Safety Codes Bulletin: Installation of Deck and Roof Pad Footings

Purpose

To ensure columns are supported on properly designed and installed footings by using forms around all pad footings.

Discussion

Footings depth needs to be a minimum of 100mm or the width of the projection from the edge of the column (supported element). If the footing is not installed in a form, it is impossible to determine the required depth of the footing. If the “blob” is 36 inches wide and the column is 12 inches, this would require a footing 12 inches deep since the edges taper over the area, we cannot see the actual required depth of the footing. This is not an average the entire “blob” would have to be 12 inches deep. By installing in a form, the inspector can determine if the footing meets the code requirement and if it is installed to the designs as shown on the drawings.

Reference

National Building Code 2019 (Alberta Edition), Part 9 Section 9.3.1 Concrete; 9.15.3 Footings

9.15.3.8. Footing Thickness

1. Footing thickness shall be not less than the greater of
   1. 100 mm, or
   2. the width of the projection of the footing beyond the supported element.

Under the CSA Standard A23.1 concrete must be installed into a designed form.

9.3.1.1. General

1. Except as provided in Sentence (2) and Articles 9.3.1.6. and 9.3.1.7., unreinforced and nominally reinforced concrete shall be designed, mixed, placed, cured and tested in accordance with the requirements for “R” class concrete stated in Section 9 of CSA A23.1, “Concrete Materials and Methods of Concrete Construction

6.5.3 Construction

6.5.3.1 General

Forms shall be constructed to meet the requirements for shape, dimensions, and tolerances specified in Clause 6.4. Immediately prior to concrete placement, all forms shall be inspected by the contractor to ensure that they have been erected in conformance with the shop drawings.

9.2 Formwork and formed sections

Forms shall be so constructed that the finished concrete will conform to the shape, dimensions, and tolerance shown on the construction drawings.

Questions can be directed to Safety Codes Services.