Roof Metal Decking Flexible Diaphragm Value 1

[candy0727]

I have a Cold-formed light gage steel framing project and It will be metal roof decking system without filling LT. WT. concrete over metal roof rafters.
1.Can it be considered a flexible diaphragm?
2.Do anyone know diaphragm value of this system?

 

[frv]

Look at Vulcraft's Tables for 1.5" Roof Deck. There are three different profiles. The economy of the profile will depend on where you live, but Type B seems to be the most popular where I live.

There is a specific section for rood deck.

Be aware that the values given in the diaphragm tables use Seismic factors of safety. You can get additional capacity from these decks by using the wind factors of safety, if you are in an area where seismic doesn't govern. You should look at SDI publications on the issue.

 

[JAE]

Light gage ROOFING usually doesn't possess diaphragm capacity. (unless it is specifically tested and advertised as such by the manufacturer)

Light gage DECKING does.

 

[frv]

JAE makes a good point- make sure you are aware of what they intend to use.

 

[msquared48]

The diaphragm rating of the decking depends on the manufacturer, and if it is rated. Contsact the manufacturer as mentioned above.

Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask

 

[asixth]

Agree with JAE. Corrugated metal roof sheeting cannot be considered a diaphram for the transfer of racking forces. If there is a manufacturers that is recommending that their roof sheet has diaphram capacity I would ask to see test certificates to say it has been tested and verified under accredited testing facilities. I wrote a post recently about using 0.42mm roof sheet (I think that converts to a 26 gage) as a diaphram and the consensus was NO.

thread507-270224

 

[hokie66]

The OP hasn't clarified if he is using steel roof decking or steel roofing. For all we know, he may be using decking and roofing above that.