Workmanship
This factor is determined on how the design is executed by the contractor from a workmanship perspective as well as the quality control measures implemented during construction. Deviation from a sound design or by ignoring standard waterproofing installation standards and procedures can also lead to premature failure. Misguided practices include, but are not limited to, improper concrete surface preparation, a high moisture content on the concrete slab surface, or not following application procedures from the manufacturer which include mixing of material, curing, application temperature, thicknesses, etc.
Throughout the author’s entire career, he has only seen two garage roof slabs to wall junctions with missing waterproofing. The absence of proper waterproofing on below grade walls and slabs is a huge risk and one of the major factors that contributed to the collapse of the Algo Centre Mall roof located at Elliot Lake in 2012 according to the forensic engineering report.
Assessment
Underground parking garage and basement condition assessments should be performed by licensed professional engineers with experience in identifying problems early on such as water penetration at walls, slabs, expansion joints, concrete deterioration, drainage issues, etc. A condition assessment report should include quantified observations, conclusions, and recommendations for repairs complete with budget estimates.
Unfortunately, many building owners request a condition assessment far too late after the waterproofing membrane breaches have caused significant deterioration to the concrete. The only way to stop this from reoccurring is to legislate mandatory structural condition assessments for underground parking garages in Ontario every three to five years as enacted by New York State and Quebec, respectively. Further, if any structural concerns and remedial repairs are communicated to the building owners, there should be an enforcement strategy to ensure the deficiencies outlined are addressed within a specified timeframe.
Recently, a 98-year-old detached house was undergoing basement renovations and the contractor discovered major sub floor damage which was caused by water penetration from the exterior concrete block foundation wall. The wall was observed to be protruding 50 to 75 mm (2 to 3 in.) out of plane likely from frost.
This is a very serious condition with potential for the foundation wall to catastrophically collapse. Emergency shoring has been installed and the wall was completely replaced with new waterproofing and drainage installed along the entire length of the wall elevation.
