Repairing a Sinking Home Foundation With Slab Jacking

A sinking home foundation is a common problem that can have serious consequences if left untreated. Slab jacking is an effective solution for lifting and leveling sunken concrete slabs to restore the integrity of the foundation.

What Causes Foundation Settling?

There are several potential causes of foundation settling:

Soil movement – Clay soils can shrink and swell with changing moisture levels, causing uneven settling. Drought conditions often lead to foundation issues. Tree roots can also disrupt soil under foundations.
Improper compaction – Insufficient compacting of backfill soil during construction can lead to settling over time.
Erosion – Water drainage issues can erode soil near the foundation, causing sinking and cracks.
Underlying voids – Underground voids from old tree roots or construction debris can collapse, creating points of weakness.
Heavy loads – Overloading the soil beneath the foundation with heavy equipment use or additions to the home can cause subsidence.

Signs of a Sinking Foundation

Some common signs that your foundation may be sinking include:

Cracks in walls or ceilings – Horizontal cracks are a major red flag for foundation problems. Vertical cracks can also indicate sinking foundations.
Floor unevenness – Floors that are no longer level often signal foundation settling. You may notice uneven floors when walking across rooms or rolling objects like marbles.
Doors or windows sticking – If doors and windows stick or rub due to shifting, the foundation could be settling unevenly.
Separating walls – Gaps forming between walls, ceilings, and floors indicate foundation instability.
Bowing walls – Walls that are no longer vertical can signal foundations sinking on one side.

Dangers of Sinking Foundations

It’s important to address sinking foundation issues promptly before further damage occurs. Potential risks include:

Declining home value – Severe foundation problems can make a home difficult or impossible to sell.
Structural damage – Continued sinking can cause walls to crack and bow, eventually leading to collapse.
Difficulty opening doors/windows – If sinking progresses, doors and windows can become sealed shut by shifts.
Plumbing leaks – Pipes can rupture as foundations shift, causing water damage.
Electrical issues – Breaks in buried power and gas lines under shifting foundations are fire and shock hazards.
Pest/moisture infiltration – Gaps from foundation issues allow pests and moisture intrusion, potentially causing rot.
Health concerns – Bowing walls, sagging floors, mold growth, and other issues can make a home unsafe.

How Slab Jacking Works

Slab jacking, also known as mud jacking or concrete lifting, is a process that raises and levels sunken concrete slabs by injecting a fill material underneath the slab to lift it back into place. Here is the general slab jacking procedure:

Holes are drilled into the slab at strategic places.
Lift cylinders with jack pumps are placed into the holes.
Polyurethane foam or a cement mixture is pumped beneath the slab through the holes.
As the area fills, the concrete slab is slowly lifted back to its original elevation.
Once lifted, the holes are patched and the slab is stable in its new level position.

Slab jacking is an efficient alternative to tearing out and replacing settled slabs. The materials injected can fill voids and increase support. The process takes only a few days and the cost is typically 1/3 that of replacement.

Benefits of Using Slab Jacking

Key benefits of slab jacking for repairing sinking home foundations include:

Less invasive – The slab remains largely undisturbed, avoiding major demolition.
Cost effective – Average savings of 60-70% over slab replacement.
Precise leveling – Laser leveling allows lift cylinders to elevate each portion of slab independently.
Doesn’t disturb landscaping – Yard plants, pavers, etc. aren’t affected like with slab replacement.
Improves soil stability – Foam or grout fills voids and consolidates the soil underneath.
Can lift heavy slabs – Commercial projects with thick slabs are possible.
Long lasting – Can provide permanent solution and prevent continued sinking.
Preserves slab integrity – Avoids breaking up and re-pouring concrete.
Minimal downtime – Homeowners typically only need to vacate for 1-3 days.

Materials Used in Slab Jacking

Two main types of fill are used to lift concrete slabs:

Polyurethane Foam

Expanding polyurethane foam is lightweight, able to fill voids, and adds stability. Two liquid components are mixed under the slab to expand rapidly into rigid foam with high compressive strength.

Pros: Lightweight, flows easily into voids, adds insulation value, fast curing

Cons: More expensive, can over-expand and lift slab too high

Cement Grout

A thin cement mixture similar to concrete but with smaller aggregate. Typically contains cement, fly ash, lime, sand and water.

Pros: Quickly sets for stability, non-compressive, won’t over-lift, cheaper than foam in most cases

Cons: Heavyweight, won’t fill voids, slower injection rate than foam

Soil tests help determine best material to lift the slab while providing lasting support. Grout works well for slabs that just need leveling, while foam is better for filling voids.

Factors That Influence Slab Jacking Costs

Several variables affect the overall costs of slab jacking:

Area being lifted – Total square footage and number of slabs. Large areas or multiple slabs add cost.
Slab thickness – Thicker commercial slabs require more material to lift.
Lift height – The more the slab needs to be elevated, the greater the cost.
Accessibility – Ease of accessing the underslab area impacts equipment needs.
Material used – Polyurethane foam typically costs more than concrete or grout.
Site conditions – Complicated projects due to soil type, drainage, etc. add cost.
Additional repairs – Any slab reinforcement, crack sealing, or drainage improvements add cost.

