Clive wrote:
Hi,

When I convert a room into bathroom (and get planning permission -
thanks for note) I want to insulate the walls. The house is a
Victorian brick-built end-of-terrace and the two external walls are
absolutely freezing (although we *are* in the Hertfordshire polar
winter currently).

As I understand I have two insulation options:

1. External insulation

2. Internal insulation

I don't want external cladding on my lovely two-tone Victorian
brickwork.

So I need internal insulation. One wall can be dry-lined, insulated
and plasterboarded as the room is big enough to take this loss of
depth. However, the other external wall "abutts" the door frame and
there is a 2cm "return" before the door frame on the internal wall.
So, another drylined wall is out of the question - because I wouldn't
be able to open the door.

If I use polystyrene sheets against the wall underneath ceramic
tiles

3. Would this setup this result in any thermal insulation benefit?

I think every little helps, especially in reducing condensation.

4. Would this polystyrene surface be strong enough to support tiles or
will the weight of the tiles pull the polystyrene away from the
underlying plaster?

I wouldn't put ceramic tiles over polystyrene. They would probably stick
quite well but any little knock could crack the tile.

5. If I had the plaster hacked off right back to the brick, could I
get enough depth to usefully dryline and insulate this wall?

In my house you'd gain about 15mm that way.

Have you thought about tile panels? Not a great choice of designs, but
only 3mm thick and most of that is the polystyrene backing.

http://www.neken.co.uk/