Foundation, Crawlspace & Concrete Contractors in Mercer Island, WA
Terrafirma in Mercer Island, WA
At TerraFirma, we’re dedicated to protecting and enhancing the structural integrity of homes right here in Mercer Island and throughout Washington. For years, we’ve been helping local homeowners tackle the unique climate and soil challenges of our beautiful region.
From a cracking foundation to a musty basement, a damp crawl space, or an uneven concrete slab, TerraFirma has the expertise, tools, and reliable solutions to restore your home in Mercer Island and ensure it remains safe for years to come.
Mercer Island’s TOP-RATED Foundation & Basement Contractors
Contact us at (866) 486-7196 or use the form to the right.
Hours: Monday – Friday, 8am-5pm
Foundation Repair Mercer Island
Foundation issues can lead to significant damage to your home if they aren’t dealt with promptly. In Mercer Island, WA, homeowners may observe symptoms like cracks in the floors, bowing walls, and sagging floors, indicating potential structural problems beneath the surface. You might also notice doors that stick, windows that won’t close properly, or gaps appearing between the walls and ceilings. These signs could suggest that your foundation is shifting due to soil movement, water damage, or wear and tear over time.
At TerraFirma, we specialize in foundation repair on Mercer Island, offering tailored solutions that address the specific issues affecting your home’s foundation. Our process starts with a thorough inspection to identify the extent and root cause of the problem. From there, we recommend one or more of our trusted foundation repair systems:
Foundation piers
Our push and helical piers are expertly designed to stabilize and lift your foundation by transferring its weight to deeper, more stable soil. Helical piers are perfect for areas with known soil conditions, while push piers are ideal for locations with uncertain ground stability. Both solutions are minimally invasive and provide lasting results, making them great options for Mercer Island homeowners.
Wall Stabilization Systems
For cracked, bowing, or leaning walls, we offer a suite of reinforcement products. These include:
- CarbonArmor®: Made from fiber-reinforced polymers ten times stronger than steel.
- PowerBrace®: Zinc-plated steel beams that can be tightened over time.
- GeoLock® Anchors and Helical Tiebacks: These systems halt inward movement and gradually straighten walls over time.
- EverBrace™: Designed for severely deteriorated walls, this system replaces and reinforces failing foundation walls with steel supports.
We also offer grouted micropile tiebacks for difficult soil conditions, SmartJack® crawl space support posts for sagging floors, and vapor barriers to manage humidity and prevent further moisture damage.
Every solution comes with expert installation, convenient maintenance options, and transferable warranties, ensuring you have confidence and peace of mind in your Mercer Island home.
Basement Waterproofing Mercer Island
Don’t let a wet basement ruin your home on Mercer Island. Moisture can lead to mold, mildew, structural damage, and even affect your indoor air quality. Look out for signs of water intrusion like musty odors, stained walls, pooling water, or white, powdery efflorescence that appears when water evaporates. Remember, even a small crack in your basement wall can turn into a big entry point for moisture!
TerraFirma provides expert basement waterproofing solutions in Mercer Island, ensuring your space stays dry, healthy, and functional—whatever the weather brings.
Crawl Space Repair Mercer Island
Crawl spaces might be out of sight, but they play a vital role in your home’s structure and air quality here in Mercer Island. If not properly maintained, a neglected crawl space can become a breeding ground for mold, pests, and standing water. These issues can lead to wood rot, unpleasant odors, and even respiratory problems for those living in your home.
We understand the unique crawl space challenges in Mercer Island, WA. That’s why TerraFirma offers tailored crawl space repair services to tackle moisture, mold, pests, and sagging floors with comprehensive encapsulation, effective drainage solutions, and sturdy structural support.

Encapsulation & Drainage
We begin by sealing the crawl space with our VaporLoc Elite liner, a 120-mil thick waterproof barrier that blocks moisture, soil gases, and allergens. To ensure proper drainage:
- We use drainage matting under the liner to guide water to your perimeter drain or sump pump.
- Sump pumps remove water quickly and efficiently, even during heavy rain or high water table conditions.

