Solution To Lower Roof Snow Drift

When wind blows snow from one roof area to another snow drifts form on the lower roof in the wind shadow of the higher roof creating an unbalanced load.

Solution to lower roof snow drift.

Windward drift results from snow blown against a projection or wall below a high roof. See figure 7 7 from asce 7 10 below for a succinct depiction. Snow drift loading lower adjacent roofs. This approach is conservative and simpler but for small gap the width could be 6 hd.

Lets assume our project is in madison wisconsin and we have already calculated our balanced roof snow load here. Ground snow load s s. For ordinary leeward drifts the width is 4hd unless hd hcin which case we set the height at hcand increase the width. From our example our ground load and flat roof snow load.

This drift reducing effect on the lower step is included in the 1995 nbcc calculation by the 6 γ h p s s 2 term. Usually the roadway should be 1 2 feet higher than the nearby landscape to make this effective. Of higher level roof in asce 7 05 roofs a b c all get drifts 26 drfit load on adjacent roof in reality drift only if lower roof in wind shadow of upper roof in asce 7 10 we assume a 1 v to 6 h wind shadow after tabler s work on snow fences 27 drift load on adjacent roof. Version 0 0 2 september 14 2020.

By elevating driveways above the surrounding terrain wind will sweep snow off of the roadway. Truncated drift required if lower adjacent roof within 20 ft. Sloped retrofit metal roofing solution for lower roof. Solutions to these problems are generally self evident e g place air intakes high up on the wall keep windows at roof steps as high above the lower roof as possible locate plumbing vents and.

The following table provides an. Leeward snow drifts occur when wind blows snow off of a higher elevation roof down onto an adjacent lower roof. 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. Rain load s r.

Snow melt ponding adds to the load and may also cause water damage and leaks at the intersection. Density snow density γ. For adjacent drifts we do not start with 4 hdand then possibly increase the width we start with the 1 on 6 shade line. 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.