the house, extending downspouts, installing a French drain, or fixing a clogged or crushed drain line. When drainage is genuinely the issue, that's real, important work, and we recommend it often.
But if the settling isn't a drainage issue in the first place, no amount of regrading or French drains will fix it. And even when drainage was involved, once soil has washed out or shifted under a slab, addressing the water source doesn't refill that void on its own. That's a structural problem at that point, and it needs a structural fix.
That's where slabjacking comes in. Slabjacking is the process of injecting polyurethane beneath a sunken slab to float it back into place, filling the void and restoring support under the concrete. If there's an unresolved drainage issue contributing to the settling, it's worth knowing that going in, since that same area could see erosion again down the road if the water isn't addressed. We've seen it happen, usually a couple years down the road, in almost the exact same spot.
"We'll get a call from a homeowner who's frustrated because they raised a walkway with us three years ago and it's dipping again in the same corner," says Israel Craig, a Lead Field Advisor at 1-866-SLABJACK. "Sometimes when we dig into it, there's a downspout dumping water right at that corner, or the grading pushes water back toward the house instead of away from it. Other times it's just settling in a different section of the same slab, which isn't a drainage thing at all, just how the ground under that area is behaving. Part of our job is figuring out which one we're actually looking at."
Why the order isn't always the same
When there's a clear, active drainage issue, it's usually smart to handle that alongside or before the concrete work, since raising a slab over water that's actively eroding the soil underneath it can mean dealing with the same settling again later. Think of it a bit like patching a leaky roof from underneath without fixing the leak itself. It can hold for a while, but the root cause is still there.
That said, drainage isn't always the root cause, and it's not always a separate job. In a lot of cases, a slab settles unevenly and that unevenness is what's actually causing water to pool or run the wrong direction in the first place. Once we lift and re-level that slab, proper slope is restored and the water starts draining the way it's supposed to again. In those situations, slabjacking is the drainage fix. There's no separate project needed.
This is exactly why we don't lead with a one-size-fits-all answer. During a free inspection, our team looks at the settling itself, the surrounding grading, downspout placement, and any signs of standing water, and that combination tells us whether we're dealing with a straightforward lift, a lift that will also correct the drainage, or a situation where a separate drainage fix makes sense too. You can read more about how the Puget Sound climate affects concrete sinking and settling on our site, and we've also written about how seasonal cycles in this region affect slabs if you want to dig deeper into the "why" behind all of this.
Our warranty is actually part of how we diagnose the problem
Here's something most homeowners don't realize: our one year, no questions asked warranty isn't just a nice perk, it's actually a useful diagnostic tool in itself. If a slab settles again due to soil compaction shortly after we've lifted it, that almost always shows up within the first few weeks, not years later. That's simply how compaction works. It's why we stand behind the first year completely, no questions asked.
If instead a slab starts dipping again a year or two down the road, that's usually a different story. It can point to a few different things: an ongoing drainage issue that was never fully resolved, natural soil shifting, or groundwater conditions changing with the seasons. Water and soil don't stop moving just because we've done a great job lifting your concrete.
This is actually one of the more honest things about our industry that doesn't get talked about enough. Concrete around a home in this climate is, to some degree, a maintenance item, not a one-and-done fix. Soil shifts, groundwater patterns change, drainage systems age or get overwhelmed by heavy rain years, and older backfill can settle further over time. We'd rather set that expectation clearly upfront than have someone assume their slab should never move again after one repair.
What this looks like in practice
A few common scenarios we run into:
A driveway settling near the street where a downspout has been draining directly against the slab edge for years. Here, we'd recommend extending or redirecting the downspout before or alongside raising the driveway.
A basement floor with a slow, uneven settlement, sometimes tied to grading around the foundation and sometimes just to how the original slab was compacted.
A sidewalk or walkway that's settled unevenly with no real water source nearby. In these cases, lifting and re-leveling is often the whole fix, and there's no separate drainage project needed.
A slab that dips every winter after heavy rain but seems fine in summer. This pattern is a strong sign of an active drainage path issue, and it's worth having someone look at the surrounding grade before just re-raising the concrete again.
The whole picture is important
We'd rather be the company that tells you exactly what's going on, whether that means "this one's just a lift" or "you'll probably want a drainage fix alongside this," than the one that gives the same answer to every homeowner. It's also why we get asked a lot whether polyurethane foam handles wet or saturated soil conditions better than old-school mudjacking, which is a fair question given how much rain we get here, and one we've answered in detail on our poly vs. mudjacking page.
If you're not sure what's causing your settling, that's exactly what a free inspection is for. We'll tell you straight what we're seeing and what, if anything, needs to happen alongside the concrete work.
Helpful FAQ About Drainage & Slabjacking
Does drainage always need to be fixed before slabjacking?
Not always. In some cases the settling itself is causing improper slope, and lifting the slab restores proper drainage on its own. In other cases, an active drainage issue is contributing to the settling and is worth addressing separately. Our team can tell you which situation you're in during a free inspection.
Can slabjacking fix a drainage problem?
Sometimes, yes. If a settled slab is causing water to pool or run the wrong direction, lifting and re-leveling it can restore proper slope and solve the drainage issue at the same time. In other cases, a separate drainage fix is genuinely needed alongside the concrete work.
Will my concrete sink again if I don't fix drainage first?
It depends on the cause. If an active drainage issue contributed to the original settling and it's not addressed, that area can be more prone to settling again over time. If the original cause was compaction or something unrelated to water, drainage isn't typically the deciding factor.
What does the one year warranty actually cover?
Our one year warranty covers settling caused by soil compaction, which is the kind of settling that shows up shortly after the work is done, not years down the line. If your slab settles again well outside that window, it's usually a sign of a separate factor, like an ongoing drainage issue or natural soil shifting, rather than a compaction issue.
How do I know if my sunken concrete is a drainage issue?
Some signs point more toward drainage, like settling that gets noticeably worse after heavy rain, standing water near the slab, or downspouts draining directly onto the concrete. Other signs, like a slab that's been slowly uneven for years without a clear water source, often point to compaction or soil settling instead. Our team can help you tell the difference during an inspection.
If you're dealing with a sunken driveway, walkway, or basement floor and aren't sure what's causing it, get in touch and we'll take a look, no pressure, no upsell, just an honest read on what's going on underneath your concrete.
