Repairing a lath & plaster ceiling.

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Repairing a lath & plaster ceiling.
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Slim

Joined: 05 Mar 2006
Posts: 6612
Location: New England (In the US of A)

Posted: Thu Sep 07, 17 12:20 pm Post subject:

Will the other walls ever be opened up in the future? Piecemeal can be okay for refurbishing....

What is celotex made out of? Will it be okay if moisture makes it in? I would think modern rockwool would be appropriate....

The bathroom exterior walls are where I would expect you'd most likely find humidity condensing within the wall. A bit of insulation may help to reduce that, but I know that these things quickly get tricky balancing a desire for breathability to dry things out and moisture barriers to keep humidity on one side or another.....

Hairyloon

Joined: 20 Nov 2008
Posts: 15425
Location: Today I are mostly being in Yorkshire.

Posted: Thu Sep 07, 17 1:38 pm Post subject:

Slim wrote:

Will the other walls ever be opened up in the future?

Probably not.

Quote:

What is celotex made out of? Will it be okay if moisture makes it in? I would think modern rockwool would be appropriate....

Polyisocyanurate. As I understand, this is a standard way of doing this kind of thing...

Quote:

I know that these things quickly get tricky balancing a desire for breathability to dry things out and moisture barriers to keep humidity on one side or another.....

I couldn't begin to guess which side would be which. I decided to not worry about it.

dpack

Joined: 02 Jul 2005
Posts: 46235
Location: yes

Posted: Thu Sep 07, 17 1:54 pm Post subject:
as above re damp issues etc as shown recently in london the stuff burns and if it does a breifcase sized lump produces enough one lungful toxic gas ( mostly hcn but a few other choice compounds ) to need a noddy suit in a large house on the outside is potentially dodgy, inside why not use rockwool slab

Hairyloon

Joined: 20 Nov 2008
Posts: 15425
Location: Today I are mostly being in Yorkshire.

Posted: Thu Sep 07, 17 3:14 pm Post subject:
Still leaves the question of whether to use anything...

dpack

Joined: 02 Jul 2005
Posts: 46235
Location: yes

Posted: Thu Sep 07, 17 11:09 pm Post subject:

improving ventilation is my best advice for condensation damp

re insulating a cold wall where water vapour condenses a simple skin of suitable boards over rockwool slabs or mineral panels with suitably sized battens will make the inner surface a lot warmer and less prone to "dew "

it does make the room a bit smaller which can be an issue especially if you have to move the bathroom suite in a bit

Hairyloon

Joined: 20 Nov 2008
Posts: 15425
Location: Today I are mostly being in Yorkshire.

Posted: Thu Sep 07, 17 11:28 pm Post subject:

dpack wrote:

improving ventilation is my best advice for condensation damp

That wasn't actually the problem that we seek to address.

Quote:

it does make the room a bit smaller which can be an issue especially if you have to move the bathroom suite in a bit

The suite is coming out anyway and the room is big enough that it can spare a few inches off the end.

dpack

Joined: 02 Jul 2005
Posts: 46235
Location: yes

Posted: Thu Sep 07, 17 11:51 pm Post subject:
if chilly is the issue extra insulation ain't as good as a holistic approach when retrofitting houses but good heating, good ventilation and good insulation can make a home cosy "it always feels quite chilly" in a room often has a damp component

Hairyloon

Joined: 20 Nov 2008
Posts: 15425
Location: Today I are mostly being in Yorkshire.

Posted: Fri Sep 08, 17 12:23 am Post subject:

dpack wrote:

if chilly is the issue extra insulation ain't as good as a holistic approach...

I don't recall any complaints about chilliness. The plasterboard was deemed the easiest route to something to put tiles on.
The insulation is very much just a case of "why not?"

Slim

Joined: 05 Mar 2006
Posts: 6612
Location: New England (In the US of A)

Posted: Fri Sep 08, 17 11:22 am Post subject:
Whoa, tiles going on gypsum board and not on cement board? That's the way it used to be done here, but not for a long time. If it's worth tiling, it's worth backing with cement board. (I believe that's the present thinking)

dpack

Joined: 02 Jul 2005
Posts: 46235
Location: yes

Posted: Fri Sep 08, 17 5:46 pm Post subject:
yep, waterproof board is sensible, cement based, waterproof mdf or marine ply are suitable behind tiles

Hairyloon

Joined: 20 Nov 2008
Posts: 15425
Location: Today I are mostly being in Yorkshire.

Posted: Fri Sep 08, 17 9:13 pm Post subject:

dpack wrote:

yep, waterproof board is sensible,

cement based, waterproof mdf or marine ply are suitable behind tiles

You don't rate the moisture resistant plasterboards?

Slim

Joined: 05 Mar 2006
Posts: 6612
Location: New England (In the US of A)

Posted: Fri Sep 08, 17 10:10 pm Post subject:
I've heard that those can be okay for areas that you don't expect to get wet, but that they're still not the best choice

dpack

Joined: 02 Jul 2005
Posts: 46235
Location: yes

Posted: Sat Sep 09, 17 10:49 am Post subject:

moisture resistant is ok for kitchen/bathroom walls/ceilings etc but if it is a "wet" area ie it needs tiles it is best to use a properly waterproof substrate board.

for tiles it needs to be ridged as well so good battening (pre treated with preservative ) and a thick enough board combo is best.

the trickiest bit is getting the front face of the battens shimmed out to a flat surface to take the back of the boards. a long bubble/long strait edge and chalksnap plumbline are handy to set the edge battens and then to work in from the edges making sure everything fits tight to the plane of the boards using the strait edge.

any mistakes at that stage will cause issues later

Hairyloon

Joined: 20 Nov 2008
Posts: 15425
Location: Today I are mostly being in Yorkshire.

Posted: Sat Sep 09, 17 8:31 pm Post subject:

dpack wrote:

moisture resistant is ok for kitchen/bathroom walls/ceilings etc but if it is a "wet" area ie it needs tiles it is best to use a properly waterproof substrate board.

I'd instinctively agree, but I've just part-dismantled the old shower cabinet and it seems to have been made of ordinary gyproc plasterboard, tiled over: doesn't seem any the worse for wear from being the back of a shower for many years.

dpack

Joined: 02 Jul 2005
Posts: 46235
Location: yes

Posted: Sat Sep 09, 17 10:29 pm Post subject:
sometimes it is ok, if all the plumbing,tiling,grout and sealing is perfect to start and repaired as required and the house does not move causing even a small hole somewhere important it can be ok. i have put a lot of horrible black messes in skips though and always try to use waterproof substrates if any tiling will ever get wetter than a damp cloth

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