MF ceiling - how many MF7 "primary support channels"?

[theflyingpig]

My room is approx 5 metres by 3.2. My plan is to run the mf7s along the 5m length, then the mf5s across the shorter length at 450mm centres. .....
I don't seem to be able to establish how many runs of mf7s are reccomended.... Is two enough of they're strapped up to old joists?

Thanks!

 

[freddiemercurystwin]

Maximum 1200 centres.

 

[theflyingpig]

Tha

Maximum 1200 centres.

Thanks, but does that include using the perimeter as a fixing point? So if room is 3200 wide, I'd just need two?

 

[freddiemercurystwin]

Yes, an MF6 all around the perimeter and then 2 No MF7's at 1066mm centres.

https://www.british-gypsum.com/documents/white-book/british-gypsum-wb-gypceiling-mf.pdf diagrams 1 & 2 on page 4.

 

[theflyingpig]

Great, thanks!