Crawl Space Entry & Vent Solutions
- EverLast™ Doors & Access Wells: Waterproof, durable entry systems that keep out pests and moisture.
- Turtl™ Access Well: An attractive, lockable access solution in several colors.
- Vent Covers: Sealing crawl space vents prevent outdoor air, moisture, and insects from entering.
Crawlspace repair in Mercer Island is crucial to maintaining your home’s overall health and energy efficiency.

Structural Repairs
To support sagging or weak floor joists, our SmartJack® Support Posts offer adjustable, galvanized steel columns that restore floor stability. These are fast to install and offer permanent results.

Dehumidifiers & Monitoring
Install a SaniDry Sedona dehumidifier to maintain healthy humidity levels year-round. For added security, our ShipShape™ System offers 24/7 performance monitoring, proactive maintenance alerts, and remote control of your crawl space systems.

Concrete Repair Mercer Island
Cracked, uneven, or damaged concrete isn’t just an eyesore—it can pose a safety risk. Issues like poor soil compaction, freeze-thaw cycles, erosion, and tree root growth can cause these problems to arise. That’s why homeowners in Mercer Island trust us to repair their sidewalks, patios, driveways, and concrete slabs quickly and effectively.
TerraFirma provides quick, clean, and durable concrete leveling and repair services for Mercer Island, using cutting-edge polyurethane foam injection and expert crack sealing.
PolyLevel® Concrete Lifting
PolyLevel uses expanding polyurethane foam to lift and stabilize concrete slabs. This non-invasive method is perfect for residents of Mercer Island, WA:
- Sidewalks – Eliminates tripping hazards and restores smooth walkways.
- Driveways – Prevents further cracking and improves curb appeal.
- Patios, Porches, and Pool Decks – Ensures proper drainage and surface stability.
NexusPro™ Crack & Joint Sealant
To prevent water intrusion that can lead to further sinking, we apply NexusPro, a UV-resistant silicone-based joint sealant that:
- Cures in just 60 minutes.
- Withstands extreme weather and heavy use.
- Includes color-matched sand for a clean, polished look.
SealantPro™ Concrete Protection
After sealing and lifting your concrete, SealantPro provides a long-term barrier against moisture, chemicals, and seasonal temperature changes. It penetrates deep into concrete to resist stains, flaking, and surface erosion.
We also provide commercial concrete repair in Mercer Island, WA for industrial buildings, warehouse floors, roads, runways, and rail lines—using the same high-quality systems we trust for residential properties.
Earthquake Retrofitting Mercer Island, WA
Much of the Pacific Northwest, including Mercer Island, is located in an active seismic zone. Homes constructed before the updated building codes of the 1990s are particularly at risk. Even a minor earthquake can lead to homes shifting off their foundations or suffering significant structural damage.
TerraFirma’s earthquake retrofitting services help secure your Mercer Island home to its foundation and strengthen its ability to withstand seismic events.
Retrofitting your home for earthquakes in Mercer Island not only helps you stay safer but can also lead to lower insurance premiums, reduced deductibles, and access to coverage options that may not have been available before.
How We Retrofit
Assessment & Planning
Retrofitting your home in Mercer Island starts with a thorough assessment of its current condition. Our experienced professionals, including structural engineers and certified technicians, will carefully inspect your property to pinpoint any weaknesses and suggest the best solutions for improvement.
Our evaluation involves a thorough inspection of the foundation, walls, roof, and overall structure. Following this, our engineer creates a detailed retrofitting plan tailored to the findings.
Foundation Bolting
Securing the foundation is an important next step here on Mercer Island. Our skilled technicians install anchor bolts to firmly attach your house to its foundation, ensuring stability and preventing any lateral movement during an earthquake.
Our process involves drilling into the foundation and installing steel bolts. Our team tightens these bolts to reinforce the structure, boosting its stability and making it more resilient against seismic activity.
Adding Shear Walls
Shear walls play a vital role in earthquake retrofitting on Mercer Island, helping to distribute seismic forces and keep buildings standing strong during tremors.
“Shear walls are usually made from plywood or other durable materials and are strategically placed throughout homes, especially in cripple walls. These walls enhance support and stability, helping to minimize the risk of damage during an earthquake, a crucial consideration for residences in Mercer Island.”
Bracing & Reinforcing
Next, we’ll enhance and strengthen key areas of your home with steel braces and straps. Our team will install these to essential structural components like the roof, walls, and floors. This step boosts your home’s overall stability, providing a robust framework designed to withstand seismic forces right here in Mercer Island.
Securing Applicances
Securing your appliances helps create a safer home for everyone on Mercer Island. Anchoring items like water heaters and refrigerators is crucial. Our technicians also ensure that gas meters are properly protected to minimize the risk of gas leaks.
Reparing Foundations
During retrofitting, technicians may notice substantial foundation damage that needs immediate repair. Adding crawl space support posts and foundation piers, and stabilizing the walls are some of the ways TerraFirma can reinforce your foundation.

