Roof Projections And Parapets Snow

The drift on the upwind side of rooftop units rtus is a windward drift as it is for parapet walls.

Roof projections and parapets snow.

Superpose the drift load on the base snow load. For simplicity asce 7 16 requires a windward drift on each side of the unit based on the larger of the two fetch distances. Parapets can be both a safety feature designed to stop falls from the edge of the roof and also a constructional and stylistic feature a large percentage of flat roofs also feature a parapet of some height. Check for ice dams and icicle loads.

Generally the wind will create snow buildup against higher surfaces e g. Drifting snow generally causes large loads at relatively concentrated locations on buildings and other structures when compared to flat snow loads that blanket an entire roof area. Check for loads due to snow sliding from an upper roof. 20 ft of the roof multiply the drift load by the factor.

Section strength bolted connection lag screw withdrawal. Fig i 7 fig i 8 fig i 23. Roof snow load snow drift load step fig. For roof projections l u shall be taken equal to the greater of the length of the roof upwind or downwind of the projection 33 outline minimum roof snow load thermal factor unbalanced load drift load on adjacent roof parapet wall rtu drift sliding load on adjacent roof ponding faq s 34 sliding load on adjacent roof sliding load on lower roof in 7 05.

Section column axial compression web crippling stiffener steel column baseplate. Walls and parapets drifts on lower roof sections snow accumulation deposits in roof valleys and drifts on the leeward downwind side of objects obstructions and ridges known as aerodynamic shading figure 8. See section 7 9 asce 7. Parapets often go unnoticed on modern houses as they can appear as the line of a flat roof.

Done calculate drift surcharge load. About terms of use faq subscribe contact us accessibility. 20 s 20 where s is the spacing in feet. G 5 snow drift load obstruction fig.

Parapets on modern roofs.