Tiling Questions - Porcelain tiles on PB/wood

9 Feb 2009
Reaction score
United Kingdom
Hello All, I am new to this forum and although I have had a good read about, I would like to ask some questions/get some clarification on my situation, so please forgive me if I have asked something which has come about before.

I am in the process of re-doing my en-suite and have chosen some 600x300mm porcelain tiles (about 9/10mm thick). Only after reading this forum have a I realised just what issues this might lead to!

My walls are plasterboard (existing, so plastered and painted with what looks like that bathroom paint). The shower area I have has had the PB stripped down (due to removing old tiles) and will have a new tray put in.

1. Would I be ok to use normal 12.5mm PB and then tank with BAL WP1 kit or should I use moisture resistance PB or something else?
2. If using normal PB, should I tape it with normal PB tape or does the kit come with special stuff?
3. Are there any other alternatives to the BAL WP1 kit that are any good?

Regarding the tiles - I hadn't appreciated the weight limits for plasterboard and plastered PB. What is your advice on what to do with the existing painted walls? Will this take the weight of the tiles OK?

Behind the wall hung toilet/sink and also on the floor I plan to use ply. Is 18mm ok for this? The floor currently is 18mm T+G floor boards. It was previously tiled (with cermamic tiles) which I have taken up but its left a load of flexi adhesive everywhere.

Therefore, I am planning on ripping most of the floor up, but I will have to leave a few inches around the edges as the internal walls were built on top of the flooring (new ish house!!) making it difficult to sort out. This is why I plan to use 18mm ply - to match what will be around the edges of the floor!

Regarding the BAL WP1 product, this is a tanking product - so I presume that I won't need to use a primer also and can just apply direct to PB and then tile ontop?

Finally, will the porcelain tiles (polished) need sealing at all? If so, then I presume this will need reapplying everyso often? Again, what products are good?

I have seen links for diamond drill bits which was useful, thanks. Am a tad concerned about the costs to just cut the tiles though - was thinking about a manual cutter and an electric one (so I can cut notches etc) wich diamond wheel. HSS hire a 230mm one - any good?

Am wondering if its worth spending out on a Rubi cutter (manual) or if there is a cheaper way? Will say the TS-60-PLUS cut these tiles with no problems?

Sorry for all the questions, but I thought I had started to get this work sorted, but now its all been thrown up in the air!
Sponsored Links
plasterboard is fine once its tanked.

Tanking kits come with tape.

Dunlop tanking kits are not bad.

Sand and off the paint and prime with acrylic primer.


You need to weigh the tiles and allow for adhesive and grout too.

25mm ply is better for a floor.

tanking kit should come with primer and full instructions.

Porcelain shouldn't need sealing.

A wet saw and manual cutter depends on your budget and how much tiling you have to do.
PB ok to tank
You get tape with kits
Alternative to tanking is Homelux matting
Painted walls will need to be sanded & keyed, use acrylic primed only, NOT PVA, BAL APD or similar
Definate weight issue, check link in lancenotalots post
18mm ply ok, BS is 15mm which you rarely get so 18mm next best thing
Polished porcelain will need to be sealed, 2/3 coats to avoid staining & every 12 months. Check small offcuts 1st & test.
Cutters depend on budget & lifecycle etc, will you use again? We use Marcrist bits, expensive but excellent cutting & life.
Cheers for your answers. Think 18mm ply is enough. Went to Wickes (not to buy, just to look honest) and its thick enough. 25mm is harder to get too and would cause me issues when I meet the existing 18mm T&G at the edges.

I had a call from Rubi this morning (nice guy too) who said porcelain is very hard to cut, but he would recommend the speed 62 which should be ok as only would use if for ensuite and possibly bathrooms (i.e. DIY and not every day for job!), or the TR-600.

Both recommended basically as the tiles are 600mm long, a single point breaker might not work so well, and the above 2 are sort of multipoint (or the breaker is on the slider so can do in middle of tile).

I am a bit tempted to just buy something like the Rubi ND-180 or something as can do it all though not sure if table size if big enough for the tiles.

