Plasterboard ceiling warped Victorian joists with Gyproc 4TE

[nishnish]

Hi,
I've pulled down a plaster and lath ceiling in a Victorian house (1890) as parts of it were coming away.

Sorry, that this is so long, but I thought extra detail would be useful.

I want to plasterboard it, but some of the joists are slightly different levels, only about 5mm out vertically. They are pretty bob on horizontally in both dimensions.
However, the spacing varies quite a bit and one joist (2nd from a wall) is warped. It looks from the mountings of that joist, which are fine, that the joist was warped when the Victorians installed it. Cheapskates
The room is 3.85m*3.12m with a chimney breast, which has a constructional hearth supported in the joists above. It's a 1st floor room, with 2nd floor room above.
I wondered what would be the best way to plasterboard this?
Install a new batten framework, screwed to the joists, with relevant packing to get it level?
Or is it possible to noggin the joists? Possibly a tedious job?
If battening, what would be a good size for the framework? As it's attached to existing joists, I'd expect the framework could be relatively light, relying on the existing joists for support i.e. as small as 1"x1" or would a greater dimension of battens be needed? I'd like to keep the depth to a minimum to maintain ceiling height. It's 2.85m high, but I don't wanna waste space unnecessarily. Would; 1" depth x 2" width; be better to provide decent (wider) fixings for boards, and/or is 1" depth just too lightweight?
The joists are actually in pretty good condition, apart from exceptions above. They vary but are 55-65mmX165-175mm.
I've not done anything like this before, but think it within my skill range.
I'd like to use tapered boards, as I fancy DIYing all of it. If the finish is unsatisfactory, I'll get it skimmed at some point in the future, but currently finish is not paramount.
I was interested in the Gyproc 4TE boards which are tapered on all four sides. Because I'd like to avoid the problem of the butted square ends I'd inevitably get on a ceiling which is over available board sizes; 2.4m or even 3m.
Are these boards available for a reasonable price. They seem to have pretty limited availability.
Do other manufacturers produce a 4 tapered edge board? I could only find the Gyproc product.
Thanks for any advice you could provide.

 

[ajrobb]

I was told by an SE that a single layer of plasterboard would be much noisier than the original lathe and plaster. You could use two layers of plasterboard on resilient bars. They isolate vibration but might take up some of the variation. For best results, you can use Soundboc plasterboard and 100mm of acoustic mineral wool.

 

[2929twin]

If all you want to acheive is a flat ceiling, run a string line across, under all of the joists, adjusting down with shims under the 2 ends untill just touching the lowest joists.(You could us a long straight edge but more awkward) Measure the gaps between string and joist, rip some 4x2 or 6x2 whatever down to the measured sizes eg. 50mm x 5mm then pin them to under joists.
I wouldn`t worry about less than 2 mm you wont see it. Then just nail up the new boards.
You have to join board ends on joist for support, so you`d be very lucky to find a vicy house with timber at the exact centres to match board lengths.
Any way aren`t vicy houses suposed to have lumps and bumps as character?

 

[nishnish]

I was told by an SE that a single layer of plasterboard would be much noisier than the original lathe and plaster. You could use two layers of plasterboard on

Always the way. Even with someone who purports to give lots of info and says sorry about it, that they neglect to mention something

We bought it in Nov and we're surprised by how noise travelled through the house. I planned to put acoustic board everywhere, it's needed, to at least have a go at alleviating that. Can't do any harm and not that much more cost wise. As 4TE has not the same sound blocking properties, I thought of using two layers; acoustic board (SoundBloc whatever) and then 4TE to make the finishing easier.

I did plan to use the acoustic board to provide the density to alleviate certain aspects of the noise and then some kind of rockwool (as you mention) to help with the higher frequencies. One advantage of pulling down the plaster and lath is that all that crap between the floorboards/joists is gone. Nice clean area to work on. Perhaps all that dust/crap was helping deaden the sound Tho it was surprisingly noisy, so I think it's possible to do better?

