Factory Mutual metal deck span limits

[tw]

Is there any reason to pay attention to the (more restrictive) metal deck span limits from Factory Mutual for normal commercial construction? The CSI deck catalog I have gives them in their tables and they have a Factory Mutual approval guide at:

http://www.metaldek.com/product_details.asp?id=49

I've only had to work with Factory Mutual requirements one time at an industrial facility and this is the first time I noticed it in deck catalog.

tw

 

[jike]

I believe this criteria was developed to control deflections of metal deck roofs. This was especially important with the unforgiving nature of built up roofs.

I still try to limit my spans in all buildings to similar maximums even though we are using rubber membranes on most roofs today.

 

[JAE]

Factory Mutual is technically only required if the building owner is insured by Factory Mutual, or if the owner is insured by a company that references Factory Mutual.

It is FM's attempt to control and minimize claims by stepping into the design of buildings and ensuring a level of conservatism in construction of their insured buildings.

If you owner isn't covered by an insurance company that requires this, then you don't need to follow it....unless you want to as its provisions are usually pretty good.

 

[haynewp]

I have had to do all the extra FM stuff a while back and JAE is right. But, I don't think I would follow the FM manual if the roof did not need to be insured by FM, unless I got the OK from the owner to do so. I remember parts of the wind and live load provisions being pretty conservative over what the code required for me.