Snow Load And Tensile Roof

Or the 25 psf snow load could be entered as a roof snow load with the unbalanced snow loading option turned off.

Snow load and tensile roof.

When discussing snow load with anyone it is crucial to have a clear understanding as to if the load is a ground or flat roof snow load. Snow load is an environmental load not a live load section 1602. Snow loads are influenced by elevation general weather and moisture patterns slope direction exposure roof or trail bridge configuration and wind direction and severity. One inch of snow is equivalent to a load of approximately 0 5 psf but may be higher when the snow is denser.

Oregon requires a minimum roof snow load of 20 psf pm in asce7 for all roofs plus a 5 psf rain on snow surcharge for many roof types resulting in a 25 psf minimum roof design load for most roofs. Therefore the reduction of live loads for tributary area in section 1607 11 2 is not permitted. When snow is plowed into piles on the structure or if ice accumulates due to clogged drains this load can be exceeded. You can also find the load per square meter or square foot of roofing by opening the advanced mode.

Wind load a procedure for estimating the wind pressure applied to buildings is presented in section 6 of asce 7 05. Snow can either blown from the low side of the roof towards the high side or is blown off the higher area of the roof onto the lower projected side. Only the properly adjusted loads can be used to design roof structural elements. Garages are normally designed for a roof live load of 60 to 80 pounds per square foot.

The amount of additional snow load or surcharge depends on the difference in height of the two adjacent roofs and the lengths of roof perpendicular to the drop in height. Victor staley a building official in the town of brewster mass responds. Overestimation of snow loads can unnecessarily increase the cost of construction. This issue of live load vs.

Snow piles can become far heavier if rain occurs after the pile is in place and as noted snow that is compacted and piled by a plow can. See the map usage notes or snow load analysis for oregon part. Pf is flat roof snow load if as a consumer your concern is snowfall and you want to upgrade the ability of your building to carry it this is the value to increase. If you want to calculate these values by hand use the following formulas.

Ground snow load might seem somewhat confusing until you read the basic premise that is identified in irc section r301 6 which states. The roof shall be designed for the live load indicated in table r301 6 or the snow load indicated. Snow load thickness density. If unbalanced snow loading isn t required or specified the truss designer may enter the 25 psf snow load as a top chord live load tcll set the load duration factor to 1 15 for snow and turn snow loading off completely.