I think I rambled. I was more concerned about how to make a strong, crack resistant & level ceiling i.e. supporting the PB properly.

 

[nishnish]

Measure the gaps between string and joist, rip some 4x2 or 6x2 whatever down to the measured sizes eg. 50mm x 5mm then pin them to under joists.
I wouldn`t worry about less than 2 mm you wont see it. Then just nail up the new boards.

Ok. Even tho I don't wanna lose too much height, that does sound more fiddly than just running battens of a suitable strength all over. But it was me that said I didn't want to lose height. Thanks for the detail

You have to join board ends on joist for support, so you`d be very lucky to find a vicy house with timber at the exact centres to match board lengths.

Yeah, that's why I thought I might need to batten. Noggins or shims to adjust what I've got to provide support to board edges would a royal pain.
I was thinking that the current joists have no chance of being on board edge, even with shims. I would have to essentially create my own new joists (board fixings) on board edge, with noggins perpendicular to the joists, which seems a lot of work. Or lay thin (as possible) battens across to make perfectly spaced new supports for the boards.

Any way aren`t vicy houses suposed to have lumps and bumps as character?

Ah. Now this part sounds like what me missus said
I wanted to do one room the difficult (more time consuming) way. Pull down the plaster and lath and board a modern 'perfect' ceiling.
As I said, I've not done anything like this before, so thought I'd experiment on this room.
It's kind of a spare room. We have others to do. Considering the toil involved there, we'd take those ideas on, or adjust the plan for the other problem areas.

 

[ajrobb]

With battens or resilient bars running across the joists, you can space them at exactly 400mm so you have to cut fewer boards. With 2 layers, the minimum overlap should be 600mm so the joints are properly supported. (You also get 60 minutes fire resistant ceiling rather than 30.)

 

[nishnish]

With battens or resilient bars running across the joists, you can space them at exactly 400mm so you have to cut fewer boards. With 2 layers, the minimum overlap should be 600mm so the joints are properly supported. (You also get 60 minutes fire resistant ceiling rather than 30.)

I wasn't planning to go so far as resilient bars. Or do they have some other advantage over battens? Easier to work with?
Supposing battens, what dimensions would be sufficient for this ceiling?
The sheds only seem to go up to 3.6m. I take it one length per span is a much better idea?
Thanks.

 

[ajrobb]

do they have some other advantage over battens?

Being resilient, I thought they might take up some of the height variation.

Oh and as there is a 2nd floor room above, you might want to support the insulation on non-flammable chicken wire to improve the fire resistance. Have a word with your LABC, they can advise you better on safety.

 

[nishnish]

Being resilient, I thought they might take up some of the height variation.

Resilient channel/bar is certainly seeming more appealing.
It provides this extra decoupling, but also doesn't too hard to work with and seems cheaper than wood, at least here:

http://www.sigexpress.co.uk/Product...ress&utm_medium=Froogle&utm_campaign=Shopping

It seems that you only need to lay the resilient bars across the joists. So the long edge of the PB, will only be supported every 400mm. Won't that be an issue? When you do this with wood, isn't it normal for all edges of the PB to be supported by a batten?

Oh and as there is a 2nd floor room above, you might want to support the insulation on non-flammable chicken wire to improve the fire resistance. Have a word with your LABC, they can advise you better on safety.

Good idea. Tho I did plan to use metal for that.
Is this work notifiable? <sigh>

 

[2929twin]

This simple fix for getting a flat ceiling is getting a bit intense.
First posting never mentioned fire rating or sound proofing.
However the resilient bar system is to be screwed at every joist crossing, so you still have to pack down to a level or at least straight run. otherwise the bar will deflect and stress the profile thus reducing the effectiveness of the bar, with the boards screwed to.
The bar system is a air transmitted sound reducing method, it doesn`t do much to address the more common impact noise ( foot steps etc)
We used this on an apartment renovation. The full system includes, resilient bar, 100mm insulation between joists steel capping strips on rubber on top of joists and strips of sound block in these cappings. Chip board floor over and sound deadening underlay before carpets.
We`ve kinda gone away from the `just a flat ceiling` idea fellas, but in for a penny in for many pounds.

