50 & 70 BAIF BOULEVARD
PARKING GARAGE REMEDIATION
OVERVIEW
​
FORSMITH Building Science Consultants (FORSMITH) was retained to conduct an assessment of a two-storey underground parking garage structure shared between two residential buildings located at 50 and 70 Baif Boulevard, Richmond Hill. The garage roof slab consisted of a conventionally reinforced concrete slab that was protected by a hot rubberized asphalt waterproofing membrane. The existing overburden above the parking structure included a combination of softscape and hardscape areas. The two suspended slabs were designed and constructed with expansion joints to allow for movement (expansion and contraction). Since its construction in the 1970’s, the parking garage had undergone many phases of repair and restoration. To assess the condition of the structure, FORSMITH completed a visual review to check and quantify concrete deterioration (cracking, spalling and/or delamination) at soffits, the suspended slabs, foundation walls and columns. In addition, destructive and non-destructive testing methods such as percussion hammer sounding, ground penetrating radar (GPR), half cell potential testing, and test cuts into the existing waterproofing membrane were used to further verify our observations. All the gathered information was presented in a formal assessment report that summarized the condition of every major structural and building envelope related component of the garage. Each component was categorized in terms of priority level for remedial action required. Based on this, FORSMITH offered recommendations for further investigation and a multi-year phased repair plan that would rehabilitate and prolong the service life of the structure.
​
PROBLEM
Based on the assessment, the deterioration on the garage roof slab, particularly along existing expansion joints, was the most critical component of the structure that needed to be addressed as soon as possible. The majority of deterioration observed on the roof slab soffit along the joints was in the form of significant concrete deterioration due to prolonged exposure to water and chloride ingress, which ultimately led to corrosion of the embedded steel reinforcement. The concrete deterioration identified at the ledge beam portion of the roof slab along expansion joints was of particular structural concern in several areas. As the beams’ intended purpose is to support the resting portion of the slab, major deterioration can significantly reduce their structural capacity.
​
CHALLENGE
Determining the best remedial course of action given the owner’s capital expenditure budget was one of the major challenges on this project. Since deterioration and its severity varied largely across the structure, and repairs to all components was not practical or financially feasible at one time, we recommended phased repairs, starting with most critical areas of deterioration in the near term. The first phase of repairs included remediation to the existing expansion joints in the roof slab, which required extensive concrete repairs, replacement/ supplementation of corroded steel reinforcement, and localized replacement of the existing waterproofing membrane. This was of the highest priority level due to the structural concern mentioned earlier, and the active leaks observed on the interior which were indicative of failure in the waterproofing. Access was another difficulty, as excavation and removal of the existing overburden on the roof slab, which consisted of both softscape and hardscape areas, including drive aisles, visitor’s parking spaces, pedestrian walkways, garden areas, flower beds and trees, was necessary to complete the repairs. The final major challenge was planning and coordinating the remedial work in a manner that mitigated the disturbance to the condominium’s daily operations and its residents while addressing the identified deficiencies to the structure and building envelope.
SOLUTION
​
Our recommendations for repair focused on the most critical areas exhibiting significant deterioration, in an effort to address these issues in the short term in order to mitigate further deterioration and prolong the overall service life of the structure. In turn, an estimated construction budget was presented to the owner based on historical data for the cost of similar work, adjusted for factors such as inflation, location, risk, size, time, quality, etc. Once retained, FORSMITH prepared a parking garage remediation design package including detailed specifications and drawings. By way of a competitive bidding process (ie. via tender), a general contractor was retained to complete the specified repairs. FORSMITH in turn applied for a building permit and provided engineering services including periodic technical field reviews, contract administration and project management during the entirety of the project duration. Working alongside the general contractor, FORSMITH was able to deliver the project on budget and on schedule, to the satisfaction of the client.
​
​
