Canadian Code - Part 9 Snow Drift Loading

[Signious]

Hello All,

In CBC 2005 / AlbertaBC 2006 I cannot find any provisions for snow drift loading, or any clause telling you to go over to Part 4 loading (besides 9.4.2.2 (3) - Bow string, arch, or semi circular roof trusses ... (use) Subsection 4.1.6)

Is this an oversight on the part of NRC? With some of the 'interesting' hip-valley roofs I've been seeing in residential, drifting should be a concern.

Thoughts?

 

[canwesteng]

Roof trusses should be stamped/designed to part 4 no? I don't do any residential design though. The extra snow is unlikely to be critical for foundations or load bearing loads I would think

 

[FishTheStructure]

I think you will find that everyone on this forum that works in Canada likely designs to Part 4...

Great spirits have always encountered violent opposition from mediocre minds - Albert Einstein

 

[BAretired]

See Article 9.4.2.5 Roofs at different levels.

BA

 

[Signious]

Thanks BA,

Not sure how I missed that. Was just looking for backup in a disagreement with a truss supplier's design when I gave loading done by Part 4 - and this is exactly what I needed.

 

[SkiisAndBikes]

I would recommend reading the related clauses on Part 9 snow loading in the Appendix A commentaries. It gives more insight into when and how they have assumed Part 9 snow loads should be applied, given different roof sizes and geometry. As with anything, engineering judgement should be excercised.

 

[ergus]

Article 9.4.2.5 must only be in the Alberta version of the code, it is not in my versions of the NBC or the B.C. version of the code. What does it say ?

 

[BAretired]

I don't believe the Alberta Code differs from the NBC respecting snow load. The OP mentioned Alberta Building Code 2006 which may not be the latest version. It reads as follows:

9.4.2.5 Roofs at Different Levels

If roofs are at different levels, or there are projections above the roof level, the design roof snow load shall include allowance for the effects of drifting snow in accordance with Part 4.

BA

 

[jayrod12]

There's no 9.4.2.5 in my 2010 NBCC

 

[Signious]

Yesm 9.4.2.5 is omitted in 2010 NBC, but is in 2006 Alberta Code.

Unfortunately Alberta hasn't issued anything bringing provincial code up to 2010 NBC standards. There are various issues with the new energy efficiency requirements that everyone is fighting over.

 

[KootK]

AB2014 is due out this May. Well, overdue really. Six month grace period by the sound of it.

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.

 

[Signious]

Do you have a link for that KootK?

I was talking with Diana McQueen a month or so ago and she made it sound like it was further off than that.

 

[KootK]

No, I'm afraid that I don't. This is just what we hear from our Safety Codes Council friends.

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.

 

[BAretired]

If a clause similar to 9.4.2.5 is not included in the latest code, it would appear to be an omission.

BA