Typical residential slab jacking costs range from $3-$8 per square foot. Get quotes from multiple companies as rates can vary significantly.

Questions to Ask Slab Jacking Contractors

When selecting a slab jacking company, important questions to ask include:

Do you have experience with projects similar to mine? Ask for examples of past work.
Are you insured and licensed for this type of project? Ask to see current credentials.
What preparation work is done prior to lifting the slab? Soil testing, leak checks, etc.
What materials do you use for slab lifting and what are the benefits? Look for technical expertise.
Do you offer any warranties or guarantees on your slab jacking work? Quality providers often warranty their work.
Can you provide references from past clients I can contact? Reputable companies will oblige.
How long will the project take and what is the step-by-step process? A detailed plan signals competence.
What potential disruption or restrictions are there to my home during the work? Look for minimal inconvenience.
Do you have a licensed structural engineer on staff? Specialized expertise is ideal.

Signs It’s Time to Call a Pro for Slab Jacking

If you are experiencing sinking slabs, it’s important to have a professional evaluation. Warning signs it’s time to call for slab jacking include:

Cracks wider than 1/4 inch
Cracks that keep reopening
Floor sections becoming increasingly unlevel
Doors that stick and won’t close properly
Cinder block foundation cracks
Walls or ceilings developing bowing or sagging
Fixtures like lights and cabinets becoming misaligned
Plumbing leaks, moisture intrusion, or musty smells

If caught early, slab jacking can often stabilize slight settling and prevent further damage. It’s best to call for professional slab jacking at the first signs of foundation instability.

DIY Slab Jacking Risks

While do-it-yourself slab jacking may seem like an affordable option, it carries considerable risks:

Inconsistent lifting – It’s challenging to lift large slabs evenly without commercial equipment.
Major underfilling or overfilling – Precise control of fill levels is difficult, which can destabilize the slab when incorrect.
Inadequate soil testing – Underlying soil problems need identification to use the right fill material.
Lack of experience – Insufficient injection points or improper pump pressure can limit effectiveness.
No insured warranty – DIY has no consumer protections if problems occur.
Potential injury – Mishandling of heavy equipment can be dangerous.

Leave slab jacking to the professional crews equipped for safe, controlled lifting. The potential for costly failed repairs makes DIY a poor choice.

How to Choose a Quality Slab Jacking Contractor

Key tips for choosing a qualified slab jacking contractor:

Check reviews – Look for consistently positive customer feedback about quality of work.
Verify licensing – Make sure the company meets all state and local licensing requirements.
Look for CSL insurance – CSL coverage protects your property if damage occurs.
Choose experience – Ask how many slab jacking projects they complete annually.
Request project portfolio – Reputable firms will provide past project examples.
Check qualifications – Technicians should be thoroughly trained and certified.
Consider specialties – Some companies specialize in commercial or residential projects.
Get multiple bids – To determine fair pricing, get quotes from 3-5 slab jacking companies.

What to Expect During the Slab Jacking Process

If you choose to move forward with slab jacking, here is a typical timeline of what to expect:

Day 1 – Preparation – The team will evaluate the slab(s), identify needed access points, perform any soil testing, and layout the plan.
Day 2 – Lifting – Holes are drilled, pump cylinders inserted, and the slab is slowly lifted back to level position as material is injected.
Day 3 – Completion – After the slab is lifted and has time to cure in the new position, holes are patched and sealed. A final level check is done.
1 week post – Protection – Avoid heavy loads on the slab and give the fill material time to fully cure before removing all restrictions.

Throughout the process, the lifting team monitors progress and makes any needed adjustments to achieve optimal slab levelness. With quality work, your foundation should be restored to full stability.

Preventing Future Foundation Settling

While slab jacking is an effective solution for current foundation problems, you can take proactive steps to prevent sinking and settling from reoccurring:

Regularly inspect – Check for new cracks or separations that signal soil movement.
Maintain drainage – Ensure downspouts, gutters and grading keep moisture away from foundations.
Avoid over-loading slabs – Prevent heavy point loads from vehicles, equipment, furniture, etc.
Removal problem trees – Eliminate trees that could disrupt soil as roots spread.
Control soil moisture – Water soil evenly around perimeter during dry periods if needed.
Get sump pumps – Keep basements and crawlspaces dry to prevent erosion and maintain soil stability.
Consult landscaping pros – Seek advice on best plants and irrigation for foundation areas.
Address leaks quickly – Prevent water from intruding under slabs through plumbing, seals, etc.

With attentive property maintenance and care, you can help minimize foundation instability long-term. Seek help at the first sign of new slab settling.

Conclusion

Sinking concrete slabs are a common issue that occurs as underlying soil shifts over time. If left unaddressed, ongoing foundation settling can lead to serious structural damage. Slab jacking provides an effective repair solution that lifts and levels sunken slabs through the controlled injection of stabilizing material. The polyurethane foams and cement grouts used can fill voids and consolidate the soil beneath slabs to prevent continued sinking. Compared to full slab replacement, slab jacking is far less invasive, less expensive, and faster. With the help of professional slab jacking contractors, concrete slabs can be precisely lifted back into proper alignment to restore a home’s structural integrity. Careful maintenance and preventative care can help minimize the need for future foundation repairs using slab jacking.