Jump to content

Suspended Ceiling under a flat roof : how best?


ToughButterCup

Recommended Posts

I need to install a suspended (dropped, false)  ceiling under a flat roof.

 

The primary aim,  is to provide a carrier for  a vapour barrier and 25mm of insulation under our POSI joists.

 

At the same time, I'd like to create a generous service gap to carry water, electricity cable,  MVHR piping and I suspect there'll be a bit of data cabling too. 

 

The span to bridge is less than 2 meters. The load on top of the joists is very small : just some insulation and a waterproof membrane. I have checked with the joist manufacturers and they say that what I propose is well within the design limits, and the BCO, when told, didn't even bat an eyelid.

 

I've read these posts;

 

The POSI designer sucked his teeth a bit when I talked about screwing stuff to the bottom of the joists: I explained that SWMBO had vetoed me suspending my engine hoist from the joists.... 

 

My instinct is to KISS

  • 3 by 2 wallplates
  • 2 by 2 cross-pieces
  • vapour barrier
  • batten the 25mm insulation (under the vapour barrier) to the 2 by 2 cross-pieces
  • plasterboard
  • skim

OR

  • Screw some sort of simple support system to the bottom chord of the POSIs  

 

I'm at the ' its keeping me awake at night stage '   Help me untangle my brain about this one please!

Link to comment
Share on other sites

What do you really want to achieve? 

 

More specifically if you don't drop the ceiling at least the diameter of your mvhr pipes you are going to have penetrations in it. Technically it would be that diameter +25mm so you don't need to channel the celotex. 

 

Just to throw it out there. Why not utilise the fact you have posi joists. Run everything in the joist space. (through ducts will make sealing the penetrations easier) 

 

Then insulate. Vcl. 25mm batten and screw up into the posis. 

 

25mm is plenty of space for flat panel down lights and associated cables. Nice short screws. 

 

Done. Onto the next job ?

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
×
×
  • Create New...