A longer term solution to drifting snow includes building up roads and driveways so that snow is blown across rather than drifting on to them.
Solution to lower roof snow drift.
If the drift width w exceeds the width of the lower roof the drift shall taper linearly to zero at the far end of the lower level roof to me this makes the most sense when talking about a leeward drift as in my case meaning the 3 drift tapers down to zero at the edge of the canopy.
There was so much pile up that our foreman contacted the structural engineer out of concern that the lower roof was overloaded.
By elevating driveways above the surrounding terrain wind will sweep snow off of the roadway.
Snow drift loading lower adjacent roofs.
There was substantial piling of snow on the lower roof.
For adjacent drifts we do not start with 4 hdand then possibly increase the width we start with the 1 on 6 shade line.
If you believe that this roof will be less likely to clear then you might want to consider using a value closer to the flat roof snow load.
Lets assume our project is in madison wisconsin and we have already calculated our balanced roof snow load here.
Windward drift results from snow blown against a projection or wall below a high roof.
The snow had slid from the sloped roof and blown backwards onto the lower roof instead of falling straight to the ground.
Snow drift loading lower adjacent roofs.
At what high roof low roof height differential does leeward stop causing snow drift on a lower roof.
Lower roof is 10ft lower also flat and only 10 ft long.
Density snow density γ.
Shaped drift to that for a roof step with the same fetch and ground load 50 faq 4 odd drift geometries approach used for gable roof drifts in 7 05 area for roof step d for a triangular gable drift with a 1 s slope areas match 51 faq 4 odd drift geometries roof step with a sloping lower level roof h d is drift height for windward or leeward.
See figure 7 7 from asce 7 10 below for a succinct depiction.
Leeward caused snow drift would accumulate as well as windward.
Typically the windward drift height hdw is less than the leeward drift height hdl unless the length of the lower roof is considerably longer than the length of the upper roof.
Leeward snow drifts occur when wind blows snow off of a higher elevation roof down onto an adjacent lower roof.
Importance factor i s.
It should be conservative to use the snow load along the slanted axis of the beam.
Version 0 0 2 september 14 2020.
Rain load s r.
For ordinary leeward drifts the width is 4hd unless hd hcin which case we set the height at hcand increase the width.
Usually the roadway should be 1 2 feet higher than the nearby landscape to make this effective.
High flat roof 200ft long no parapet.
