Unbalanced Snow
Unbalanced Snow
(OP)
ASCE 7-98 has the greater value of Unbalanced Snow placed at the eave.
ASCE 7-06 & 7-10 have the greater value placed at the ridge.
Nature did not change – our interpretations did.
Side-note: In Wisconsin, we have an allowance to use what is called an “Alternate to the requirements of IBC section 1608.1”, which reduces the resultant unbalanced snow load pressures obtained by the IBC and ASCE method.
Since there is an apparent difference of interpretation, conservatively and for simplicity and expediency, I apply the greater snow pressures over the entire width of the structure. Although this seems overly conservative, which may result in higher cost, since my supervisor has instructed me to pursue this direction, and it does exceed minimal requirements of IBC and ACSE, I am comfortable with this decision, in addition, since experienced estimators of the general contractor client have rarely scoffed at any structural member sizes I have specified over the past years, since the adoption of IBC, that are related to unbalanced snow.
What are your opinions or wisdom regarding this?
What practices do you use? How do you apply unbalanced snow?
Thank you all!
ASCE 7-06 & 7-10 have the greater value placed at the ridge.
Nature did not change – our interpretations did.
Side-note: In Wisconsin, we have an allowance to use what is called an “Alternate to the requirements of IBC section 1608.1”, which reduces the resultant unbalanced snow load pressures obtained by the IBC and ASCE method.
Since there is an apparent difference of interpretation, conservatively and for simplicity and expediency, I apply the greater snow pressures over the entire width of the structure. Although this seems overly conservative, which may result in higher cost, since my supervisor has instructed me to pursue this direction, and it does exceed minimal requirements of IBC and ACSE, I am comfortable with this decision, in addition, since experienced estimators of the general contractor client have rarely scoffed at any structural member sizes I have specified over the past years, since the adoption of IBC, that are related to unbalanced snow.
What are your opinions or wisdom regarding this?
What practices do you use? How do you apply unbalanced snow?
Thank you all!






RE: Unbalanced Snow
You are obligated to use at least as much load as specified for the code edition in question, but realistically a large percentage of the country is now on IBC 2012 or 2015, both of which follow the ASCE 7-10 version of the Specifications.