By Emily Myers in Bricks & Bucks For Habitat Magazine
What began as a routine look at deterioration in a parking structure quickly turned into a much bigger project for the board of a 200-unit condo in Rego Park. With engineers on site to address mandated facade repairs, the condo board decided to deal with garage repairs — only to uncover failed waterproofing, cracked and flaking concrete and an unexpected electrical hazard.
Built in the 1980s, the condo has an underground single-level concrete garage where the roof is an outdoor asphalt parking lot. “You would think the majority of damage would be overhead,” says Michel Monteiro, senior project engineer at Cowley Engineering, the firm engaged by the board. Most of the damage, however, was on the slab on grade, the concrete poured directly onto the ground.
The structure’s original waterproof coatings had failed, allowing salt and de-icing chemicals to enter cracks and accelerate the deterioration. A large portion of slab needed to be repoured. “What started originally as minor cracks expanded, causing significant spalling and corrosion to the reinforcement,” Monteiro says. Spalling, the flaking or breaking away of concrete, is often associated with corrosion of steel reinforcements inside the structure.
Facing a cost of $1.6 million, the condo board is paying for the work with a loan and an assessment. In addition to financing, there was also the logistical challenge of moving cars offsite during the repairs. With close to 130 cars to work around, the project was completed in phases. To help accommodate vehicle owners, the property manager sought out public parking for 50 or 60 cars while each phase was completed.
Originally the concrete work was going to be partial depth repairs, but during the excavation the contractor uncovered an unexpected problem — live electrical conduits buried in the concrete. “Typically these conduits are buried within the soil beneath the slab,” Monteiro says. In this case, the live electrical wiring was two inches below the surface. Work was immediately halted in order to carry out a ground penetration radar (GPR) scan, a type of concrete X-ray to rule out other hidden dangers.
The discovery of buried electrical wires delayed the project by about three months as wiring was refitted overhead. The GPR scan did not identify live conduits in other parts of the garage, which meant the second and third phases of the project were unaffected. In addition to the new concrete on the garage floor, repairs have also been made to the perimeter of the building where water was getting into the garage from above.