Noggins on mono-pitch roof?

[Jack07]

Hi,



Do I need to fit noggins between the rafters in my mono-pitched roof with a vaulted ceiling?

The span is 3m and I will be using 200mm joists to take the required 150mm insulation.



I was thinking noggins would get in the way of the insulation?



Thanks J

 

[robinbanks]

Are you thinking for prevention of twisting or for load transfer?

 

[SpecialK]

I didnt with a 3m span and 150mm rafters. I have 3 velux windows that add noggins.
Is 150mm the new regs? Do you have to overboard as well?

I also put some smaller noggins where lights and ceiling fans would hang from.

 

[Jack07]

My BO told me that the timbers need to be 175mm structurally BUT as the regs require 150mm insulation plus 50mm air gap I need 200mm joists. I was only putting in noggins for twisting.

If I can get away without then even better.

I will probably overboard with insulated plasterboard also for extra

 

[SpecialK]

My BO told me that the timbers need to be 175mm structurally BUT as the regs require 150mm insulation plus 50mm air gap I need 200mm joists. I was only putting in noggins for twisting.

If I can get away without then even better.

I will probably overboard with insulated plasterboard also for extra

What have building control said about the noggins? Mine was built before the changes. I over boarded with 40mm PIR. The more the better!

Dont forget the restraint straps either side. I had to add mine after!

I would also do the PIR that joins the wall end before doing that bit of the roof so you can make a good connection with the wall insulation.

Also mark the rafter positions on the walls so you can find them with the plasterboard screws...

 

[Mr Chibs]

I didn't put noggins in my vaulted ceiling 4.5m span, and also have Velux windows.
And it's signed off.

I had 100mm celotex in between rafters and 50mm below.
If doing the insulation separate to plasterboard, I found Wedi washers handy, to stop the screw heads pulling through the insulation/plasterboard.

 

[Jack07]

Building Control haven't been around yet. Need to set the rafters up first. Will ask when he comes around but wondered if people put them in. My roofer friend onmy said if I did then avoid fitting them flush with the tip of the rafter as it can trap the fabric and stop any water running down if it ever needed to.


Thanks for the tip on the wedi washers

 

[noseall]

Do I need to fit noggins between the rafters in my mono-pitched roof with a vaulted ceiling?

No. You do however need to fill out between the rafters where any restraint straps are fitted across, but this applies to the uppermost part of the rafter. Note the strap nogg's....

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[Dad'n'lad]

@noseall . Does that mean that I cannot have the 10mm sag on my membrane? Secondly, I can't find anything that shows the insulation in my cavity, joining my roof insulation to prevent cold bridging. Cheers.

 

[noseall]

@noseall . Does that mean that I cannot have the 10mm sag on my membrane? Secondly, I can't find anything that shows the insulation in my cavity, joining my roof insulation to prevent cold bridging. Cheers.

The sag thing is a trade-off in this instance, in that the felt is only expected to work if the the tiles fail.

Many (lazy) architects copy and paste cavity closing details onto their drawings without considering the heat loss issues at roof/wall abutments and how best to have a continuous run of insulation from wall to roof.

 

[John D v2.0]

The sag thing is a trade-off in this instance, in that the felt is only expected to work if the the tiles fail..

I thought it was also to direct any condensation coming off the back of the tiles to the gutter and the tiles thing was just a bonus?

 

[robinbanks]

But this is a warm roof construction; I don't think you'll see much condensation on the back of the tiles

 

[noseall]

I thought it was also to direct any condensation coming off the back of the tiles to the gutter and the tiles thing was just a bonus?

Yes. What I mean is the importance of the nog's overrides that of the condensation.

 

[John D v2.0]

Yes. What I mean is the importance of the nog's overrides that of the condensation.

fair enough point taken. If it was me I would use smaller noggings e.g. 6 by 2 on an 8 by 2 rafter just to be on the safe side. Could always rip them down to use up the offcuts.

 

[noseall]

fair enough point taken. If it was me I would use smaller noggings e.g. 6 by 2 on an 8 by 2 rafter just to be on the safe side. Could always rip them down to use up the offcuts.

We always locate them high enough out of the way so that they don't clash with the (vaulted roof) insulation.