Covered Porch Snow Load

[woodman1967]

Hello again

I am working on a covered porch and am wondering about the actual live load on the deck. How much snow load should be applied? The roof will take the majority of the snow load but some snow will blow onto the deck. Could I be safe and ignore the snow load or should I add a portion of the load and how do I determine that portion?

Any help would be appreciated

 

[boo1]

As the porch is open on the (three ?) sides, there should be some drift load. There was a nice snow load thread last year:

http://www.eng-tips.com/viewthread.cfm?qid=185985

 

[ctcray]

Would you ever have more than the 40psf Live load that you'll have on the porch?

 

[MiketheEngineer]

Porch should be designed to meet occupant loads of structure - usually 40 psf live for residential. Unless you live in a "snow" zone - I doubt that you will ever hit that. And I always assume (which may be false) that if there is like 2 feet of snow on a porch - very few people will be out there....

 

[msquared48]

What ctray says is correct. If you anticipated snow load onto the deck is less than 40 psf, the minimum live load for the deck, then just ignore the snow load.

Mike McCann
McCann Engineering

 

[woodman1967]

Thanks everyone,

There are two other things I would like to ask about...wind. I was wondering about uplift in this case, would I treat the porch roof as an overhang?

Also, something I see alot is the deck supported by a continous beam set back up to 12" from the edge of the deck. The support posts for the porch roof are located at the edge of the cantilevered portion of the deck floor. I can't this to work as the joists fail in shear. I would like to see the beam set back maybe 6" and the posts of the porch roof bearing on this beam, and preferably the footing.

 

[CJJS]

I am not sure what you are asking with regard to wind and uplift. I would think the porch would be classified as an OPEN BUILDING per ASCE 7.

You can double the floor joists where the posts bear to help with your shear problem.

 

[rday]

There will be some drifting I would guess.

I believe the IBC requires load combos in chapter 16. Those combos include Dead + Live + (Snow) for allowable stress design. A reduction is permitted for multiple transient loads.

Though I agree, the likelyhood of such a combo in most snow areas is unlikely; to ignore snow load where one exists appears to be a code violation.

For wind, I would go with partially enclosed.