The slab sounds different before it sinks
Walk your driveway or garage floor with a steel rod, tap as you go, and listen. A solid thud means soil is bedded under the slab. A hollow ring means there's nothing under that spot but air. That hollow spot is a void, and in Arvada we find them constantly, because this city's clay is cut by the Ralston Creek and Van Bibber drainages and its older neighborhoods spent decades letting roof water pour out beside their slabs. Washout under concrete is the routine call at our shop, and since the shop is on Russell Court, these are our own neighborhoods we're talking about.
Where Arvada's missing soil went
A void means soil left. Around here it leaves three main ways:
- Downspout washout. The classic Arvada version. An older downspout setup discharges at a slab edge, and every storm since the house was new has carried a little more base material away with it.
- Drainage-side soil movement. Lots near the creek corridors see more subsurface water on the move, which keeps fine material migrating out from under concrete year after year.
- Shrinking clay. Wind off the foothills dries this ground hard between storms. Dry clay contracts and drops away from the slab bottom, and the gap it leaves doesn't close back up when the moisture returns.
The concrete bridges the gap for a while. Slabs are good at that, right up until a delivery truck parks on the unsupported span, or a spring melt fills the pocket with water and softens the edges holding everything up.
Filling the pocket before the concrete follows it down
Void fill is prevention, which makes it different from every other service on our truck. The slab is still at grade; our job is to put support back underneath it before gravity gets a vote. We drill the same 1.5" holes we'd use for a lift, pump the same Portland cement, sand, and topsoil mix, but at low pressure, packing the cavity solid without moving the slab at all. Half a day on site, back in service the same day, and the cured material ends up harder than the clay it replaced, so the pocket doesn't reopen.
Catching the problem at this stage is the whole game. Filled now, it's a modest line item. Ignored until the slab drops, it becomes a leveling job. Ignored past that, it can become a replacement. Most Arvada void-fill work runs $400 to $1,500, quoted by the volume of the cavity, and every job in that range is cheaper than the repair it prevents. The truck holds 10 yards of material, so even a large cavity gets packed in one continuous pump instead of waiting on refills.
The calls that bring the rod out in Arvada follow a pattern: a soft or sunken feel along a slab edge, a sprinkler line repaired near the driveway, a hollow note under the garage floor during a pre-sale inspection, or utility work that left loose trench backfill running under a walk. Any one of those is worth thirty seconds of tapping before it becomes a repair budget.
Spring melt is the deadline
Arvada's upslope snow seasons matter here more than most people realize. The heavy, wet storms of March and April melt off fast, and meltwater pours into any cavity it can reach. A water-filled void softens the soil at its rim, grows itself larger, and sets the slab up to drop exactly when the ground is at its weakest. If you heard a hollow tap last fall, get the pocket filled before the storms stack up. We work through winter; the mix cures fine in cold weather, and only ground frozen rock-hard delays the drilling, usually by a day or two.
A thirty-second test and a straight answer
Every AAA estimate includes the tap test, free. Trevor walks your slabs with the rod, marks the hollow spots, and tells you plainly which of three answers you've got: a void worth filling, a slab that's already dropped and needs a lift, or nothing wrong at all. That third answer gets given more often than you'd think. We can afford the honesty; we've been Arvada's hometown concrete-raising outfit since 1988, and repeat neighbors are the whole business model. For the deeper background, read how voids form under concrete, or go straight to booking your free estimate. Call (303) 526-2222 and we'll bring the rod.