Secure Your Mercer Island Home Today
At TerraFirma, we’ve spent over 25 years helping homeowners in Mercer Island and across the Pacific Northwest protect their homes from the ground up. From foundation repair and basement waterproofing to crawl space encapsulation, concrete leveling, and earthquake retrofitting, our team delivers top-tier craftsmanship with trusted products, proven systems, and lasting warranties.
Every home in Mercer Island, WA is unique, and at TerraFirma, we have the solutions to tackle every challenge. Reach out to us today for a free in-home estimate and find out how we can help enhance the safety, health, and value of your home for years to come.
Mercer Island
Homeowners Frequently Asked Questions
How does rain put my home at risk ?
SeaTac soils are impacted by heavy rains causing hydrostatic pressure. This leads to cracks in foundations and basements and may cause your foundation to settle or sink. Engineered support structures and comprehensive drainage systems are key to keeping your home dry, safe, and stable.
What’s the best way to repair concrete?
The NexusPro solution is a commercial grade joint sealant that offers several advantages over traditional concrete crack repairs. Its fast cure time (60 minutes) and performance under extreme temperatures makes it a perfect match for concrete repairs.
What types of cracks in my foundation or basement should I be concerned with?
Houses are susceptible to cracks in basements due to heavy rains and wet soils. Watch out for horizontal or stair step cracking along the foundation wall, diagonal cracks in the corners, crumbling walls and inward bulges.
How to fix a leaking basement floor?
If you have water coming through the floor or windows to your basement, the first step is installing a perimeter drain system. We can also install a direct drainage channel, which will help direct any water that comes through the crack into the drain and your sump pump.
Are you noticing damp drywall and carpet in your basement?
Musty smells, walls that feel damp to the touch, and ground-level leaks are all indicators that your basement may need to be waterproofed. Don’t wait until the next heavy rain to protect your home from water damage.
Which vapor barrier is best for weeping walls?
The VaporLoc Elite Wall System is better for weeping walls than other commonly used vapor barriers. The VLE system has double sealed seams, waterproof material (not water-resistant), and is much thicker than vapor barriers available at retail stores.
Can I turn my crawl space into storage?
TerraFirma offers comprehensive encapsulation solutions to keep your crawl space clean, dry, and secure from outside threats. Our industry-leading vapor barrier system keeps out destructive moisture while greatly improving your indoor air quality. In most homes, TerraFirma can even encapsulate your crawl space, giving you a clean, dry area suitable for storage.
How to repair damaged concrete?
While you could seal concrete with urethane caulk found at your local big-box DIY store, that is a solution that is prone to cracking, bubbling and drying out over time. The local experts at TerraFirma are here to help with long lasting solutions to level seal your unprotected joints and cracked concrete.
What is that bad smell coming up from my drain?
Unwanted air and gasses are coming up through your home’s drain system. A great fix is our TrenchLock™ drain insert that can be installed in an existing trench drain to allow water down without allowing air to come up. The system comes with balls that fit over the drainage holes, which create an airtight seal when there is no water.
What is the difference between helical piers and push piers?
Helical piers and push piers are both types of foundation repair methods, but they differ in their design and installation process. The choice between helical piers and push piers depends on factors such as soil conditions and structural requirements. Helical piers are often preferred in areas with weak or unstable soil conditions.
How long does basement waterproofing last?
TerraFirma-installed waterproofing systems are expected to last decades with regular care & maintenance. We also warranty our installations, our WaterGuard and DryTrak drainage systems come with a transferrable lifetime warranty. Terms apply, view the details here. We stand by our work and the quality of the systems we install.