tanking straight onto bond coat

[aflemi]

Apologies if this is duplicated, site navigation problems............
I have a plasterer doing my bathroom, in the shower area I intend to tank it. Can I apply tanking straight onto bonding coat or do I need him to appy a skim over the bond before I tank it? walls are solid ie not plasterboard or dot'n'dab. thanks help

 

[grumpygrouter]

Bonding coats are not suitable for tiling onto so I would say yes you need to have the finish coat. Bonding is really absorbant I believe so your tanking may not be successful without the finish skim.

 

[White Room]

Put a finish on it, the bonding coat can be course and you may have trouble filling the surface

 

[grumpygrouter]

I was hoping you might be around to answer this Whitebeam...

 

[White Room]

Good answer though Russunk:

 

[aflemi]

Great thanks, I thought that was best. How long approx should I leave the plaster to dry before tanking, it will be a pretty thin coat.....

 

[grumpygrouter]

If you have had the whole thing done with a new base coat then tiling will need to be delayed for sometime, up to a month depending on thickness of plaster.

 

[lucius]

Why did he use bonding, hardwall would have been better i know it is being tanked but i dont like bonding in any wet situation it just seems to attract moisture from the air and stay damp.
Andy

 

[davy_G]

Is it bonding or scratch coat?

Ive tiled over scratch coat many times and tanked onto it.

Why would they bond a shower area? Usually over here they only bond ceilings.

 

[White Room]

Bonding, Hardwall are all gypsum products and would attract moisture

 

[doug boardley]

would have knocked it off and sand/cement rendered myself

 

[lucius]

Quite correct White beam i think the proper termanology is hygroscopic where something attracts moisture from the air and stores it within itself the trouble is with bonding it just seems worse at doing it than anything else.The only worse material i have found for this is plaster of paris that is like a sponge when their is moisture in the air.A concern i have about this is the use of one coat plasters, even though i use them myself, in older houses where the walls need to breath and their is always a certain amount of moisture in the wall as i have found that the problem is always worse when gypsum products are put on thick. One coat is a modern conception so only use it on modern structures.
Andy

 

[Ren+]

Quite correct White beam i think the proper termanology is hygroscopic where something attracts moisture from the air and stores it within itself the trouble is with bonding it just seems worse at doing it than anything else.The only worse material i have found for this is plaster of paris that is like a sponge when their is moisture in the air.A concern i have about this is the use of one coat plasters, even though i use them myself, in older houses where the walls need to breath and their is always a certain amount of moisture in the wall as i have found that the problem is always worse when gypsum products are put on thick. One coat is a modern conception so only use it on modern structures.
Andy

What would you do on a lath&plaster wall that strips down to the lath when removing old tiles. Let's say it's going to be a wet area wall. What would you use to repair the wall before retiling. Assuming also that no tanking will be done.

Thx
Andre

 

[White Room]

Remove the lath and plaster and fix 12.5mm hardie

 

[doug boardley]

What would you do on a lath&plaster wall that strips down to the lath when removing old tiles. Let's say it's going to be a wet area wall. What would you use to repair the wall before retiling. Assuming also that no tanking will be done.

Thx
Andre

a 12mm hardibacker type board Andre

 

[aflemi]

Why did he use bonding, hardwall would have been better i know it is being tanked but i dont like bonding in any wet situation it just seems to attract moisture from the air and stay damp.
Andy

The situation was that the enclosed (3 walls) shower area was previously fully tiled on solid plastered walls. I removed the tiles and scraped off old adhesive. In doing this then some of the finished surface below was bound to come off, leaving up to 3-4mill diffirence on surface levels. Also there were gaps up to 25mil deep back to blockworkjust above the shower tray where it had been shoe'd in. I asked the plasterer to do a levelling bonding coat, then, on the advice above, a finishing skim. Apart from right at the base the bonding would have been no more than 4-5mil thick, I also think he filled the really deep gaps with a quick drying filler. I would have put backing boards all round but didn't have the room to increase wall depth or shower door would then have been too wide.
What better alternatives would I have had please?
Also in light of the above extra info on depth of plaster applied, how long do I leave before tanking?
Again many thanks for input, very useful.....

 

[grumpygrouter]

The situation was that the enclosed (3 walls) shower area was previously fully tiled on solid plastered walls. I removed the tiles and scraped off old adhesive. In doing this then some of the finished surface below was bound to come off, leaving up to 3-4mill diffirence on surface levels. Also there were gaps up to 25mil deep back to blockworkjust above the shower tray where it had been shoe'd in. I asked the plasterer to do a levelling bonding coat, then, on the advice above, a finishing skim. Apart from right at the base the bonding would have been no more than 4-5mil thick, I also think he filled the really deep gaps with a quick drying filler. I would have put backing boards all round but didn't have the room to increase wall depth or shower door would then have been too wide.
What better alternatives would I have had please?
Also in light of the above extra info on depth of plaster applied, how long do I leave before tanking?
Again many thanks for input, very useful.....

Generally allow 24hrs/mm thickness of plaster. it is not just the drying that you need to look out for. The plaster can appear "dry" but it will not have reached full strength. It needs to be as strong as it will get to support your tiles.

 

[aflemi]

Thanks, Grumpy. Also on the alternatives... If I can avoid getting a plasterer in, I would like to know alternatives for future in a similar situation, apart from backer board, obviously.
Many thanks again.

 

[lucius]

Now you have explained it their is not much more you could have done other than hacking every thing back to the render and doing it again in sand and cement but this would very much depend on the strength of the render and what kind of blocks it was on and maybe a bit over the top.The only thing differrent i may have done would be to have used one coat plaster as it would been done in one hit.It is always better to put finish on top of bonding the same day as if it drys out the finish tends to bubble in this situation most plasteres would unibond first but here in a potentialy damp situation i would SBR just to be sure.
Andy

 

[aflemi]

Great, I'm sure that's the first step on the tanking procedure, thanks.
Also thanks to everyone for their input.

 

[davy_G]

Thanks, Grumpy. Also on the alternatives... If I can avoid getting a plasterer in, I would like to know alternatives for future in a similar situation, apart from backer board, obviously.
Many thanks again.

Turn your tilers trowl round and skim it yourself with rapid set.
Tile in 3 hrs, no one else needed. Bingo.:hurray:

 

[Dan]

Just bumping some of the older popular (sometimes not so popular) threads. Probably wont be current discussion these days but I just need to do it. So just ignore the thread if it's not current for you.