 

[nishnish]

This simple fix for getting a flat ceiling is getting a bit intense.
First posting never mentioned fire rating or sound proofing.

That's right. Nothing wrong with suggesting it tho? I appreciated it at least.

The bar system is a air transmitted sound reducing method, it doesn`t do much to address the more common impact noise ( foot steps etc)

I appreciate that, but as both floors are the same property, I'm not that bothered by that. Reduction of conversation, TV, music, etc. would be fine.

We used this on an apartment renovation. The full system includes, resilient bar, 100mm insulation between joists steel capping strips on rubber on top of joists and strips of sound block in these cappings. Chip board floor over and sound deadening underlay before carpets.

Thanks for that, very interesting.

We`ve kinda gone away from the `just a flat ceiling` idea fellas, but in for a penny in for many pounds.

Indeed. I asked what size battens I would need and got much more detail which is greatly appreciated.
Thanks guys.

 

[ajrobb]

It seems that you only need to lay the resilient bars across the joists. So the long edge of the PB, will only be supported every 400mm. Won't that be an issue? When you do this with wood, isn't it normal for all edges of the PB to be supported by a batten?

I don't think ordinary PB ceilings support the long edges. Maybe that is more important for walls. However, resilient bars always seem to be used with 2 layers of PB with staggered joints, so the edges are supported.

It's not like you are after the ultimate noise insulation. I'd try just ordinary PB rather than the more expensive Soundbloc.

Is this work notifiable? <sigh>

I doubt it is notifiable, it's not like you are making significant changes. It is just that LABC will give you information about how to bring the building up towards modern safety levels. As long as you don't do anything to make things worse, they can't force you to make improvements.

 

[nishnish]

I don't think ordinary PB ceilings support the long edges. Maybe that is more important for walls. However, resilient bars always seem to be used with 2 layers of PB with staggered joints, so the edges are supported.

Ah. Of course. The boards will support each. Didn't think of that.

It's not like you are after the ultimate noise insulation. I'd try just ordinary PB rather than the more expensive Soundbloc.

Yeah, I was coming round to that opinion too.

Is this work notifiable? <sigh>

I doubt it is notifiable

Ok. That's a relief. Just starting out on this kinda thing.
So much to learn
This thread has helped. I had read about resilient bars, but had ruled them out as only for home cinema, conversions, etc. But come to think of it, as I said, we do have a noise issue, so I'd like to try it.

I'm still concerned about the finish on the butted together square edges. I wanted to avoid getting a plasterer in, at least initially. The Gyproc 4TE seems attractive because of that. Though it seems hard to get hold of. That makes me think it's not really necessary for a 3.85mx3.15m room.
Or am I just worrying about something that will look good enough?

 

[ajrobb]

Have a look at the British Gypsum Site Book for instructions.

I've been reading around a bit and the following is my novice understanding in brief:

In the USA and Canada, a plaster skim is rarely used. Self-adhesive webbing jointing tape is probably easier to use but paper tape is supposed to be stronger. Follow the instructions on the Easifill bag. Apply a dry lining primer with a roller to give a slight but uniform texture. (Primers come in a range of greys to match the top coat for one-coat cover.)

 

[nishnish]

Have a look at the British Gypsum Site Book for instructions.

It says use tapered edges for a 'seamless surface ready for decoration'. Though it shows tapered boards the full height of a wall i.e. no butted square ends. That implies that square edged boards aren't seamless. Well yeah we knew that, that's why we wanted tapered edge in the first place
They do make 3m and 3.6m boards which would handle my 2.85m walls and also the ceiling span of smaller rooms. However, they are harder to find and I'd expect hanrer to handle. That probably prohibits them. Which means being left with 2.4x1.2 boards, with butted square ends where they don't form a complete span.
I guess what I'm asking, in a very circuitous way , is even when using tapered edge boards, will the butted square ends be that noticable?