Concrete Leveling and Lifting in Smithtown, NY

Concrete leveling raises a sunken slab back to grade by filling the void beneath it, and around Smithtown it matters because the ground under a walk or driveway can give out long before the concrete wears out. The Town's median house was built in 1968, and Census estimates put 30,209 of its 40,714 homes before 1980, so many walks, stoops and driveway panels have sat for decades on glacial sand or foundation backfill while roof water ran past them. Two methods do the lifting. Polyurethane foam goes in through holes 3/8 to 5/8 inch across and weighs 2 to 4 pounds per cubic foot. Mudjacking pumps a cement-and-soil slurry weighing over 100 pounds per cubic foot through holes 1 to 2 inches across. Below are the figures for both, the Town's sidewalk rules, national prices, and the cases where lifting is the wrong fix.

Published guides price slab lifting by the square foot, with a floor for small jobs. One national guide puts the average at $3 to $12 per square foot and $700 to $5,000 per job, with mudjacking at $4 to $9, foam at $8 to $25, and a minimum job fee of $300 to $700 or more at most contractors. A second national survey puts most leveling jobs at $661 to $1,874, says foam can cost up to four times as much as mudjacking, and puts labor at 70% to 80% of a foam job. Slab area, how far it has dropped, the method and access for the equipment set the price. For comparison, the first publisher's sidewalk guide puts removal and replacement at $10 to $25 or more per square foot, and the Smithtown concrete cost page sets leveling beside replacement.

The two concrete lifting methods differ in weight, hole size and wait. Polyurethane lifting, or polyjacking, injects a two-part foam that expands in the void and hardens. One maker of both foam rigs and mudjacking pumps puts the foam at 2 to 4 pounds per cubic foot, and manufacturer data sheets list free-rise compressive strengths of 50 and 80 psi. It is traffic-ready in about 15 minutes, and its hydrophobic grades are made to displace water. Mudjacking, the traditional form of slabjacking, pumps sand, soil, water and often portland cement through holes 1 to 2 inches across. That slurry weighs over 100 pounds per cubic foot and needs 24 to 48 hours to cure. The same maker cautions that the heavier fill can add to settling over unstable soil, and that soil-based slurry can wash out and let the slab drop again.

A slab on grade that is whole, or cracked into a few large pieces, can often be raised: driveway panels that dropped at the garage or apron, front walks, patios, stoops that tip toward the walk, garage floors and pool decks. One national guide prices foam by the job: $320 to $1,000 for 40 square feet of steps, $800 to $2,500 for a 100-square-foot sidewalk, $2,880 to $9,000 for a 360-square-foot garage floor and $3,200 to $10,000 for a 400-square-foot pool deck. Pool decks need one extra check. The flexible joint between the deck and the coping, the cap along the pool edge, must stay clear so a rising deck cannot shove the coping and its mortar bed, and a draft industry standard asks decks to drain away from the pool or to deck drains at a slope of at least 1/8 inch per foot. A garage or shed slab broken into many pieces calls for new slabs and footings instead.

Paperwork depends on who owns the slab. Your driveway, walk, stoop and patio are private work, though Head of the Harbor says no work may be carried out in that village without a permit from its Building Inspector. The public sidewalk is different: Town Code Section 245-4 defines it as the area between the curbline and the property line, and Section 245-15 requires a permit from the Superintendent of Highways for any excavation in a Town street or sidewalk, so a sunken public flag, one square of sidewalk, starts with the Town rather than a lifting crew. The Village of the Branch has its own street and sidewalk permit under Section 234-1. Cold slows cement grout: one state highway spec for grouting under pavement bars the work when the bottom of the slab is below 40 degrees F, and Islip averages 24.8 nights at or below 32 degrees F in January. The driveway apron and sidewalk page covers replacing a flag outright.

A lift lasts as long as the void stays closed. One national cost guide says professionally leveled concrete lasts 5 to 10 years or more; the equipment maker above claims 20 years or more for foam and 5 to 10 years for mudjacking, depending on soil and water exposure. Carry downspouts past the slab, raise it back to a fall away from the house (a ready-mix industry guide asks driveways to slope at least 1/8 inch per foot away from structures), and caulk the joints and edges afterward. If panel after panel keeps dropping, the base has failed, and a new concrete driveway on a compacted base is the lasting repair. For a price, measure the drop at each joint, photograph it with a level laid across, and send the photos through the quote form.