Levelling wall for tiling

[zand108]

I am retiling my bathroom with large 25mm x 40mm tiles laid horizontally (bricklike). From the sticky in the tiling forum I understand that for large tiles the surface needs to be as flat as possible.

However one of my walls is slightly concave. The majority of the wall is only out by ~2-3mm both horizontally and vertically however towards the centre of the wall this sharply increases to 6mm horizontally and 4mm vertically out of line.

Is the unevenness of this wall likely to pose a problem when laying my tiles?

If yes, There is not enough space to dot & dab plasterboard as the bathtub sits in an alcove created by this wall and two others which is pretty much the size of the bathtub.

So presumably I would need to float the wall flat with plaster, timber grounds and a featheredge but I am unsure which type of plaster to use for this job either:

Single coat of Bonding Coat or
Several coats of Multi-Finish

or what size grounds to use having skimmed but never floated a wall before?

As the majority of the wall is only 2mm out of line would Bonding Coat be appropriate I have read that applying Bonding Coat thinner than ~5mm can create an unstable background for the finish coat.

Many Thanks.

 

[roy c]

Why dont you spread the wall out from the highest point with tile adhesive? Then vary the depth of adhesive on the next coat to compensate??

 

[roughcaster]

You're up late tonight Roy.

Roughcaster.

 

[roy c]

Hi RC how you doin?

Yes I have had my mate around fixing our main computor. Have been on the lap-top now for a few months, he has sorted the main one out , I am just waiting for it to finish down loading all the "Bumph " he has put on it!!! Am up in Prestwick for Christmas so make sure we get "mild " weather eh???

 

[zand108]

Why don't you spread the wall out from the highest point with tile adhesive? Then vary the depth of adhesive on the next coat to compensate??

Hi Roy C thanks for responding.

I have never tiled a wall before so I don't know how easy or not it is to compensate for an uneven wall with tile adhesive.

But are you suggesting that I should build out the tile adhesive to the required level by allowing it to dry between coats?

 

[roy c]

Why not? 4-6 mm is'nt to bad just feather it out on the low spots and when you tile use quite a good knotched trowel and then when press your tiles on you can vary the pressure you put on them to bed them in....I'm a plasterer so feathering in and building out is as easy with tile adhesive to me as skimming it...But if you bond or skim it you will have to wait a while longer before you can tile on it...

 

[Richard C]

4mm over a 2.2m floor to ceiling height is nothing & even 6mm is manageable if it’s over around 1m or so. Just fill & feather a layer of adhesive before you tile as suggested but use a waterproof, cement based powder adhesive (BAL) not redimix. I recently finished an en-suite using 600 x 300mm tiles in a large shower enclosure & the back wall was convex around 5mm each side of a 900mm wide enclosure; didn’t have any problems & it looks perfect.

 

[gday2uk]

I am retiling my bathroom with large 25mm x 40mm tiles

They're not very big

 

[Richard C]

I am retiling my bathroom with large 25mm x 40mm tiles

They're not very big

 

[zand108]

Thanks to everyone that has contributed. I really appreciate it .

I am installing a shower and so want to Tank the walls before I tile over them. Would the following sequence be acceptable.

1. Tank the wall.

2. Fill & Feather the entire wall to make level with "powdered" waterproof wall tile adhesive then allow it to dry.

3. Tile over "levelled wall" making adjustments with pressure & extra adhesive (if necessary) as I go along.

Also as an aside if I were to feather with plaster for such small depths would you recommended using Bonding Coat or Multi-Finish?

Many thanks again!!

 

[Richard C]

I am installing a shower and so want to Tank the walls before I tile over them. Would the following sequence be acceptable.

1. Tank the wall.

2. Fill & Feather the entire wall to make level with "powdered" waterproof wall tile adhesive then allow it to dry.

3. Tile over "levelled wall" making adjustments with pressure & extra adhesive (if necessary) as I go along.

Sounds OK; are the walls plaster board or plaster over block? I would normally only tank plasterboard but I always use a tile backer board in such locations & I don’t tank that before tiling!

Also as an aside if I were to feather with plaster for such small depths would you recommended using Bonding Coat or Multi-Finish?

You could use either if tiling over it but you if using Multifinish, build it up in 2 coats if the difference is more than around 3/4mm or there is a very good chance it will craze. Bonding is good for around 10mm in one hit.

 

[zand108]

Sounds OK; are the walls plaster board or plaster over block? I would normally only tank plasterboard but I always use a tile backer board in such locations & I don’t tank that before tiling!

The walls to be tanked are a combination of plasterboard and plaster over brick.

I am installing an over the bath power shower where the spray will be directed onto the "plaster over brick" wall so I thought it would be prudent to tank that wall.

I have read that applying Bonding Coat thinner than ~5mm can create an unstable background for the finish coat.

Was I mistaken in thinking that filling & feathering out with bonding coat and spreading it out to depths less than 5mm (or as in the majority of my case ~2mm) can leave a finished surface which is soft & "crumbly" and unsuitable for skimming onto?

 

[Richard C]

I have read that applying Bonding Coat thinner than ~5mm can create an unstable background for the finish coat. Was I mistaken in thinking that filling & feathering out with bonding coat and spreading it out to depths less than 5mm (or as in the majority of my case ~2mm) can leave a finished surface which is soft & "crumbly" and unsuitable for skimming onto?

Are you tiling over or do you intend to finish skim the Bonding? Either way, I frequently use Bonding on deep wall repairs, cable chasses etc, levelling & tapering it far, far less than 5mm without any problems. Bonding is very coarse but, with practice & good technique, you can still get a reasonably smooth transition which is perfectly good enough for tiling over or skimming, you don’t need to achieve a perfect feather edge it won’t matter. Using too much water is the main cause of problems, only use just enough to keep the trowel moving & prevent you ripping it off the wall; but that’s true for any plaster.

 

[deko]

Resurrecting this post since the content is relevant.

I am installing a shower and so want to Tank the walls before I tile over them. Would the following sequence be acceptable.

1. Tank the wall.

2. Fill & Feather the entire wall to make level with "powdered" waterproof wall tile adhesive then allow it to dry.

3. Tile over "levelled wall" making adjustments with pressure & extra adhesive (if necessary) as I go along.

My question is, would it be ok to change the order, like this...

1. Fill dips in wall using tile adhesive.

2. Tank the wall.

3. Tile over wall.

Or is it better to tank first then fill the dips?

Many Thanks
d.