Live Load On Flat Roof

This downward imposed load on the home is also known as the snow load.

Live load on flat roof.

The north zone middle zone and the south zone are identified on the roof load zone map above. Roof load live load design is affected by the shape of the roof whether it is flat curved or pitched. Calculating the load on a flat roof is a challenging task for the layperson that involves knowledge of building materials their weights and local building codes. Used but they typically defined the load cases or combination stress or strength limits and deflection limits.

Roof loads are a downward vertical force on the home. The live load on a roof is the weight of any temporary objects on the roof. Ordinary flat pitched and curved roofs and awnings and canopies other than of fabric construction supported by a skeleton structure are permitted to be designed for a reduced uniformly distributed roof live load l r as specified in the following equations or other controlling combinations of loads as specified in section 1605 whichever produces the greater load effect. Load types loads used in design load equations are given letters by type.

D dead load l live load l r live roof load w wind load s snow load e earthquake load r rainwater load or ice water load. Live loads on roofs table 1 3 gives lives loads on flat roofs sloping roofs and curved roofs. Further in most areas of the united states design winds are produced by either hurricanes or thunderstorms. Step 4 determine the flat roof snow load.

The standard guide in the u s the asce 7 05 lists weights and stresses for all building materials expressed in pounds per square foot. In other words on a steep roof less material would be stacked in a concentrated area at one time to avoid having it slide off. Roofs of buildings used for promenade or incidental assembly purposes shall be designed for a minimum load of 400 kg m2 4 kn m2 or heavier it required. 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.

In my region on cape cod we have a ground snow load design of 25 psf which is a greater design load than the live load 12 psf to 20 psf over an entire roof system.