Solution To Lower Roof Snow Drift

There was substantial piling of snow on the lower roof.

Solution to lower roof snow drift.

There was so much pile up that our foreman contacted the structural engineer out of concern that the lower roof was overloaded. Leeward caused snow drift would accumulate as well as windward. High flat roof 200ft long no parapet. Density snow density γ.

It should be conservative to use the snow load along the slanted axis of the beam. Snow drift loading lower adjacent roofs. 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. 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.

This approach is conservative and simpler but for small gap the width could be 6 hd. Lower roof is 10ft lower also flat and only 10 ft long. For adjacent drifts we do not start with 4 hdand then possibly increase the width we start with the 1 on 6 shade line. Windward drift results from snow blown against a projection or wall below a high roof.

For ordinary leeward drifts the width is 4hd unless hd hcin which case we set the height at hcand increase the width. Lets assume our project is in madison wisconsin and we have already calculated our balanced roof snow load here. 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. Usually the roadway should be 1 2 feet higher than the nearby landscape to make this effective.

See figure 7 7 from asce 7 10 below for a succinct depiction. Ground snow load s s. Rain load s r. 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.

Version 0 0 2 september 14 2020. Importance factor i s. At what high roof low roof height differential does leeward stop causing snow drift on a lower roof. Leeward snow drifts occur when wind blows snow off of a higher elevation roof down onto an adjacent lower roof.

The snow had slid from the sloped roof and blown backwards onto the lower roof instead of falling straight to the ground. From our example our ground load and flat roof snow load.