Converting toilet/WC to shower room

[jasonj]

Hi

I have an old Victorian (circa 100 years old) property which has a downstairs bathroom at the back, which itself has a doorway to a smallish toilet room/WC (that I suspect may originally have been an outside toilet; I don't know). We have resited the toilet to inside the bathroom and are in the process of converting the space freed up into a shower room.
The existing brickwork is only single skin so I need to build a second skin, which I am doing with low density blockwork (the stuff that you can cut with a saw). The problem is that there is not going to be much or any of a cavity between the two skins. I believe the cavity is supposed to provide two functions - one is a thermal barrier (but perhaps only if filled with something) and two is moisture barrier?

Questions I have are:

1 Given that I don't have enough space to play with to allow me to fit something like Celotex, is there anything I can do given that the cavity (such that it is) will be only a few mm wide?
2 Can I (or should I) put some damp proof membrane between the two skins, and if so how would I 'fix' it in place?

By the way, the shower will be ventilated with a fan which vents through the roof which comes on when the light is switched on. Also there will be a fan in the bathroom. Oh, and I have already bought Aquapanel for the plasterboard duties for the wall and ceiling.

Thanks.

 

[mointainwalker]

What thickness of blocks are you planning to use ?

 

[jasonj]

Standard thickness (the ones you get in Wickes; the thickness of a standard house brick which I guess is something like 100mm?).

 

[mointainwalker]

Well, why not make it a stud wall using either wooden battens or steel rails and uprights ( the latter are 45 mm deep )

You could then put the insulation thickness of your choice between the studs and still leave a cavity to the outside wall.

The insulation values of any of the usual materials ( not multifoils ) are 3 to 4 times better than these blocks for same thickness..

 

[jasonj]

That's a good idea, not one I had thought of. Unfortunately I already have the breeze blocks, although I could take them back.
I am reading up now on how to construct a stud wall.
I take it then that it is acceptable to construct the inner skin of an external wall as a stud wall?
Also, the shower 'room' doesn't have a ceiling into which to nail or fix the head plates for the stud partitions (it is pitched and currently you can see the rafters in the 'roof'); how then would I get around that?

Thanks.