Surfacing an old wall

[Jackie]

I have got a real rough old wall that I want to tile. The basic wall is stone blocks but someone has in the past thrown concrete at it and this has resulted in a wall which is lumpy bumpy. The surface seems quite sound however. I want to have a smooth surface and I had thought to fix vertical battens at just over one metre intervals and then fix boards across one at a time and starting at the bottom. After fitting each board ramming in a 3 to 1 mix of sand/cement. In this way casting a new surface for the wall working upwards. The wall is not really bearing much of a load and other walls in this area are breeze block again with lumps of concrete thrown at them which are on tight. I would wet the wall down before casting. The thickness of the coating will vary between one and five centimetres. This seems to be a quicker idea than rendering in layers. The boards would be thick enough to prevent bowing. Any comments folks or is this a no no? ..........................John in Dept 79

[Dave&Olive]

dry line it ......if I got the question right..

[Nick Trollope]

[quote]dry line it ......if I got the question right..[/quote]

Exactly - why not use the boards to hold up the tiles? Or better still green plasterboard.

Have we both misunderstood?!

[Jackie]

Thanks for the replies. Well I guess there is no real reason why I should not use plasterboard other than losing several cms of space in front of each wall. I have used plasterboard on both metallic rail and wooden frame in the past and then tiled with success. I just thought it would make a change to do it this way and would give a stronger job. As I would do this in sections I would not need that many boards, I already have a collection from a previous job, and would only cast about a third of the wall height each day. Plenty of other jobs to do whilst waiting for the concrete to harden.

I gather concrete is a good surface on which to lay tiles. These are mostly internal walls and not damp but I would use an exterior grade adhesive anyway. I can see that the rail and plaster board method would protect the tiles against slight wall movement but I don't think that it is going to move as the only weight on it is the metal and plastic veranda roof. I guess I was just curious to know if there was any good reason why I should not do it this way. I would have thought hydrofuge plaster board and metallic rail would be actually more expensive than concrete. Any further thoughts folks?.........................John in Dept 79

[cabman]

I agree with previous replies, dry lining is probably favourite, but more expensive.

As space is at a premium, have you considered chipping the offending concrete off and re-rendering? Can you hire a Kango in France? I would have thought once started, concrete would part from the old limestone with a conventional cold chisel.

I feel trying to ram concrete into a 1cm gap behind board would be slow, difficult and impossible not to create voids.

[Piprob]

I would personally dry-line. But the principle 'concern' with the way you want to approach the job is damp, and that's probably a somewhat theoretical consideration in your case - so your method may be worth a try.

Use of tiling suggests the room is going to be subject to condensation. You can suppose the grouting will prevent damp from travelling through to the wall surface. However, if it does find a way in, it might eventually reach the original wall surface, moving faster this time by capillary action where the surfaces meet. Eventually this would loosen the bond between the surfaces, but it might take a long time to do so!

 

[Michael]

John why not use 22mm thick marine ply on the wall and increase the u value at the same time.Unibond the wall and ply and screw it straight on,saves all the work on studding plus a first class surface for tileing and screwing sanitary items to.

[Jackie]

Well thanks for all the suggestions folks. I have decided to try casting the surface of the shortest wall. I have added one modification and that is to screw a rusty iron grid, as used for reinforcing concrete, had some left over from another job, to the wall first. I will see how this goes and consider other options suggested for the other, larger walls. Again many thanks and all the best.............John in Dept 79