Stepped Buttresses for a Row House Basement

Engineer Kathleen Dunne’s prescription for supporting a shared rubblestone foundation wall called for a stepped reinforced buttress, sloped at the bottom to leave existing bearing soil undisturbed, and braced at the toe by the new basement slab at the lowered floor level.

Workers excavate Brooklyn native soils by hand in the 100-year-old basement in preparation for forming and pouring center buttress sections. Corner buttresses are already in place.

Workers place and tie rebar for buttress sections in a Brooklyn basement as part of a project to lower the basement floor. The buttress will stabilize the basement wall, which is shared with an adjacent dwelling.

Workers assemble plywood forms in preparation for a concrete pour. The job was staged in order to maintain stability of the shared basement wall: end and center sections of the buttress were formed and placed first, then the center sections were excavated, formed, and poured.

Concrete for the new buttress structure had to be pumped in from the street. Here, the concrete truck and pump truck are parked in front of the house.

Workers place concrete in the forms for a reinforcing buttress structure in the Brooklyn row house basement.

Concrete flows into the stepped forms for a reinforcing buttress. The concrete will set in contact with the existing foundation structure and undisturbed site soils, maintaining the stability of a common party wall that supports the project house as well as a neighboring dwelling.

Concrete curing in the stepped forms for a reinforced buttress designed to stabilize a common basement foundation wall. Once the new buttress cures, remaining soil in the basement can be excavated and a new concrete slab will be placed to brace the toe of the buttress structure and provide a floor for the new, lowered basement living space.

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