Bathroom Floors and Walls - Again

[Alucard7002]

Another DIYer seeking advice. I had bought most of my materials (on the advice of the Topps Tiles shop) before I found this forum. Having spent hours of reading I think I may have to take most of it back! But before I do so I would appreciate the professionals’ input.

It is a first floor en-suite bathroom approximately 2.2m x 2.4m. I have stripped off all the old plasterboard from the two stud walls and will be stripping off the existing 18mm T&G chipboard flooring.

Floor:

The floor joists are 200mm x 50mm (8” x 2”) at 400mm (16”) centres. The existing floor creaks a little (but far less than the rest of the house) but when I jump up and down in the centre I can detect no discernable deflection or bounce (unlike some other rooms!). I plan to put in 200mm x 50mm noggins on 300mm centres well glued and screwed.

The tiles are nothing-special 8mm ceramics with a nominal weight of 16kg/m2. The adhesive I have is Topps Trade Rapid-set flexible wall & floor tile adhesive BS EN 12004 C2FT and the grout is Grout is BAL microflex Microban.

I had planned to put down a new 18mm WBP ply floor, glued and screwed with Spax 4.5mm x 60mm Flooring Screws at 150mm centres everywhere, but I have read numerous references to 22mm or 25mm as the minimum. If at all possible I would like to use the 18mm for 2 reasons:

1. The usual one of the ‘step’. The existing bedroom carpet lies about 12mm above the existing 18mm bathroom floor, so with 8mm tiles plus nominal 4mm bed it’s a perfect match. But with 25mm floor it obviously will be 7mm higher. SWMBO is very concerned about the aesthetic effect and fears stubbing her toes on this ‘step’.
2. I’ve managed to get the two 1220mm x 2440mm sheets of 18mm ply upstairs – just. That involved flexing the sheet to the maximum possible to force it past the banister and wall – I’ll have to repaint the wall! There is no way a 25mm sheet can flex enough to do this so it would have to be ripped along its length into two 600mm wide ‘strips’. With the 18mm I already have, I can rather neatly use two complete sheets with only one joint, but with 25mm I would have to three joints.

Question 1:
Would 18mm ‘do’, or is it absolutely essential that I battle it back downstairs and change it for 25mm with a lot more joints?

Stud Wall:
This will be one wall of the shower; the other is a traditional plastered block wall. The stud-wall is 80mm x 50mm (3” x 2”) verticals with only one run of horizontal noggins at the midheight. I plan to add 80mm x 50mm noggins at 300mm centres. I have bought 12mm WPC ply, Homelux Waterproof Matting, BAL grip BS EN 12004 D2TE and BAL microflex Microban. The tiles are nothing-special 8mm ceramics with a nominal weight of 16kg/m2.
If I used the ply - glued and screwed as the floor - I would have a nice single sheet with no joints in the shower area.
But I have read comments saying ply is a no-no and strongly recommending backing board instead - something like this:

Wickes *–*Building Materials*–*Plasterboard*–*Aquapanel Water Resistant Backing Board

I’m confused!

Question 2:
Should I wrestle the 12mm ply back downstairs and change it for the backing board – which would have a lot of joints?

Oh – last point; we built this house in 1990 and plan to live here for the rest of our lives, so I do want a ‘proper’ job, not just a ‘bodge it’ for a quick sale job.

 

[trevortine]

If you want a proper job then get a pro in to do it for you. Otherwise, fitting tiles onto plywood doesnt mean you lift the existing floor and replace with the ply. It means you overboard and screw at 150 mm centres to beef up floor, unless there is deflection there that needs repaired. British standards, manafacturers recommendations, anything from 12mm to 18mm, if im overboarding chipboard i use 9mm ply, glued and screwed and have never ever had a problem, some people use ring shanks, waste of time imo. Make sure its well screwed and thats more than adequate for a domestic installation. As for your walls you can use either plasterboard or cement board, tanking the wet areas as you go. Many dont bother but the amount of water damage ive seen over years i feel justified in doing so in almost every job i do. Hope this helps, feel free to ask away and welcome to the forums:smilewinkgrin:

 

[jimbob]

For your floor, as far as I am aware, you can replace T&G floorboards with WBP ply straight on to joists, and if so 18mm is the minimum recommended. Most people recommend more (ie 22 or 25mm) as belt and braces but as long as you fix securely at 150mm centres it should do the trick..

 

[Alucard7002]

If you want a proper job then get a pro in to do it for you.

True enough! But having taken a semi-voluntary early retirement I'm time-rich and cash-poor. Besides, I always like to have a 'project' on the go and learning new stuff keeps the old brain cells working.

Otherwise, fitting tiles onto plywood doesnt mean you lift the existing floor and replace with the ply.

One corner of the existing floor under the shower was damp and swelling. A lot of the rest has to come up to run new central heating pipes to a towel rail in a new location. Then another area has to come up to run the plumbing to a new location. So I would be replacing the whole floor with new anyway. The question becomes with what?

