Roof Design Loads Snow

Simple design check representative of worst case combined axial and transverse loading.

Roof design loads snow.

Roof snow load nbc 2010 roof snow load nbc 2010 version 0 1 0 december 31 2020. Proper roof ventilation and high r value roof insulation is essential to minimizing ice dam formation. These new metal roof designs have chimneys to make a fireplace in the room for keeping the house warm during cold winters when the snow fells from the sky. I importance factor.

The two directions of wind that cause snow drifts are windward and leeward. See table 2 9 for importance factor values depending on the category of the building. In a 6 inch snowfall an inch of snow has a design density of 1 25 psf per inch and a real world density closer to 1 psf per inch. These roof designs also come with insulations and metal of the roof plating is glazed with the snow retention techniques which keeps the coldness of the snow outside and repel the snow from the rooftops.

Loads nbcc 2015 snow. If the design necessitates a roof slope that drains onto a traffic area snow retention devices should be provided to hold the snow in place. Shed dormers are easier to waterproof and shed snow better than gable dormers. As you might expect buildings of high importance such as power plants schools or hospitals need to be more snow resistant and so can withstand a higher load.

Note that the density of snow increases as depth increases. Estimates for the actual weight of snow range from 1 to 1 5 psf per inch of depth. Geometry of the roof and the direction of the wind are the two drivers that lead to snow drifts. Roof snow load snow drift load step snow drift load obstruction wind.

Or the truss could be designed based on the assumption that the 25 psf roof snow load is a factored ground snow load in which case a ground snow load is back calculated using asce 7 based on the specified roof snow load pg 25 psf. Snow design loads are based on figures published by the asce. Less snow will accumulate on a slippery roof it will slide off instead. After you obtain the roof slope factor from those sections in asce 7 10 the balanced design snow load for the sloped roof can easily be calculated using equation 7 4 1.

Axial forces from snow loads and roof live loads should usually not be considered simultaneously with an extreme wind load because they are mutually exclusive on residential sloped roofs. р f design flat roof snow load. р s design snow load for a sloped roof. If your structure has a sloped or flat roof you still need to calculate the flat roof snow load.

In some cases roof snow melt systems or heat tape can be used to combat ice accumulation on eaves and in valleys. This is the snow load calculated in the previous section. The balanced snow load is applied everywhere where the roof structure is located. р g ground snow load.

Primary structure fig 4 1 7 6 a walls fig 4 1 7 6 b. Slipperiness of the roof. According to asce 7 16 the design snow loads for flat roofs and sloped roofs can be obtained using the following equations.