Finished attics need stairs that meet all of the standard staircase requirements.
Finished attic wieght limit.
It is vital to observe the weight rating and make sure that you comply with it at all times.
In general stairs must be at least 3 feet wide and provide at least 6 feet 8 inches of headroom.
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.
Observing the weight rating.
Dead load weight of roof trusses top chord bottom chord webs weight per lineal foot plf 2x4 2x4 2x4 4 3 2x4 2x8 2x4 5 6 2x6 2x4 2x4 4 8 2x6 2x6 2x4 5 5 2x6 2x6 2x6 6 2 2x6 2x8 2x4 5 9 2x6 2x10 2x4 6 6 2x6 2x10 2x6 7 2 2x8 2x8 2x4 6 6 2x8 2x8 2x6 7 2 2x8 2x10 2x8 8 4 dead load weight of floor trusses depth in inches top chord bottom chord.
Building codes typically require that a finished space have a ceiling height of 7 feet 6 inches over at least half of the available floor space.
To simplify you can place 20 pounds of dead load per square foot on your subfloor as long it s supported mid span.
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.
This is where dreams of adding new living space in an attic are often abandoned.
This is because the ladder is simply not strong enough to support any more weight and you are putting unreasonable pressure on the attic access ladders every time you break the weight limit.
Stairs can take up a lot of space in both the attic and in the floor below so they are important considerations for planning.
The international residential code on which most local building codes are based requires that floors in non sleeping rooms must support a minimum live load of 40 pounds per square foot and floors in sleeping rooms must be able to handle a live load of 30 pounds per square foot.