Weight will be decider I think. Existing 12.5mm plastered PB will probably not cope with it and theres not much chance of me taking all the wall boards off just to redo and tile - though I might if I get bored!! :)

Saw some Aquaboard too today, looks a pain to cut and board sizes are smaller than PB (ones I saw anyway). So probably just easier to PB and tank.

Might have to expanding foam the tray into the gap - around edges as PB on the 3 walls will come to just above tray so the open walls and stud work won't but against the tray - gap is a tad big at around 780.

Looking at Ideal Standard Simplicity - Idealite tray - are they any good? Guess they can just be bonded or silicon'd to the floor? As piping will go under the floor, thought riser legs would raise trap to above floor level so making the waste a pain.
Sponsored Links
Oh and forgot - some places say porcelain doesn't need sealing as it is not great at soaking in the water. Hence partly the reason for special adhesive.

But others say seal - does anyone know why the difference - is it tile dependant?

Tiles are from Ceramic Tile Warehouse in Camberly. They seem ok, but not had a chance to speak to them about all this yet.
Kev - many reasons for sealing, porcelain, especially polished can stain easily & will show up so sealing is required. We always seal!

Best way to check is to get a small cut off & throw everything you can at it, a little veg oil, a bit of ketchup, a little bit of soap suds, a drop of red wine etc in different spots on the tile, leave for a while & wipe off, you will see where they have marked the tile.
umm, true. I don't mind being safe than sorry, its not exactly a hard job eh!

I guess its just wipe on and leave to soak in? How long do you have to leave it etc?

Anyone used these diamond bit kits? - the bathroom fitters kit in particular
depends on the manufacturer kev, you wipe/brush on leave for 10/15 mins & wipe the residue off or these leaves a stain itself, just aim for a consistant coat across the tile.

365 drills ok but you get what you pay for, we use Marcrist cos they use real diamonds & not synthetic diamonds, 365 will probably get 15/20 holes drilled while the Marcrist will get 50/60 in porcelain so depends on budget again
Like everything in life I guess. Thanks for yoru help though.

When I buy tools, I do like to buy ones which are decent make and reliable so will lat a lifetime. But then I have to remember I am a DIY'r and could save a lot of dosh by just getting by - but its against the grain so usually cannot do it!
18mm ply ok, BS is 15mm which you rarely get so 18mm next best thing.

Paul if you check the ops first post you will see he is talking about removing the existing boards and replacing with ply,I think from your post you are talking overboarding.

When replacing 25mm would be the way to go IMO.
bummer. that would cause me an issue where the new floor meets the existing at the edges - as this is only 18mm or so.

Guess I could overboard that with 6mm to level it a bit. The adhesive will take out any difference I guess?

The more I think about it, the more I am leaning towards stripping all the PB off the walls and putting new up so I can tile with Porcelain and not have to trail around looking for ceramic tiles I like!

Was thinking about putthing the green (Moisure) PB up as room can get a bit humid, even though tiling and sealing over, just more as a precaution than anything else - never had an issue up to know so should be ok with normal.

Wishing I never started this now!! :(
ah sorry guys missed that bit.

25mm ply then

or secure floor boards & use 6mm hardibacker/no more ply boards


3mm schluer ditra matting
I appreciate the advice, but surely 18mm has to be enough for a small floor area - 25mm seems overkill and would cause a big headache with edges! Plus what with the 10mm tile thickness, there would be a big difference in floor height between this and the bedroom.

Do you think if I added more noggins across the floor joists and used 18mm if that would be enough? Afterall, most floors in houses are 18mm T&G anyway.

18mm screwed every so many inches would surely not move that much - and with flex adhesive should be fine?? Floor area is so small anyway!!

Either thickness, I presume I would need to seal the wood before laying adhesive?

My understanding is, tank the shower PB area, seal the rest of the PB and wood before any adhesive - is this correct?

Any recommendations for the sealant and adhesive (and grout) would be greatly appreciated - plus anywhere cheap to buy it all! :)

DIYnot Local

Staff member

If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

Select the supplier or trade you require, enter your location to begin your search.

Are you a trade or supplier? You can create your listing free at DIYnot Local

Sponsored Links