Part 9 Canadian Code Strip Footings

[Woody1515]

Hello everyone,

I have a basic question regarding strip footing design, particularly for Part 9 structures from the NBCC (mostly residential). From my understanding, Part 9 gives design criteria for unreinforced concrete footings. Is it true that if the footing width and thickness meets the Part 9 requirements you can design these footings without any reinforcement? In my limited experience, I've seen many residential drawing packages with rebar in the strip footings.

Thanks!

 

[BAretired]

Yes, it is true. Some engineers may specify longitudinal steel in strip footings, but that is essentially temperature steel. In most cases for Part 9 structures, the width of footing is small. A 24" wide strip footing supporting an 8" thick wall has a projection of only 8" on each side. If the depth is 8", transverse bars are not required.

BA

 

[KootK]

Agreed. In addition to temp and shrinkage, some engineers like that the longitudinal bars make the footing a bit of a beam element to allow the system to span over potential weak bits of soil. Often, however, you'll have a frost/stem wall better suited to that function anyhow though.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[Woody1515]

Thanks for your responses. I figured the rebar included in these footings was "extra". I always find it tough to determine when it is required to design above the Code requirements.