Minimum Live Load - Structure on a Roof

[aokamura]

Hi,

Can anyone tell me what the minimum live load is for a roof structure (utility room, electrical room, supplies closet, etc)? It's not in ASCE 7-02 and not on any other forums, either.

Thanks!

 

[msquared48]

I would use 40 - residential - for utility Janitor's closet)and supplies. If there is going to be a lot of paper products stored in the supply room though, I would consider higher - look to the psf weight of the paper stored.

Electrical room, 40 also (with wall panels only) unless there was heavy equipment, then look to the weight of the equipment, or 75 psf minimum.

Mike McCann
MMC Engineering

 

[aokamura]

Hi Mike,

Thanks for your advice.

Is there a minimum point load as an alternative?

 

[msquared48]

I have not heard of any for the roof, but if there is equipment to deal with, I would look to those reactions as point loads if applicable.

Mike McCann
MMC Engineering

 

[BAretired]

I think you should use a roving point load of 1000# which could occur anywhere.

BA

 

[Ron]

The minimum live load for a roof is 20 psf. If the structure is an appurtenance to an existing roof (like a penthouse), then the "floor" load of the penthouse will be added to the roof load of the larger roof. I believe that is what Mike is addressing.

Since this is likely a small roof area, most likely no live load reductions would apply.

If you check Table 4-1 of ASCE 7-05, you could probably rationalize a 2000 lb point load for your application, assuming I'm understanding your posting.

A sketch would be helpful.