Mallinckrodt Plaza Waterproofing

The Mallinckrodt Condominiums parking structure was constructed in 2005 as part of a project to convert the adjacent historic school to condominiums. It is a one level, below grade post-tension parking structure with an above grade plaza concealing the parking structure. The plaza has two surface parking lots, multiple planters, trees, and a water fountain.

Almost since construction was completed, structural slab cracking and water leaking had been an ongoing concern. Walker was retained by the condominium board to perform a condition assessment to determine if the structural slab was safe, the root cause of the water leakage, potential repair solutions, and an opinion of probable costs for the various repair options.

Walker’s condition assessment included visual reviews, nondestructive testing to identify the as-constructed slab reinforcement, structural analysis, and openings in the concrete topping slab and landscaping to review the existing buried waterproofing system condition.

Walker’s assessment determined the structural slab was safe.  However, Walker documented widespread water infiltration through cracking in the structural slab, failed buried waterproofing that easily peeled away from the structural slab surface, improper waterproofing design, and lack of drainage within the planters. The concern was that without repairs, the water infiltration could lead to corrosion and deterioration of the concrete structural slab. Walker recommended a program consisting of removal and replacement of the buried waterproofing membrane, which necessitated removal and replacement of all of the plaza landscaping and surface parking lots.

Following the condition assessment, the condominium board engaged Walker to prepare construction documents, assist with bidding, and for construction administration. Walker prepared construction documents for the complete demolition of the plaza level parking lots and landscaping to replace the existing the waterproofing with a higher quality membrane and additional surface drainage within the platers and lot perimeter. The new waterproofing membrane was tested for water leakage at the completion of every phase using non-destructive electric field vector mapping testing. The plaza wearing surface and elements were then cast and restored to their original positions.

Walker’s team coordinated with the condominium’s landscape architect to secure village appearance review approval of all new landscaping. The structural slab is now protected by a new layer of waterproofing membrane that will provide a long life for the structure.