John Corrent of Windsor, Ontario, had a problem. His 10-year-old, 30X40 foot driveway had sunk in several places. Two sections had dropped three inches, and a third had raised and lowered corners producing a teeter-totter effect. The driveway was becoming an unsightly safety hazard.

Corrent cringed at the thought of having to pay contractor estimates of up to $12,000. Before doing so, he called Robert Soulliere, owner of Soulliere Solutions Inc. Soulliere's company specializes in all sorts of tricky home repairs, including slabjacking -- the trade name for raising sunken concrete.

"After an afternoon's work, Robert handed me a bill for $642," says Corrent. "His only stipulation was not to drive on the cement for 48 hours. I was happy to oblige. Except for the cement patches covering the small holes that had to be drilled, you'd never know that my driveway had been touched."

Slabjacking is a growing business across Canada. For instance, Soulliere's 12-year-old company has sold franchises across Southern Ontario for prices ranging from $45,000 to $85,000. Homeowners with sunken driveways, steps, sidewalks, porches, and garage pads are taking advantage of this affordable and practical solution to save time and money.

What is Slabjacking
"The type of slab we raise is called 'floating concrete'," says Soulliere, who keeps his full-time workforce of eight men busy year round. The name, slabjacking, (also referred to as mudjacking or pressure grouting) is the process of jacking or raising up a slab of cement and restoring it to its original level. It can involve lifting one solid piece such as cement steps, or readjusting several pads. Regardless of thickness, number of cracks, or how much it has sunk, all manner of cement can be restored to its former grade.

Why Does Cement Sink and Crack?
"Cement moves in conjunction with the ground underneath it," says Soulliere. "Over time, the earth can erode due to moisture in the ground, poor initial fill compaction, poor drainage, or the ground's natural settling."

As the soil disperses or compacts, hollow areas and pressure points develop. Eventually, a combination of traffic and the concrete's own weight causes it to shift and/or crack, allowing water to enter and further wash the soil away.

How Does Slabjacking Work
"Slabjacking involves pumping slurry beneath the concrete through small holes drilled in the cement," says Soulliere. "It seeps into voids and crevices, depressing and stabilizing the existing subsoil, while raising the cement."

While all companies use this format, the actual mix, holes drilled and pouring methodology vary. Soulliere offers the following points to educate homeowners:

Slurry Mix
The mixture used can differ widely in content.
These include:
-A combination of sand and clay.
-Leftover aggregate recovery from cement trucks, commonly called snot.
-A by-product from coalmines called flyash.
-A combination of sand and silt called chirt.
-Polyurethane.
-A 98 per cent organic-free combination of sand, Portland cement and silty loam (the mix that Soulliere uses).

Once the job has been assessed, small holes approximately 1 1/4-inches in diameter are drilled at predetermined locations. A portable pump forces the slurry through the holes to raise and level the cement. However, Soulliere states that this step separates a job done right from a poor one.

"The size of the holes is important," says Soulliere. "I've seen large holes, drilled in order to pump the mixture underneath the concrete quicker, just to save time. This doesn't work. The slurry must be evenly distributed, which can only be done through strategically placed holes. After patching, big holes are more noticeable due to the difference in new and old cement colouring."

Soulliere also says that the slurry's thickness is of utmost importance. If it's too thin, it will run out from underneath the cement. Too thick, and it will form 'pillars or mushrooms'. These are pools of slurry that merge in spots instead of being distributed evenly. The best slurry mix has the consistency of porridge.

What are the Benefits?
Time and cost savings are the obvious benefits to slabjacking. Typically, a homeowner will pay between one- third and one-half the cost of new cement. Pouring new cement costs between $4 and $6 per square foot. Slabjacking runs $1.50 to $3. The cement is usually leveled in a matter of hours and can be used the same day.

In addition, slabjacking eliminates extra expenses such as re-seeding grass or repairing landscaping. Because a portable slabjacking pump is less than 28-inches-wide, it can be wheeled where necessary without damaging the surrounding ground.

Soulliere has one last piece of advice for homeowners. "When you receive your quote, make sure the cement to be raised is clearly marked out. I've seen company reps write their quote on the back of a business card. The homeowner has no idea of what work will be done, or how it will be completed. A detailed quote will help guarantee the homeowner will be walking on level ground for years to come."
-Photos courtesy of Soulliere Solutions, March/April 2004