Commercial Services
FILLFOAM™ Void Filling Services
When the Ground Disappears — We Fill It Back In.
Seattle's Trusted FILLFOAM™ Void Filling Experts
Your concrete can look perfectly fine on top while a completely different story is playing out underneath. Soil shifts, water erodes, and over time the ground beneath your slabs quietly disappears — leaving voids that put your concrete, your foundation, and your property at real risk. At 1-866-SLABJACK, we use FILLFOAM™ — a professional-grade, pre-expanded open-cell polyurethane foam — to fill those hidden voids fast, stabilize the ground below, and stop the problem before it becomes an expensive disaster. No heavy equipment. No digging. No days of downtime. Just solid results.
WHAT IS FILLFOAM™?
FILLFOAM™ is not your average foam. It's a specially formulated, pre-expanded open-cell material engineered specifically for void filling applications — which means it's different from the polyurethane foam we use for lifting and leveling concrete slabs. Where slab-lifting foam is designed to expand aggressively and generate upward pressure, FILLFOAM™ is designed to fill — flowing into irregular underground spaces, conforming to cavities, and curing in place without exerting excessive pressure on surrounding structures.
Key characteristics of FILLFOAM™:
- Pumped at full volume — it does not lose volume when cured in a confined space
- Lightweight: approximately 2 pounds per cubic foot — no added load on weak or compromised soil
- Waterproof and moisture-resistant — won't break down, wash away, or degrade over time
- Fast-curing — minimal downtime for your property
- Permanent — once it's in, it stays in
Think of it as a foundation for your foundation.
WHY VOIDS ARE A SERIOUS PROBLEM IN THE PACIFIC NORTHWEST
Western Washington homeowners and business owners deal with a soil and climate environment that is particularly hard on concrete. Our wet winters, clay-heavy soils, and the natural movement of water through the ground make void formation more common here than almost anywhere else in the country. Here's how it typically happens:
Erosion & Washout: Heavy rainfall — and we know a thing or two about that around here — gradually washes fine soil particles out from beneath slabs and foundations. Over time, small openings become large voids.
Soil Settlement & Compression: As soil compresses or shifts under load, gaps form between the ground and whatever structure sits on top of it.
Utility Line Failures: Leaking water lines, failed drain pipes, or aging sewer lines can erode soil from the inside out, creating large underground cavities you'd never suspect are there.
Tree Root Activity: As tree roots grow and eventually die or are removed, they leave behind channels in the soil that collapse into voids beneath your concrete.
Poor Original Compaction: When soil wasn't properly compacted at the time of construction, it continues to settle for years — leaving your slabs slowly losing the support they were built on.
Left alone, voids grow. And when they grow large enough, the concrete above them doesn't have the support it needs — leading to cracking, sinking, settlement, and in serious cases, sudden collapse.
WARNING SIGNS YOU MAY HAVE VOIDS BENEATH YOUR CONCRETE
Not sure if voids are a problem for you? Here's what to watch for:
- Concrete that sounds hollow when you walk on it or knock on it
- Slabs that have cracked, tilted, or sunk — especially recently or after heavy rain
- Doors or windows that have started sticking or binding (potential foundation void activity)
- Visible gaps between your concrete slab and the soil, trim, or adjacent structures
- Pooling water that seems to "disappear" rather than drain properly
- Concrete that shifts or flexes underfoot
If any of these sound familiar, don't wait. Voids don't fix themselves — they only get bigger.
HOW FILLFOAM™ VOID FILLING WORKS
Our void filling process is fast, minimally invasive, and uses no heavy equipment. Here's what to expect when the 1-866-SLABJACK crew shows up:
Step 1 — Assessment & Planning Every job starts with a thorough inspection of the problem area. Our experienced technicians evaluate the extent of the voiding, identify the likely cause, and determine the injection points that will give us the best foam distribution beneath the slab.
Step 2 — Strategic Drilling Small injection holes are drilled at targeted locations in or around the concrete. These holes are modest in size — similar in scale to what you'd see in our polyurethane slab-lifting work — and are placed to maximize material reach into the void.
Step 3 — FILLFOAM™ Injection FILLFOAM™ is pumped through the injection ports at full volume. Because it is pre-expanded, it flows into the void without generating the high expansion pressures associated with lifting foam — filling cavities, conforming to irregular shapes, and stabilizing the ground without disturbing or lifting the slab above.
