Snow drift at penthouse

[BSE05]

Does anyone have any references for determining the height that roof top equipment or a penthouse has to be above the roof( up on posts with a space below) to prevent any additional load from snow drift.

Our best guess here in the Boston area is one foot, but I would like to confirm this.

 

[civilperson]

No such rule exists. The structure above the roof will block/slow the wind and cause the snow to fall at that location. A two meter horizontal separation for low rise buildings is used for no drift impact from adjoining buildings.

 

[jike]

There is no code or technical reference that I am aware of. It is our obsevation that as long as you leave enough clearance under the equipment, the snow will blow under the equipment instead of creating a drift. We, generally, use the base snow load depth plus am little extra (6" to 12").