Live And Dead Roof Loads In Residential Design

Dead loads consist of the permanent construction material loads comprising the roof floor wall and foundation systems including claddings finishes and fixed equipment.

Live and dead roof loads in residential design.

On a roof with a slope greater than 4 to 12 the live load limit is typically adjusted downward from 20 psf to 15 psf to allow for the relatively greater dead load on the steeper roof. Foot ceiling construction gypsum sheetrock finish 10psf floor construction carpet or vinyl 10 psf hardwood floor 12 psf ceramic tile 15 psf. 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. Light frame 2x12 wood floor with 3 4 inch wood structural panel sheathing and 1 2 inch gypsum board ceiling without 1 2 inch gypsum board subtract 2 psf.

To determine the dead load value for a given floor or roof system the weight of all permanently installed materials in a given component are added together. The values for dead loads in table 3 2 are for commonly used materials and constructions in light frame residential buildings. The load is not shared equally by the supporting structure. Loads used in design load equations are given letters by type.

The bottom line is that the irc requires you to design the roof structure to the greater roof load and in my region that s the ground snow load. Dead loads cont d typical weights of horizontal systems roof construction asphalt shingles 15 psf pounds per sq. Dead loads are given as nominal or asd level. Unlike stiffness live loads and dead loads are added together to determine minimum design values for strength.

Live and dead loads listed in the building code for roofs and floors are approximations of distributed loads. Point loads occur when a weight is imposed on one spot in a structure like a column.