For your floor, as far as I am aware, you can replace T&G floorboards with WBP ply straight on to joists, and if so 18mm is the minimum recommended. Most people recommend more (ie 22 or 25mm) as belt and braces but as long as you fix securely at 150mm centres it should do the trick..

So my 18mm WBP ply is OK

As for your walls you can use either plasterboard or cement board, tanking the wet areas as you go

I’ve bought 12mm WBP ply and waterproof matting– use that or exchange it for the Wickes backing board (with or without the matting?)

 

[CON5933]

On the adhesive side...where it says Rapid on the topps rapid set...it means it..VERY RAPID
With the homelux matting, be sure to use a cement based adhesive like the rapid set etc...not the tubbed gear. ..for the installation and the tiling onto..

 

[CON5933]

personally I wouldn't reccomend PLY for walls. I'd go for the cement backer boards and i'd still use the matting...

 

[Alucard7002]

On the adhesive side...where it says Rapid on the topps rapid set...it means it..VERY RAPID

Noted. Thanks for that, maybe I should do a little cup-sized test mix first to get used to it. I've been caught out with that before when using coving adhesive, all going fine - then BAM it's all gone off without warning!

With the homelux matting, be sure to use a cement based adhesive like the rapid set etc...not the tubbed gear. ..for the installation and the tiling onto..

oh, why is that? Is the [FONT=&quot]Topps Trade Rapid-set flexible wall & floor tile adhesive exactly the right one or should I get a different cement based one? Topps or Wickes is my closest supplier.
[/FONT]

 

[Alucard7002]

personally I wouldn't reccomend PLY for walls. I'd go for the cement backer boards and i'd still use the matting...

So back to Wickes and exchange the ply for their backing boards then. What do I use to seal/tape the joints? Some special product or just butt them up tight and cover with the Homelux stuff?

 

[CON5933]

The topps gear is fine.
Because the matting is waterproof you will be sealing the adhesive in, no air will get at it, the tubbed gear is a 'dispersion' adhesive, it needs air to get rid of the moisture content and set.. The cement based adhesives ahve an addative and set through a chemical reaction. The same reason you can't use tubbed gear on large format tiles, the adhesive in the middle of the tile would still be wet while the outer edge would set.
The same when tiling onto the matting, there will be no absorbtion and very little dispersion so use the same cement based adhesive for the tiles. check if you need grey or white adhesive before you start..

 

[jimbob]

Topps do BAL adhesives and grouts, which are generally considered one of the best manufacturers, if a little pricey

 

[CON5933]

So back to Wickes and exchange the ply for their backing boards then. What do I use to seal/tape the joints? Some special product or just butt them up tight and cover with the Homelux stuff?

I leave a couple of mm between each board. If you're covering all the boards with matting then no need to tape, just fill the gaps with rapid set until flush... then cover with the homelux stuff.
if you have a look at my photo album 'Bathroom', you'll see the same method from start to finish with cement boards in the wet areas covered with the matting.

 

[Alucard7002]

The topps gear is fine.
Because the matting is waterproof you will be sealing the adhesive in, no air will get at it, the tubbed gear is a 'dispersion' adhesive, it needs air to get rid of the moisture content and set.. The cement based adhesives ahve an addative and set through a chemical reaction. The same reason you can't use tubbed gear on large format tiles, the adhesive in the middle of the tile would still be wet while the outer edge would set.
The same when tiling onto the matting, there will be no absorbtion and very little dispersion so use the same cement based adhesive for the tiles. check if you need grey or white adhesive before you start..

Perfect sense! Easy when you know how isn't it!
I bought grey, not entirely sure why now! The tiles are cream/very light brown (dull sludge) and grout is white, so now that you have nudged me, maybe I will change it for white. I'll get some of that Corner Tape while I'm there too, my silicone handling skills are good enough for garage/shed but not for SWMBO's bathroom.

 

[CON5933]

Good idea, my mrs is the same
I haven't used the tape but it certainly does look like the answer. Silicone joints and grout lines can make or break a job. Good luck

 

[Deleted member 9966]

boys

what does SWMBO stand for?

 

[jimbob]

She Who Must Be Obeyed!!

 

[Deleted member 9966]

She Who Must Be Obeyed!!

:yikes:

 

[Alucard7002]

boys

what does SWMBO stand for?

Otherwise SWMABO

She Who Must ALWAYS Be Obeyed.

AKA The Ultimate Authority, The Boss

 

[Alucard7002]

Comes from John Mortimer's books about Rumpole of the Bailey.

John Mortimer - Wikipedia, the free encyclopedia

 

[Diamond Pool Finishers]

all women tend to be darleks "you must obay"

:lol:

 

[Time's Ran Out]

If you are using the cement based waterproof backer boards why are you using the waterproof matting as well?

 

[CON5933]

If you are using the cement based waterproof backer boards why are you using the waterproof matting as well?

belt & braces.... for the sake of a few quid it can't hurt

 

[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.