Fixing Noggins & Plasterboard to Roof Trusses

[roarsa]

We have a garage that has a trussed roof that I want to install a plasterboard ceiling. We have to double board it to meet Building Control approval. To allow edges of the plasterboard to be supported I need to add noggins between the roof trusses, (trusses are at 500mm spacing).

Am I allowed to screw through a truss chord to fix noggins, and am I ok to screw plasterboard directly to them?

I always believed that you can’t notch, drill, screw or nail through a roof truss, not even the lower chord as it’s structural.

 

[23vc]

Why does it need to be double boarded?
Why do you need to add noggins?
Yes you can obviously screw into a roof truss.

 

[^woody^]

On houses with trussed roofs, how do you think they plasterboard the bedroom ceilings?

 

[roarsa]

...

 

[23vc]

?

 

[roarsa]

Why does it need to be double boarded?
Why do you need to add noggins?
Yes you can obviously screw into a roof truss.

thanks 23vc. The building control guy that came out said he wanted me to double board using 9mm plasterboard to meet the fire rating. The trusses are 500mm apart and at that spacing I’ve been told that the plasterboard risks sagging without me adding noggins to support the bound edges and also down the middle of each board.
Do you think I’m over engineering?

 

[roarsa]

On houses with trussed roofs, how do you think they plasterboard the bedroom ceilings?

I don’t know whether house trusses are specifically designed for noggins, or whether the noggins are fixed in a specific way.

 

[23vc]

Why do you need to fire protect a non inhabitable roof space?
500mm joist centres don’t need additional noggins unless you’ve got a big space at the edge

 

[^woody^]

You don't need to double board a garage ceiling unless there is a habitable room above. Double boarding is more for smoke and fumes not fire, as 12.5mm board and skim gives the required 30 minutes fire resistance - just like every other ceiling in the house.

 

[roarsa]

Why do you need to fire protect a non inhabitable roof space?
500mm joist centres don’t need additional noggins unless you’ve got a big space at the edge

thanks again 23cv.
The backstory is:
This is currently a garage that we’re converting the rear half into a studio type room, retaining front half as garage type storage. We’ve gone through Building Control as we may need this to be classed as a proper habitable space later due to some health issues that may need we need an easy to access room.
Building Control want more than we’d originally intended, such as tons of kingspan to insulate the external walls etc and also needing to create a fire box by double plasterboard on the ceiling.

Thanks for the advice on the need for noggins. I’d heard that 9mm plasterboard sags without them, but it’s a job I could do without.

 

[roarsa]

Why do you need to fire protect a non inhabitable roof space?

Just re-read your comment. No habitable room in the roof space, no. Hmm looks like the BC guy is asking for more than is needed.

 

[roarsa]

You don't need to double board a garage ceiling unless there is a habitable room above. Double boarding is more for smoke and fumes not fire, as 12.5mm board and skim gives the required 30 minutes fire resistance - just like every other ceiling in the house.

thanks. Looks like I’ve a BC guy that is asking for more than is required then. I’ll phone and talk to him to ask him to either reconsider or explain why he expects double layer.

 

[23vc]

Forget 9mm board, use 12.5

 

[roarsa]

Forget 9mm board, use 12.5

Thanks. I’ll do that.