Small Garage Foundation Repair

A teardown would have prompted the relocation of the new garage some 9 feet further into an already-small yard to accommodate the town’s side-setback requirement of 12 feet.

When the author’s crew demoed the garage’s existing 2-inch-thick slab, they discovered that the walls were bearing on cinder blocks placed on their side, with the existing slab keyed into the voids.

Even with this thickened edge, the sill plates were 90% gone, due to their proximity to grade.

The bracing strategy was designed to support one wall at a time. To avoid damage to the existing shell, squaring up and leveling was kept to a minimum.

New 14-inch-deep footing forms were set at the same height as the existing slab and tied back to the diagonal bracing.

Over a couple of hours, the crew wheelbarrowed the concrete around the bracing to the forms ...

... then trowelled the scratch-coat finish.

They retrimmed the existing studs to allow for two block courses and a 2-by PT mudsill, then installed the block, filling the cores.

Tolerances were close — in a few places the mudsill had to be sledge-hammered into place.

A pair of Simpson A23Z clip angles on each stud connected the wall to the mudsill, which was connected to the block with wedge anchors placed 2 feet on center.

With the gable-end walls done, the existing rear wall could be readied for formwork.

Similar to the gable-end footings, two continuous #5 rebars were placed at the bottom of the footing. The rear footing was pinned to the gable ends with two #5 rebar pins drilled and epoxied into place.

Like the rear footing, the front wall footing returns were pinned to the new gable-end footings with two #5 rebars.

The blocks were toothed together at the corner.

The wider overhead door required the installation of a double 11 7/8-inch-deep Microllam header under the existing 4x4 top plate. A screw jack was used to level the opening and to support the beam until jack and king studs could be installed.

After laying down a layer of 4-inch gravel, reinforced 6-mil poly sheeting, and welded-wire mesh, the crew ran asphalt-impregnated fiberboard around the inside face of the footing.

Then they poured the new 4-inch slab flush with the top of the footing. The fiberboard serves to isolate the slab from the footing should any frost issues arise.

The apron slab was reinforced with wire mesh and sloped down toward the driveway 1 inch over its 4-foot width.

The bulk of the exterior finishes are on the front wall; new siding flanks a car-and-half-wide garage door.

The exposed block stem wall was parged with mortar, and the driveway was regraded with new gravel. Gutters were added, and a berm was created to help direct runoff away from the entry apron.

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