Re-tiling over old adhesive

aetbaar

Hi

I need to tile my bathroom and having removed all the old tiles there is some old adhesive still stuck on the walls- probably 20-30 years old which is very hard to get off

I wanted to just apply some BAL primer on top having got the loose bits off and then tile straight on top. I do realise that most people advise to get the old adhesive off first and then maybe reskim but just wandered if I could tile on top of the old adhesive

Also some of the skim has come off with the old adhesive in some places and left the plaster / concrete rough layer beneath it- can I apply primer and then tile directly on to this or do I need to get it skimmed first

I realise the BEST way would be to reskim or hardwall all of the wall and then apply tiles but wanted to know if I can try and work with what is already there

Also do I need exterior grade 18mm plywood to put on the floor – is this waterproof or will I need marine ply?

Thanks in advance for the advice

andyhop

I would remove the rest, it will leave a flatter wall. Use a Hamilton scraper with a 5 inch blade

Prime walls with mapei or bal primer then repair walls with rapid set tile adhesive. Don't use plaster or you could be waiting weeks before you could tile

15mm marine ply is thick enough for a overlay with a 2 part flexi S2 adhesive. 18/22/25 if replacing . I would suggest to spend the extra on marine, we have had a few failures recently on standard 25mm plywood that is shrinking months down the line and creating hairline cracks through the tiles. Tiles are still solid !! Modern plywood is rubbish compared to that of 10yrs ago, many species of softwood that's now being used in place of a hardwood core and face

aetbaar

Thanks for the advice

If a little tile adhesive is still left on there does that matter as some of it will be hard to get off and take a lot of plaster off with it if it does come off. In that case I assume can just prime over the old adhesive and then cover with rapid set tile adhesive before tiling

When you say to prime and then put the rapid set tile adhesive do you mean to put the primer on the concrete/ plaster wall that is left behind the old tile adhesive and then put the rapid set on and allow to dry before then putting more rapid set glue on and applying the tiles or would you put the tiles straight on to the rapid set that you put on after applying the primer

Is exterior plywood from wickes or B&Q good enough or would it need to be marine specifically- it is not a wetroom just a bathroom with a separate bath shower sink and toilet

Thanks again

andyhop

Prime first, apply rapid set . I would leave it to set before tiling , can always scrape back an high points then

Can't comment on shed quality, not something I use

aetbaar

Having looked at this further adding 15mm plywood and then the glue and tiles will add a lot of height

Do I have the option of putting down aquapanel instead using flexible adhesive as it's a lot thinner and hopefully will have the same effect

Other option is to pull up the original chipboard and then lay the marine ply on the joists but that could be considerably more effort

andyhop

You could use 6mm hardibacker board, glue to floor with a rapid set S2 adhesive then screw once set . Tile with S2 adhesive

15mm ply will leave a step but a bit of oak chamfered will leave a tidy finish that isn't a toe stubber

aetbaar

I think I will go for the backer board as suggested

Is the bal ultrafix the best s2 adhesive to go for or can you recommend any others

Do I need to prime the floors first before applying the glue

If so what primer would you suggest I have seen the floor tile primer and admixture at wickes is that ok to prime the floor with first

Also can I not tile on top of existing floor as it is

I have removed old floor tiles from 30 years ago and there is still lots of very hard floor adhesive stuck to the chipboard which is impossible to get off - should I just apply primer and tile directly to this and tile on this as it looks solid or should I lay the tile backer boards as suggested

What I don't understand is that if I apply the tile backer boards they are still stuck to the chipboard which is subject to movement and coming lose so what difference does it make ?

andyhop

Mapei Keraquick with latex additive is the best out there, its just the high cost as its a £50 2 part mix for 20kg

Prime with Mapei primer G, I would suggest you visit your local CTD as they sell backer boards, adhesive etc and should work out the same price or cheaper than a shed for a better product

There is mesh that can be used on chipboard floors, but we would always remove or atleast overboard with 15mm ply. We don't get failures this way but I do has many friends who have used 6mm Hardi again with no issues. No adhesive manufactor will suggest or warranty tiling straight over chipboard

I can only give advice what's worked for us for the last 10yrs in bathroom and kitchen fits

aetbaar

Can I use mapei mapeker rapid set flex it says it is single part flexible adhesive ?

Or does it need to be keraquick ?

aetbaar

I also see the wickes flexible rapid set tile adhesive is s1 and has good reviews would that suffice or do I definitely need the expensive s2 stuff

As I am sticking backer boards to floor and then tiles to backer boards I will need twice as much which could be costly

andyhop

No shed adhesive is going to be as good a proper trade adhesive from Bal or Mapei .Expensive yes but do the job right . Cutting corners could leave you with popping or cracked tiles, the cost of adhesive can be penny's when your using high quality tiles

I was once given a sample of the mapei stuff sold at B&Q, 2 days later you could pop the tiles off with a spatula and the adhesive when set was still very powdery and crumbled when rubbed between your fingers