So, they didn't nog out..

[cjard]

Interesting.. I was under the impression (from my builder) that the PB was fixed to the noggings at 2400..

No.

You don't see (plasterboard bonded joint) ceilings criss-crossed with noggs do you? .

Well, technically you're bang on! I'm a software engineer so the number of times I've seen an unfinished ceiling in my life is quite low

So, what centres do you fix your PB at?
And if it's anything less than the joist or stud centres, how do you get that fixing ratio at joins? Couple of YouTube videos I've seen thus far all have noggings and PB fixed to the noggings


Actually, I have another question arising from this for all of you who didn't nog the studs and hence didn't fix to the noggins, but haven't had any problems.. Were your free hanging joints a thick/rough edge or a tapered/smooth?

The other thing I suspect I might not have, is studs that are at 600mm centres. I'll have to get a measure on that and report back, but it may mean that I'm lying plasterboards long edge horizontal if I come across a 2350 wide panel.. Hmm

The other thing it may be prudent to mention.. I was thinking of tape and filling rather than full skim. Perhaps this makes nogging fixing more important, as the surface finish will be thinner at joints and less able to resist cracking

 

[freddiemercurystwin]

Bear in mind any scuffs or repairs in the future are harder to repair than a skimmed finish.

 

[shagster]

The plasterboard on timber frame provides fire resistance and needs to be fully supported. If joints are not fully supported, it may be difficult to prove that they will then provide the required 30 mins fire resistance, as the joint may open up in a fire.

I spoke to two BC officers, both of whom were perfectly happy with my garage ceiling arrangement, consisting of floor, 70mm celotex (continuous sheets), suspended timber battens below with 150mm screws going up through the celotex and finding the joists above. I got the advice of a structural engineer (who was helping me with some other work) to boot. The battens were at 400 centres with no nogs, and I think it would be pretty tricky to put them in anyhow. I put pink PB under the battens. Another option was two layers of the normal PB ovelapped, but that just seemed silly.

I mention this, because garages are one area that BC are pretty hot on (no pun intended). They told me I also needed pink PB over my garage walls adjoining to the house (that's double-skin with no cavity) in order to give 30 minutes fire resistance. I told them they've got to be kidding, and did they really think a 30 minute fire door would resist fire any longer than two layers of bricks. They later capitulated on that one. They also pointed out that one internal door was missing a third hinge, and that would be needed for fire regulations.

Why am I telling you this? Because I can't believe they would tell me all of the above, but neglect to mention that I needed nogs.

As an aside, when I asked about fire-rated back-boxes in TLC they told me they hardly ever sold them, so I suspect nobody cares that much about 30-minute fire resistance for stud walls. Perhaps it depends where the stud wall is?

 

[freddiemercurystwin]

In The White Book it's a recommendation I believe.

 

[freddiemercurystwin]

As opposed to to being a requirement that is.

 

[noseall]

The plasterboard on timber frame provides fire resistance and needs to be fully supported. If joints are not fully supported, it may be difficult to prove that they will then provide the required 30 mins fire resistance, as the joint may open up in a fire.

The cracking is just a decorative concern.

Whether or not building control will actually pick this up, or whether you want to do it 'properly'....the correct answer is to nog.

Show me a floor joist layout with a nogg pattern supporting ALL the plasterboard joints on plasterboard ceiling.

I have NEVER seen this done. Nor is it insisted upon by any governing body.

 

[cjard]

if the floor joists are at 600, 400 or 300 c/c, why is it not possible?

And if you've never seen a ceiling nogged, which is surely an area of higher flex and impact than a wall, then why are there others strongly proposing nogging the walls?

If noggins stop a wall's studs from twisting why aren't they fitted to floor joists? Items hung on walls would potentially induce the same kind of bending as a load on a floor..

I find the whole thing very inconsistent, which makes me think it's a crock

 

[RonnyRaygun]

If noggins stop a wall's studs from twisting why aren't they fitted to floor joists?

They are, or at least they should be. Noseall stated that he usually installs noggins at 1/2 or 1/3 span, depending on the joist length. That won't always line up with the end of the plasterboard. Cutting the plasterboard to line up with the position of the noggin would solve this but adds cost and wastage.

Items hung on walls would potentially induce the same kind of bending as a load on a floor...

Nothing like as much bending would be induced from a load hung on a wall. Unless there was a very long lever arm the vast majority of the load will be in shear.
The bigger issue with walls would be impact forces from potential collisions with the wall that could cause cracks to form at the joins. However, if the only joint is at 2.4m from the ground on a 2.6m high wall, this is unlikely to happen.

Noggins in walls do the same thing as in floors - they help to share the load between the main members and therefore increase the overall stiffness.

 

[AronSearle]

Show me a floor joist layout with a nogg pattern supporting ALL the plasterboard joints on plasterboard ceiling.

I have NEVER seen this done. Nor is it insisted upon by any governing body.

Show me test evidence that *1* layer of plasterboard without supported edges provides the required fire resistance.

You won't find it, you will just find manufacturers saying noggins are recommended where fire resistance is needed, as this is how their boards have been tested.

In The White Book it's a recommendation I believe.

Well yes, because the regulation is 'provide X fire resistance' you don't have to nog, you just need to demonstrate your construction provides X fire resistance.

Whether building control pass it or not has nothing to do with whether it works


What you do is up to you, and most times it won't be an issue, up to you what you do.

 

[noseall]

The plasterboard on timber frame provides fire resistance and needs to be fully supported. If joints are not fully supported, it may be difficult to prove that they will then provide the required 30 mins fire resistance, as the joint may open up in a fire.

The cracking is just a decorative concern.

Whether or not building control will actually pick this up, or whether you want to do it 'properly'....the correct answer is to nog.

How does a timber noggin supplement fire resistance?

 

[AronSearle]

Heat causes materials to expand/warp/ or otherwise react.

Noggins support the edges, if the edges are not supported, can you say they will not open up and allow fire through?

And before you call me a nutter, fire tests on plasterboard have been performance where using the wrong screws has caused the plasterboard to fail prematurely.

 

[noseall]

Heat causes materials to expand/warp/ or otherwise react.

Would the nogg not be a hindrance then?

 

[noseall]

Deleted, double post.

 

[noseall]

Heat causes materials to expand/warp/ or otherwise react.

Why are they not specified in conjunction with metal web floor joists?

 

[RonnyRaygun]

From NHBC Technical Manual: