BCAB #1041 - Glass in Skylights
December 15, 1988
Re: Glass in Skylights
With reference to your letter of October 28, 1988 regarding the type of glass required in skylights. The information submitted included tests of the aluminum skylight bars used in the system under review; we note that the tests were purely to determine the load bearing capacity of the bars, and that they assumed the glass used would be capable of carrying the required loads.
On a general basis the Code requires safety glass in locations where it could be subject to human impact, and also as a deterrent to unauthorized entry. Apart from these locations Clause 37 of Commentary K in Chapter 4 of the Supplement to the National Building Code refers to the use of safety glass under special circumstances. This requires a degree of judgement by the authority having jurisdiction, having regard to the particular circumstances of any installation.
In dealing with your situation, and also to provide general policy guidance, we have no basic disagreement with your proposal that single glazing be of safety glass and with double or multiple glazing the bottom light be of safety glass. In the case of a skylight, the use of safety glass is not mandatory under the provisions of the Code.
The correspondence also mentions glass set in a steeply sloping roof. In such a situation, again on a general basis, we are unable to accept that safety glass is required to prevent injury to people outside the building. While some condition may, at some time, justify such a need, the chief purpose is to protect people within the building, or beneath the roof; apart from this we could not differentiate between such glazing and normal windows.
As a matter of general information we would draw attention to the need for adequate edge bearing to support glass. Thermal or other movement must be accepted as inevitable, and no design should permit a situation where clearances allow a sheet to move laterally in one direction to an extent that it is no longer supported by the bearing on the opposite side.
J.C. Currie, Chair