Parapet Walls with kicker and Snow Drifts

[VBI]

What effect would raising a parapet wall height have on snow drifts on the "existing" roof structure? A one story store is raising the parapet (from 4' to 6') with light gage framing and a kicker at a 45 degree angle which I guess sheds the load immediately adjacent to the parapet. I was wondering if larger snow drifts should be considered. THANKS in advance for any thoughts...

 

[JAE]

VBI - it depends.

In the US, for most cases, a parapet snow drift won't exceed 4 feet so raising the parapet height to 6 feet would not change the snow condition.

That is because snow drifting is a function of roof width. The parapet height only serves to limit the maximum drift that can occur.

A set roof width will result in a drift on a parapet. If the parapet is higher than that drift height, then raising the parapet theoretically changes nothing.

 

[FoxSE14]

Don't forget about wind...

 

[a2mfk]

Been a long time since I did anything with snow, but wouldn't the 45 degree kicker push the snow drift back towards the middle of the span? It may be insignificant but worth a quick check...

 

[BAretired]

Check out some of these links:

http://www.google.ca/search?hl=&q=p...rlz=1B3GGLL_en-GBCA404CA404&ie=UTF-8&aq=0&oq=

BA

 

[msquared48]

I don't see that kickers are lickely to affect the snow drift at all.

Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask

 

[BAretired]

If the kickers are covered by a deck, they create a void space with triangular cross section below, so the snow which would have occupied the void space is not going to be there. Any snow lying on top of the sloping deck will be supported as two line loads rather than a distributed load.

If the kickers are not covered, they will not affect snow load.

BA

 

[msquared48]

Makes sense BA. Thanks.

Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask

 

[VBI]

Thanks all for your comments. My analysis came up with a calculated snow drift of 2.63ft based on Figure 7-8 of ASCE-07. However, the clear height from the top of the balanced snow to the top of the parapet is 3.41ft. I do think that the 2.63ft controls and that the high parapet does not inclrease the snow drift height (load). Is that a fair interpretation. Parapet is located on Long Island, New York. Thanks again.

 

[BAretired]

I would expect a six foot vs. four foot high parapet to make a difference in drift load, but I would be using the National Building Code of Canada, not ASCE.

BA