Two ansi standards appear to cover attic ladders.
Attic design loads.
Girder load width half joist span live load on roof local requirements for wind and snow.
Attic truss analysis the truss shown below is known as an attic truss or a room in attic truss.
2attic loads may be included in the floor live load but a 10 psf attic load is typically used only to size ceiling joists adequately for access purposes.
Ft dead load of roof of wood shingle construction 10 lbs.
The ceiling load may include items like drywall ducts recessed lights bathroom fans and attic insulation.
However if the attic is intended for storage the attic live load or some portion should also be considered for the design of other elements in the load path.
The minimum design load is given in section 4 2 1 1 of the ansi a14 3 standard.
Attics that have no flooring unless expressly built so an attic s joists are meant for carrying the load of the ceiling below and related elements collectively known as the dead load.
When used for storage only dead load of attic floor not floored 10 lbs.
Analysis of an attic truss requires multiple load cases with multiple duration factors.
This type of truss carries a combination of roof l r or s and floor l loading in addition to the standard top and bottom chord dead loads.
This section states that the minimum design live load shall be two loads of 250 pounds each concentrated between any two consecutive attachments.