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Area of column footing when joist span exceeding 4.9 m

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sunyaer

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Apr 21, 2022
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338
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Toronto
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9.15.3.4. Basic Footing Widths and Areas
...
(2) Where the supported joist span exceeds 4.9 m in buildings with light wood frame walls, floors and roofs, footing
widths shall be determined according to,
(a) Section 4.2., or
(b) the following formula:
W = w • [ Σ sjs / (storeys • 4.9)]

...

(3) Where a foundation rests on gravel, sand or silt in which the water table level is less than the width of the footings
below the bearing surface,
...
(b) the footing area for columns shall be not less than twice the area required by Sentences (1) and (2), and
Article 9.15.3.7.
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Questions:

1. Is footing area of columns permitted to use the formula of (2)(b) to calculate when supported joist span exceeding 4.9 m? (Note: 9.15.3.4.((3)(b) references 9.15.3.4.(2) for footing area)

2. In reality, columns would support beams and beams support joists, while the beam span would be the column spacing as in the table 9.15.3.4, is this understanding correct?
 
Can't tell without more code text but 9.15.3.4 seems to be about basic spread footings supporting (typically) a stem wall, sill plate, and joists bearing directly on the sill plate. 1. Don't know for longer joist spans but 4.9 meters bearing is a 32' joist, uncommonly long for a dwelling typical of this construction. 2. I sense to that column loads and their footers at elsewhere in the code.

Is this code available for free viewing on online?
 
Last edited:
1. correct. It just details how to interpolate.

2. Correct. There is similar interpolation possible for column areas based on column spacing.
 
The footing area is .4m2 for one storey and 3m spacing between columns. 0,75m2 for two storeys, 1.0m2 for three.
Interpolate for greater spacings. I see this missed on plans regularly.
 
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