Determining if a Fabric Roof is "slippery"

[Cambridge99]

I would like to determine if a fabric roof is slippery for a snow load calculation.

The following is a quote for ASCE-7 (C7-4 around page 317):

"It is difficult to define “slippery” in quantitative terms. For that
reason a list of roof surfaces that qualify as slippery and others
that do not, are presented in the standard. Most common roof
surfaces are on that list. The slipperiness of other surfaces is best
determined by comparisons with those surfaces"

Does anyone know where this list of roof surfaces is in the standard?

 

[flight7]

In the 2005 edition, there is a list in paragraph 7.4, but fabric isn't listed.

 

[RHTPE]

I would be cautious on this topic. I built a 30' x 50 pavilion that utilized a tarp for the roofing (it started as a temporary structure). Roof pitch was about 5V:12H. The first year the snow practically slide off by itself. The second year it required a little more encouragement. The third year it required a lot of encouragement to slide off.

The problem you have is that environmental "dirt" will accumulate on the fabric - things like dust & pollen. Rain will wash some of this off early on, but as time goes on it will accumulate. This accunulation will give the surface a bit more "tooth" and resist the tendency for the snow to slide.

Of course, all will depend on the roof's pitch, but with this season's snowfall here in New England I've seen many 12v:12h roofs with a substantial depth of snow cover.


Ralph
Structures Consulting
Northeast USA