Snow Load On Sloped Roof

The flat roof snow load is calculated using formula 7 3 1.

Snow load on sloped roof.

It is determined based. Ground snow load value. Discount that actual snow loads may exceed them only that the risk of snow load induced failure is reduced to an acceptably low level. Thus as the roof gets steeper the rafter gets longer and the weight of roofing materials increases.

If the snow weighs 10 pounds per cubic foot and there are 1 5 feet on the roof each square foot of the roof is getting 15 pounds of pressure. P s c s p f the thermal factor c t from table e 3 determines if a roof is cold or warm slippery surface values shall be used only where the roof s surface is unobstructed and sufficient space is. If your roof is 1 000 square feet the total snow load is 15 000 pounds of snow. Other considerations for sloped roofs can be found throughout chapter 7 of asce 7 10.

Snow loads are influenced by elevation general weather and moisture patterns slope direction exposure roof or trail bridge configuration and wind direction and severity. It makes sense when designing a metal roof to shed snow not to keep it on. To figure out the load on your roof take the depth of snow in feet and multiply it by the weight of a cubic foot of snow. Roof snow load is defined as the weight of snow on the roof surface used in design of the building structure ibc 2012.

It is critical that a designer specify enough snow retention devices based on the slope and snow load. You get the same load as a flat roof with the same run would get. For locations where 0 pg 20 psf all roofs with a slope w 50 with w in ft shall have a 5 psf rain on snow surcharge. There are also factors such as deflection elasticity and wood species that come in to play.

This rain on snow augmented design load applies only to the balanced load case and need not be used in combination with drift sliding unbalanced or partial loads. Consult local building codes for snow load capacity and reference the span tables for joists and rafters published by the american wood council awc as a general rule roofs that have a high human occupancy rate should be framed with rafters every 16. With expansion and contraction of the metal it is difficult to attach snow retention devices into the roof decking without causing a roof leak or slotting of the. Actually with snow you don t get more load along the slope of the rafter.

If you live in the us our snow load calculator compares the total weight on your roof with the permissible load calculated according to the standards issued by the american society of civil engineers regarding the minimum design loads for buildings and other structures asce7 16. The snow load that is applied to our structure is not the ground snow load but in most cases the flat roof snow load. Overestimation of snow loads can unnecessarily increase the cost of construction. Underestimation of snow loads can result in premature failure high maintenance costs.