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Demolition and Excavation

Launch Slideshow

Replacing a Slab Foundation

New perimeter footing and slab prep

Replacing a Slab Foundation

New perimeter footing and slab prep

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    A new steel-reinforced footing, anchored to holes drilled in the existing perimeter wall supports a block foundation wall between the laundry room and garage.

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    The new block foundation wall

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    An access opening between the new crawlspace and the existing basement was cut with a concrete saw equipped with a diamond blade. Note the sump cover.

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    The existing hearth extension gained additional support from a pair of short block walls and the short steel column visible at far right of photo.

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    The column's upper end was tightened against the cantilevered section of slab; a few squirts of polyurethane foam prevent squeaks between the slab and the OSB floor sheathing.

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    After the new laundry and family-room floor was framed and sheathed, the garage area was backfilled with compacted gravel in preparation for the new slab.

Dealing with the garage slab was a straightforward matter of breaking it into manageable chunks with demolition hammers and hauling away the rubble (see slideshow). But removing the laundry-room and family-room slab was complicated by the fact that its edges extended over the top of the side and rear foundation walls. Both the exterior wall framing and the fireplace brickwork at the end of the family room sat on top of the slab, and removing that portion of it would add a lot of work and expense.     

Instead, the mason’s crew cut the slab as close to the inside face of the exterior walls as possible. After making an initial cut with a gas-power concrete saw, they trimmed it back closer to the wall with an electric concrete saw. This left a suitable ledge for the sill plates that would later support the family-room floor joists.

We wanted to save the fireplace hearth extension, which was in pretty good shape. I suggested supporting the hearth with temporary supports before the slab was removed. But the mason thought that the weight of the fireplace bearing on the outer edge of the slab would be enough to hold it in place while we worked around it, and was willing to rebuild the fireplace if events proved him wrong. He was right.

Once both slabs were hauled away, the crew excavated the soil below the floor slabs with the aid of a skid steer and a small backhoe. We then poured a steel-reinforced footing and built a block wall at the rear of the garage to provide support for the new floor joists and to separate the crawlspace from the fill below the garage floor slab.