Snow Depth CAN. 1

[palk7 EIT]

Hi,

With NBCC in calculating depth of snow, I see it to be 0.8*SS(Ground Snow)/Density. any reason for reducing it by 0.8? or it should be simply SS/Density?

Thank you

 

[r13]

I guess it is to adjust the loose volume to more densified volume that is corresponding to the snow density. What is SS?

 

[palk7 EIT]

SS ground snow load, on a other thought am thinking it could be roof snow load factor which is 0.8 (Cb)

 

[r13]

I am not sure the two 0.8 factors are related, or could share the same reasoning. Did you check code commentary on ground snow assumptions, which may help?

 

[palk7 EIT]

Attached a calculation example of NBCC, if u see in step 2 in order to determine whether drifting occurs or not they calculate the depth of snow where we have this 0.8

 

[r13]

With NBCC in calculating depth of snow, I see it to be 0.8*SS(Ground Snow)/Density

If the "depth" is the measurement of roof snow, it makes sense now. Since NBCC estimate the roof snow is 80% of the ground snow (0.8Ss). Thus, to calculate the depth of roof snow, it should then be h = Roof Snow/Density = 0.8Ss/Density. Make sense?

Note the roof snow factor, Cb, is not always a constant, as it would be adjusted for roof areas.

 

[KootK]

...on a other thought am thinking it could be roof snow load factor which is 0.8 (Cb)

I believe that to be correct.

 

[palk7 EIT]

Yes got it, thank you !

 

[FishTheStructure]

If the "depth" is the measurement of roof snow, it makes sense now. Since NBCC estimate the roof snow is 80% of the ground snow (0.8Ss). Thus, to calculate the depth of roof snow, it should then be h = Roof Snow/Density = 0.8Ss/Density. Make sense?

Yes, this is how I have always understood it as well.

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

 

[palk7 EIT]

When determining snow drift loads on roof with parapet let's say (2'2") heigh is it acceptable to consider it as a projection in the roof (like mechanical equipments) & calculate it in projection method or it needs to be considered as a adjacent roof (like mult-roof) method and determined in that way? All in Canadian code.

Thank you

 

[jayrod12]

NBCC has a specific section for obstructions, parapet walls would be included in that.

Check out figure G-8 of the commentary if you're using the 2010 edition (WE are still stuck in the 2010 edition where I practice normally). For the 2015 edition I believe it is included directly in the main part of the code where snow loading is discussed

 

[r13]

Fish,

Thanks for confirming my lucky call. My first guess was off the base though