Dry lining a solid walled bathroom - what to use?

[Craig]

Hello

We have rebuilt two storeys of our 4 storey extension. As we are building up from the existing wall top, the new brickwork wall is a solid 9" wall.

In order to comply with Part L, we are therefore going to insulate the inside walls.

We wanted to use a dot and dab thermal board with a pre-bonded plasterboard, such as Gyproc Thermaline Super. We are doing this (rather than using screwed metal/wood studs, etc. in order to save space as the rooms are tiny).

However, as these are all bathrooms, we need to find a final surface that is suitable for a damp environment.

British Gypsum has suggested bonding their green plasterboard (the moisture resistant board) to the Thermaline Super and then we can tile/paint this. However, our builder is concerned that this dab-fixed double thickness plaster board will not be stable enough for tiling/painting onto and will crack.

Has anybody got any relevant experiences they can share with me? I am surprised there is not a pre-insulated moisture resistant board available as I cant be the first person to insulate a solid walled bathroom!

Many thanks in advance for any advice,
Craig

 

[BMcD]

If you cross bond them ie 1st fix vertical, 2nd fix horizontal then they will be fine, probably stronger. If you plan to tile then try Wedi Board

http://www.wedi.co.uk/flash.php

 

[Craig]

Thanks. Both good sugegstions - the Wedi board looks perfect though. A thermally insulated tilebacker board. Will have to try to get a sample.

Gyproc came back and suggested using their Glasroc Soffitline - the plasterboard is impregnated with glassfibre to make it water resistant. Dont like the ide aof a glassfibre product though.

 

[Moneypit]

From the description of the Wedi board it also has glassfibre reinforcement. But don't be put off by that, what is your concern over its use?

 

[Craig]

Yes, just saw that. I guess nothing more than prejudice against horrible glassfibre wool stuff. If you have to drill it, is going to be bad for you?

 

[BMcD]

Just as a post script, if you use the moisture resistant board then it will need treating with a bonding agent if you plan to skim finish it any where

 

[Craig]

OK, thanks for that. Some areas will be painted so we were going to skim those.

We were looking at one solution that involved applying a sealer over a standard plasterboard to give the moisture resistant quality - but then the info said you cant tile over it!

 

[Craig]

Hmm - looks like the Wedi board may not have the a good enough U value. At 60mm of insulation, it has a U value of 0.61, and I think we need lower than that for works in an existing building?

 

[BMcD]

Try Marmox http://www.marmox.com/index.asp At 50mm there Uvalue is 0.54. Also Marmox can be plastered onto which I couldn't say for certain about Wedi board. I could see no mention of it on their spec.

 

[Craig]

Thank you. That looks even better. Will have a discussion with the architect about what we U value we are suppose to achieve.

 

[Essex]

You might find the Energy Saving Trust booklet CE184 Practical Refurbishment of solid walled houses useful

 

[Craig]

Very handy booklet - though some of the things it recommends are not "sympathetic" to older buildings!

 

[dragonfly]

Going slightly off topic, but not quite. I noticed yesterday that a tiny puddle has formed in our dining room directly under the shower tray. Tracking the source back, it looks as if the boxing around the shower pipes, and to which the shower taps are attached has started to warp, cracking the grout and letting water in. This is then running down the outside of the central heating pipes, which go straight own into the dining room. I think we are luck in that there is a little hole in the ceiling around the pipes which has never been filled as there is no detectable damp/ water staining on the ceiling around the pipe (which I guess would indicate pooling water). So would you suggest using this WEDI board stuff to rebox the shower pipes/taps. I am pretty sure it's just hardboard/ ply boxing at the moment. Don't need the soundproofing, just something waterproof, so if there are alternates, please let me know too.

Cheers

Dragonfly

 

[wobs]

How do these compare with Aquapanel?

 

[Craig]

The Aquapanel isnt insulated, but otherwise it would be suitable for that. You an also look at Hardibacker, especially where the tiles are very heavy.

 

[BMcD]

Dragonfly, I'm sure wedi board or similar would be ideal for your situation.

wobs wrote:

How do these compare with Aquapanel?

Since Aquapanel is a cement board, they are much lighter and as Craig says they are also insulated and come in various thicknesses