Roof Stair Loading 1

[SteelPE]

I have a new project that is approaching completion. The steel frame was erected month ago and most of my work is now done. At least I thought that until the other day when I received another set of shop drawings for a stair to be placed on the roof of the building. I thought I missed this during the design, but as it turns out, I didn't as the stair was recently added. The stair is used to access a roof ladder (at a high/low area of the roof) and goes over some conduit that is attached to the roof or wall (I really don't know and it does not matter).

The question I have would be in regards to the loads on this stair. The code (IBC 2009)requires stairs and exit ways to be designed for 100 psf. I don't see any exception to this. However, since this is used for maintenance purposes only this seems excessive. Roof live load is 20 psf, this seem better, but it's not in compliance with the building code. This issue with applying more load is in relation to the roof structure supporting the stair, I know it will not support the 100psf required by the code. I am going to have a difficult time supporting the addition dead load (weight of a new plinth and dead load of the stair). So I'm trying to reduce the load applied to the roof as much as possible.

 

[dik]

Some codes allow a reduced loading for access to mechanical equipment. Check that area.

Dik

 

[XR250]

100 psf seems excessive. is the stair 3 ft wide or is it narrow?
I doubt I would lose sleep over using 20 psf.

 

[Ron]

SteelPE....you're out of luck, code-wise.....Even OSHA requires the following:


1910.25(b)(6)
Each stair can support at least five times the normal anticipated live load, but never less than a concentrated load of 1,000 pounds (454 kg) applied at any point;

 

[dik]

Ron:

Does the 1000# require any load factor? or, can that be the limit load? Could you use a load factor of 1.05?

Dik

 

[dhengr]

Dik:
I believe that OSHA says the structure, device, system must not fail using the load factor of 5 on anticipated load/design load, or the 1000lbs., it must hold that load. There is no discussion about deformation, etc., as long as it holds the load. Ron’s 1000lbs. is (5)(a 200lb. worker). And, my understanding is that it can fail at 5.0001 or 1000.5lbs.

 

[dik]

dhengr: Thanks, that's what I was hoping.

Dik