Bar Joists for Floor Support of an MOB

[mlzahn]

I'm thinking of using steel bar joists for second floor support of a two story Medical Office Building in Southern California. I was also thinking of using wood sheathing on metal deck for the second floor. Is there anyone out there that thinks I shouldn't? I've seen the type of construction before, but not often. I'm thinking it would be cheap. Any comments are appreciated.

 

[BAretired]

I am one who thinks you shouldn't. Why would you use wood sheathing on metal deck? You could use wood deck by itself if it meets your fire code. You could use concrete on composite metal deck. But in what circumstances would you ever use wood sheathing on metal deck? Damned if I know!

BA

 

[SteelPE]

I think I have seen it done before.... but not often. I can't specifically remember why the system was used. It might have something to do with being able to get higher loads/spans out of the metal decking vs plywood. Then you just use plywood over the top to make it level. One thing you do get is much lighter dead loads on the structure vs a deck/concrete floor.

I will say that I have mostly seen this application used for industrial applications not for an office building.

 

[dcarr82775]

I have seen it done in places where it is just to hard to get concrete into the location. The deck allows for larger spans and the plywood levels it out. Only in non-public spaces, I wouldn't do it in a public space like an office building

 

[JAE]

In some building types you cannot use flammable material as a structural element. We've come across this in industrial warehouses where use of wood studs, joists, plywood is not allowed to support loads.

In these cases, say a small office "shack" on a loading dock, we use light gage steel studs and joists, place a metal deck over it and then cover with plywood so the owner can use the "ceiling" to store materials, etc.

 

[mlzahn]

Thank you to all who responded!

 

[spats]

I would be concerned about floor vibration, given the low mass. Also, if you have operating lights mounted below the floor slab, the light weight would also be detrimental to the operation of the lights.

 

[Teguci]

Are we talking just medical offices or are we putting medical equipment in these rooms? There are some medical devices (med gas booms, rad shields, lights, etc..) that are very sensitive to deflections and rotations (0.2 degrees under moment loads). Also, some patient tables place significant point loads on the floors.

 

[SteveGregory]

This floor system is susceptible to vibration from both the bar joist spans and the metal deck w/plywood spanning between the bar joists. It is likely to be a "noisy" floor also. I've seen this system before and a variation using grating instead of metal deck. The poor guy in the cubicle next to the aisle had a hard time watching his computer monitor bounce up and down when someone walked by.

Fortunately, our firm was not responsible for this design!

 

[MrHershey]

I would be really concerned with vibration with that kind of system. Generally would be much more comfortable with deck+concrete topping.