The tabulated rafter spans assume that ceiling joists are located at the bottom of the attic space or that some other method of resisting the outward push of the rafters on the bearing walls.
Irc attic dead load.
Maximum ceiling joist spans.
Attic joists for live loads attic joists that are made from 2x8s may be acceptable for building your attic floor but because every room is variable there are no absolutes.
International residential code chapter 3 building planning table r301 4 irc interpretation no.
Load combinations provide the basic set of building load conditions that should be considered by the designer.
Flooring for dead loads may not be sufficient for live loads the loads created by people and the features of living space.
International residential code 2015 irc 2015.
The material and component weights tables 1 3 and 1 4 may help builders correctly size.
Wide by 42 in high rectangle within plane of truss for two or more adjacent trusses top of required insulation roof trusses 24 in.
The weight of the materials of construction incorporated into the building including but not limited to walls floors roofs ceilings stairways built in partitions finishes cladding and other similarly incorporated architectural and structural items and fixed service equipment.
International code council 42 in.
Therefore additional calculations typically are not required.
Top of required insulation bottom chord of truss designed for live load 20 psf and dead load 10 psf bottom chord of truss designed for live load 10 psf.
The minimum uniformly distributed live load shall be as provided in table r301 4.
The international codes i codes are the widely accepted comprehensive set of model codes used in the us and abroad to help ensure the engineering of safe sustainable affordable and resilient structures.
Dead loads are defined by the code as follows.
Dead load 5 psf.
Attic access hatch minimum 24 in.
The load combinations in table 3 1 are recommended for use with design specifications based on allowable stress design asd and load and resistance factor design lrfd.
11 04 2000 edition issued.