Fixing tiles onto bonding

[nh26302]

Hello,

 

I had had a shower room tiled around 3 yrs ago with natural stone tiles and recently noticed one of the tiles had moved out.

 

Just got a builder in to have a look and basically all the plaster behind the tiles (and adhesive) has crumbled away.

 

The plan initially was to fix a hardie backer board and tile onto that but when the builder removed the affected plaster there is a brick wall and he said it's not possible to fix the backer board and as it had been bonded previously, he removed all the loose bonding and has just put bonding on it again and said he will be back in a couple of days to fix the tiles directly on to it.

 

By chance, I was searching on line and came across a few posts suggesting that fixing tiles onto bonding is a no no. 

 

The bonding is currently drying and I'm wondering what is the best approach going forward....should I get him to skim over the bonding with multifinish and then wait a couple of weeks to dry before tiling?

 

I've also read something about using a primer like sbr on the bonding and then tiling on top of that? If that works, is it just a case of "brushing" the bonding with the primer, letting it dry and then using tile adhesive to fix the tiles onto it?

 

The builder had also asked me to get pva which he brushed on the brickwork before applying the bonding (not sure if he also mixed it in the bonding) but it seems like pva is also not the way to go from what I have read?

 

The affected area is around 1sqm and this is what has been bonded (again). It was initially thought that as the bottom tiles were affected, maybe the silicon wasn't applied properly between and the bottom tiles and the shower tray and this caused water to seep through, however, thinking about it, it is probably the fact that it was bonded before and the tiles being natural stone also allowed moisture to seep through?

 

Anyway, the builder is back Tuesday and I would really appreciate advise on the best way forward.

 

Thanks in advance

[nod]

You can’t fix tile on to bonding 
It will need to be skimmed 

 

I wouldn’t use bonding in a wet area as it acts like a sponge and crumbles 

Bit late now but he could have dabed Hardy backers on the used  a knockin to mechanically hold the backers 

[nh26302]

Thanks Nod,

 As the area is small, I was thinking of maybe getting him to remove the bonding and just sand cement it instead. Would that be better than skimming or is skimming the way to go?

 

Thanks

[nod]

Probably better in sand and cement 

Most of the backing plasters are outdated now 

[twice round the block]

You could skim, depends on the thickness your trying to make up.

 

I've used out of date multi finish before as it cures faster ( if it's really out of date it goes off in the bucket ) 🙄

[nh26302]

Thanks....

 

What would be better, apply a skim to the bonding or replace bonding with sand/cement?

 

Also, which would dry quicker as I would like to get the shower room functioning as soon as I can.

 

Many thanks 

[bassanclan]

If you are have the chance then dab and frame fix hardie backer board

[nh26302]

Maybe I'll get him to remove the bonding and if possible to fix hardie backer then go with that otherwise, will get him to sand cement it.

 

For fixing the backer board, is it better to use PB adhesive or adhesive foam? 

 

Also, for fixing the anchors, is it just a case of drilling a 6mm hole through the board once it has been fixed with adhesive and then push these fixings through it and fasten? 

 

 

https://www.screwfix.com/p/fischer-nylon-hammerfix-6mm-x-40mm-50-pack/57635

 

Thanks