WOOD BEAM SIZINGTM   Snow loads

Wood Beam Sizing calculates roof loads based on the ground snow load and the roof choices selected at the PLAN module. All loads are equivalent uniform loads -- eqL, pounds per square foot.

EQUIVALENT SNOW LOAD

For headers and rafters, WBS Basic follows the IRC code and uses either the ground snow load or the minimum roof load, whichever is greater.

For headers, the following results are shown at the WEIGHT module. For example, with roof pitch of 12-in-12:

GROUND SNOW

Ground snow load (psf) is the maximum weight of snow, on the ground, expected in a 50-year storm, and are updated with each new edition of ASCE 7. Building code maps show the required ground snow load.

FLAT ROOF

Flat roof snow load is a calculated estimate of the weight of snow expected on a flat roof, taking into account the building location, exposure and roof insulation as entered at the PLAN module.

SLOPED ROOF

Sloped roof snow load (balanced load) is the calculated weight of snow for the roof pitch you entered, with a portion of the snow sliding off.

UNBALANCED LOAD

Unbalanced snow load (psf) is the simplified calculation method of ASCE-7, assuming uniform ground snow load on one half of the roof.

SNOW LOAD with drift

The most complete ASCE 7 calculation method which models wind driven snow drifts, with more snow on the side away from the wind.

MINIMUM ROOF LOAD

Code mandated minimum live load to account for workers and construction materials, based on roof slope and tributary area. Never less than 12 psf.