BCAB 1963 - Protection for suspended garage floors over basements in townhouses

Protection for suspended garage floors over basements in townhouses

Project Description

The project is the alteration of an existing three-unit townhouse building constructed under Part 9.  Each of the units originally contained a built-in garage with a slab on grade floor.  As part of the alteration, the garage slabs were removed and further excavation and construction completed.  New suspended garage floors were constructed of reinforced concrete on metal decking, thereby creating room-sized spaces below the garages and extending the floor areas of lower levels.

As the project continues, a next step is to provide some means to address the water that may enter the garages, possibly in the form of snow brought into the garages by vehicles.

Applicable Code requirements (BCBC 2012¹)

Sentence 1.3.1.2.(1), Division B, Applicable Editions

(1) Where documents are referenced in this Code, they shall be the editions designated in Table 1.3.1.2.
CSA S413-07, Parking Structures (excerpt from Table 1.3.1.2.)

Sentence 9.3.1.1.(3), Division B, General

(3) Except as provided in Sentence (4), reinforced concrete shall be designed to conform to the requirements of Part 4.

Sentence 9.4.1.1.(1)(c)(ii), Division B, General

(4) Subject to the application limitations defined elsewhere in this Part, structural members and their connections shall
     (c) be designed according to Part 4 using the loads and deflection and vibration limits specified in
          (i) Part 9, or
          (ii) Part 4.

Sentence 4.4.2.1.(1), Division B, Design Basis for Parking Structures

(1) Parking structures shall be designed in conformance with CSA S413, “Parking Structures.”

Decision being appealed (Local Authority’s position)

Reinforced concrete must be designed in compliance with Part 4.  Each suspended slab is a parking structure and CSA S413-07 applies.

The garage slabs are not roofs but protection against water ingress – including water from melting snow brought in by vehicles – is necessary.  A membrane and drainage are required, including a means to protect the membrane from damage due to vehicle use.

Appellant's position

The garage slabs over living space are not parking structures.

Water protection must be applied to the top of the concrete to protect from water ingress and this should be considered under Part 5.  There is no clear requirement for a membrane on the garage slabs under Part 9 or Part 4 for garages over living space in a residential building.

Appeal Board Decision #1963

The Board confirms the decision of the local authority.

It is the determination of the Board that the townhouse garages are parking structures and the requirements of CSA S413-07 apply.

Reason for decision

Some aspects of the townhouse garage structures consist of reinforced concrete and the floors are subject to vehicular traffic.  Protection of the structure from corrosion is a requirement of Part 4 and the referenced standard includes various alternatives for systems to protect against water leakage and corrosion.

Don Pedde
Chair, Building Code Appeal Board

Dated:  May 29, 2025

¹ The local authority and the appellant agree that, due to the application date of the permits involved and the ongoing nature of the work, the BC Building Code 2012 applies.