Step 4 — Cure & Patch FILLFOAM™ cures quickly. Once the material has set, the injection holes are patched with new cement. In most cases, the area is ready for normal use the same day.
Step 5 — Follow-Up if Needed Depending on the size and scope of the void, our team may recommend a follow-up inspection to verify coverage and ensure no secondary voids remain in adjacent areas.
FILLFOAM™ VS. TRADITIONAL VOID FILLING METHODS
When it comes to filling underground voids, contractors have historically reached for flowable fill (a cement-based grout), dirt backfill, or stone. Here's why FILLFOAM™ wins on almost every comparison:
FILLFOAM™
Flowable Fill / Grout
Dirt Backfill
Requires heavy trucks/equipment?
No
Yes — requires batching plants and truck delivery
Yes — excavation often required
Cure time
Fast
Long
N/A — but settles over time
Weight added to soil
Extremely lightweight
Heavy
Moderate to heavy
Water resistance
Waterproof and permanent
Can erode or wash out
Erodes readily
Disruption to property
Minimal
Significant
Significant
Ideal for tight/irregular spaces?
Yes — flows into cavities
Limited
No
For most residential and commercial void filling situations in Western Washington, FILLFOAM™ is simply the smarter, faster, and less disruptive solution.
WHERE WE USE FILLFOAM™
FILLFOAM™ is a versatile solution that 1-866-SLABJACK deploys across a wide range of situations:
- Beneath residential concrete slabs — driveways, patios, pool decks, garage floors, and walkways where soil loss has compromised support
- Foundation support areas — stabilizing soil beneath foundations where voids are contributing to settling or movement
- Beneath porches and entry areas — one of the most common void locations in the Pacific Northwest, especially on older homes
- Commercial and municipal applications — parking lots, warehouse floors, loading areas, sidewalks, and other high-load surfaces where voids present safety and liability risks
- Post-tree-removal stabilization — filling root channels and residual voids after stump grinding or root removal
- Utility line void remediation — stabilizing soil after sewer, water, or drain line repair where surrounding soil has been compromised
- Beneath basement floors — protecting finished and unfinished basement slabs from further settlement or cracking
THE 1-866-SLABJACK DIFFERENCE: LOCAL EXPERTS, WESTERN WASHINGTON ROOTS
Anyone can pour foam. What sets 1-866-SLABJACK apart is 20+ years of hands-on experience with the specific soil conditions, drainage challenges, and climate realities of the Puget Sound region and all of Western Washington. We know what Pacific Northwest ground does to concrete — because we've seen it thousands of times, from Bellingham to Puyallup, from Bremerton to Issaquah.
Our crew has performed over 62 million pounds of concrete work across the Greater Seattle area and beyond. We've earned the trust of homeowners, property managers, commercial clients, and municipal crews across Snohomish, King, Pierce, Kitsap, Skagit, and Whatcom Counties. When you call 1-866-SLABJACK, you get:
- Certified, experienced technicians who treat your property with care
- Honest assessments — we'll tell you exactly what's needed and what's not
- Transparent pricing with no surprise add-ons
- A crew that shows up on time, does the job right, and cleans up when they leave
- A local company that lives and works in the same communities you do
SERVICE AREAS FOR FILLFOAM™ VOID FILLING
Based out of Lynnwood, WA, our crews serve the full Greater Seattle metro area and throughout Western Washington, including:
Seattle
Bellevue
Kirkland
Redmond
Sammamish
Issaquah
Bothell
Kenmore
Lynnwood
Everett
Marysville
Snohomish
Mukilteo
Edmonds
Shoreline
Renton
Kent
Auburn
Federal Way
Puyallup
Tacoma
Gig Harbor
Bremerton
Silverdale
Bainbridge Island
Mercer Island
Woodinville
Monroe
Duvall
Bellingham
Burlington
Oak Harbor
Stanwood
Coupeville
Poulsbo
Shelton
Olympia
And more throughout Snohomish, King, Pierce, Kitsap, Skagit, and Whatcom Counties
Don't let what's underground undermine everything above it.
If you're noticing the signs of subsurface voids — hollow-sounding concrete, new cracks, sinking slabs, or unexplained settling — it's time to call in the team that knows Western Washington ground better than anyone.
Schedule a FREE onsite inspection with 1-866-SLABJACK today. We'll assess the situation, explain your options clearly, and give you a straightforward proposal — no pressure, no runaround.
Call us: 1-866-SLABJACK (1-866-752-2522) Local: 425-747-1157 Or click below to schedule your free inspection online.
