Snow loading

[bill mart]

Saw the posting from earlier with the barn about to fall down from snow load. What is the minimum pounds per square foot rating in your towns? I think its 55 lbs. in my town. Bill M.

 

[JDemaris]

I don't know how many towns have their own specs - but most counties in the US are using some version of International Building Code adopted by their state. Different states use different versions or years. I'm in New York and I think we're up to Uniform Code version 2003.
Snow load is not a fixed number. It's dependent on the type of use the building sees, pitch, type of material, etc. so there's quite a lot too it.
For the most part, a residential structure here where I live must have a 60 lb. snow-load rating. A few years ago it was 40 lbs. Our area gets 8 feet of snow per winter on average.
I have property in the Adirondacks with a 12 feet per year average and residential structures must have an 80 lbs. snow-load rating.
Personally, I don't build anything in snowy regions with less than a 100 lb. rating. It's cheap insurance.

 

[1936]

Weather service stated that one sq ft of snow wt. is 5 pounds. The non wet type. Only 50 inches on my drive this winter and two inch for casted this night. 38 inches is the average. For casted a HOT summer.

 

[Ultradog MN]

Just went through that with my local building inspector as I'm planning to vault part of the roof in my house.
Code here is 55 lbs/foot

 

[Anonymous-0]

There are two types of snow load in the IBC. Roof snow and ground snow load. The snow loads referred to in this column are probably ground snow loads. When someone states a snow load of 60lbs it is definitely ground snow which is usually twice the roof snow load. If you want the more actuate number ask for the roof snow because that's the one that counts. We build buildings and I always give the customer both ratings.

 

[Jerry/MT]

Realistically, walking on your roof puts a very high load on the roof. I weigh near 200 pounds and I doubt the area of my shod feet is greater than 1 sq ft total. So I reckon my load standing on the roof is close to 200 lbs/sq ft. I think a properly designed roof has more strength then the rating number implies. My roof is designed for 80 lbs/sq ft snow load and it feels very solid when I walk on it.
I think these ratings are "deflection limited" ratings not ultimate strength of the roof. By that I mean that that if you take all the loads including the snow load, the maximum deflection of any structural element is no greater than say 0.25 inches.