Open Web Steel Joists - Roof and Floor Loading Guidelines

The following information was offered to managers and operators of provincially owned buildings by the Department of Transportation and Public Works as an interim guideline to limit the effects of excessive snow and ice accumulation and excessive floor loads. It is recommended that these guidelines be used until a competent structural evaluation is completed. A qualified structural engineer (see note) may determine appropriate interim precautionary measures that would be more suitable, based on the condition of the structural members and the specified uniformly distributed live loads and design dead loads for the roof and floor assemblies based on the location and occupant load of the building.

These guidelines apply to all building roofs supported by "Robb" or suspected "Robb" joists erected between 1963 and 1985.

Guidelines for controlling snow accumulation on roofs

1.Building maintenance staff should visually inspect each roof to monitor snow and ice accumulation. Inspect roof immediately after major winter storms where precipitation more than 200 mm [8"] of snow fall and/or 50 mm [2"] of rain fall has occurred in a 24 hour period.

2.These interim guidelines are based on allowable wet snow loads of 50% of the design roof snow+rain load. Snow accumulation on roofs should not exceed 300 mm [12"] depth until satisfactory engineering inspection results are available.

3.Remove snow accumulations, where high and low roofs meet, and around roof top mechanical units.

4.It is recommended to take care in the removal of snow and/or ice accumulation to prevent damage to the roof membrane. Avoid removal within 50 mm [2"] of the surface of the roof membrane.

5. Inspect roof drains and ensure drains are working properly.

6.When removing snow from one section of a roof, avoid travelling over and compacting snow on adjacent roof sections.

7.These are interim measures to be taken until you have a structural evaluation completed. A qualified structural engineer may determine appropriate interim precautionary measures that would be more suitable, based on the condition of the structural members and the design snow and rain loads for the location of the building.

Guidelines for loading on Floors

1.Assembly areas, libraries and other areas with heavy loads on floors should be inspected. If you have floors which are supported by open web steel joists, consideration should be given to restrict occupancy to not exceed one [1] adult person per one square metre [11 sq. ft.]

2.This is an interim measure to be taken until you have a structural evaluation completed. A qualified structural engineer may determine appropriate interim precautionary measures that would be more suitable, based on the condition of the structural members and the design floor loads for the actual use of the building.

Note: The Department of Transportation and Public Works commissioned teams of: a registered professional structural and welding engineer accredited by the Canadian Welding Bureau according to CSA Standard W47.1 and with a minium of fifteen years experience, and welding inspectors accredited by the Canadian Welding Bureau according to CSA Standard W178.2-96., Level II or Level III, and who have been engaged predominantly as a welding inspector for the past 5 years.