Bathroom floor layers

[SaudisLoveAudis]

Hi All,
I hope you are doing well.
I have screwed the floor boards so I don't have any movement and squeaks.
I have put extra 5mm ply wood on top and screw them in.

Now I have these items:
1. STS screws and washers
2. STS 10mm insulation boards
3. EVO-STIK 1L Flexibond Tile Adhesive Primer

I think I should prime the plywood before I put the adhesive and STS boards
What primer can I use for that? I think regular red Evostik PVA isn't good.
The primer below is going to be added into the adhesive.

Thank you

 

[tell80]

OP,
Have you taken into account that all fixtures (eg. the WC) and skirtings will end up in a high FFL? ie. your finished surface will be much higher than now?
Your FFL will also be high at the door threshold.

The 5mm ply is incorrectly screwed down. You should match screw all joins 20mm from the join at 150 mm centres. The field should also be screwed down at 150mm squares.
Is the ply being used to patch in a 5mm low area repair?
Backerboard can be fixed to the floor boards - no ply is needed.

 

[SaudisLoveAudis]

OP,
Have you taken into account that all fixtures (eg. the WC) and skirtings will end up in a high FFL? ie. your finished surface will be much higher than now?
Your FFL will also be high at the door threshold.

The 5mm ply is incorrectly screwed down. You should match screw all joins 20mm from the join at 150 mm centres. The field should also be screwed down at 150mm squares.
Is the ply being used to patch in a 5mm low area repair?
Backerboard can be fixed to the floor boards - no ply is needed.

I know that the floor is going to be higher than it was originally.
Before there was a similar 5mm plywood and floor covering. I reckon 8mm in total.
Let's say I take off the ply and use only STS this will be 10mm STS + 10mm tiles + 2x layers of adhesive another 10mm?
So I end up 22mm higher than it was. I can cut the doors no problem. What I am more worried is the existing soil pipe.

I put down the plywood to make it very even across the board. In the past someone lifted a couple of boards but now they kind of not in line with the surrounding floor boards so I though maybe it's a good idea.

Thanks.

 

[cdbe]

Seems to be a few ways, I secured the existing floorboards, primed with SBR then fixed 6mm cement boards (also primed) with flexible tile adhesive and screws, primed top face and tiled, with flexible tile adhesive. I'm not sure what your ply is adding.

 

[SaudisLoveAudis]

Seems to be a few ways, I secured the existing floorboards, primed with SBR then fixed 6mm cement boards (also primed) with flexible tile adhesive and screws, primed top face and tiled, with flexible tile adhesive. I'm not sure what your ply is adding.

Ok so I take off the plywood then. Where can I get the right SBR?
Topps Tiles has this BAL Primer that has bad reviews.
Should I buy Sika Bond SBR+ Waterproof Bonding Agent and Mortar Admixture - 5L or
KA SBR Bond Co-Polymer Bonding Compound 5l from WIckes.
OR BOSTIK SBR ADMIXTURE WHITE 5LTR crom Screwfix?

 

[cdbe]

If you don't need much, Wickes do a handy little 1 litre pot of the KA for £6.50.

 

[SaudisLoveAudis]

If you don't need much, Wickes do a handy little 1 litre pot of the KA for £6.50.

Just a side note. Isn't easier to dismantle the floor in the future if I have this layer of plywood so the floorboards don't have adhesive on them and won't get damaged during the dismantling?

 

[cdbe]

I'm sure it would be, but personally on a £5,000+ bathroom I'll worry about replacing a few floor boards in 10 or 20 years time.

 

[SaudisLoveAudis]

Ok, I have undone the plywood and I put an insulation board with adhesive and the screws
Unfortunately my pattern recognition was not working properly at the time. I hooked up on some other pattern I wanted to avoid but then somehow I put two exact tiles next to each other in the exact orientation.
Moreover working with this Mapei Flexible Rapid set bit me the second time. I made about 2/3 of the medium size (black) bucket of adhesive but I hardly managed the half of it before it started setting (was unworkable already) so I though I dilute it with water a bit but after excessive mixing I was not able to get rid of the chunks that already formed.
So I started ripping the affected tiles one that was glued using the bad adhesive and the second in wrong orientation. To get to the wrong one I had to remove the bad glued first anyway.
Now I have a hole up to the lower layer of the insulation that still sticks to the bottom adhesive.
Do I have to rip the whole thing down to the floorboards? Or is there another way?
I have already chipped a nearby tile but I can live with that if I have to go deeper I reckon I cause more damage and end up ripping the whole thing to the first tile I put.

Is there any flexible adhesive that is setting longer than 3h? There is this standard one that dries for 24h but I haven't come across a flexible one. I reckon flexible should go on the floor. Inflexible can go on the walls.
The temperatures are still under 20 centigrades but this makes no difference. This adhesive is done after 20 minutes.

 

[cdbe]

I used Mapei Keraflex Maxi S1 Flexible Floor Tile Adhesive (8hr pot life, 30min open time). I don't know why the DIY sheds sell rapid set adhesive, it's extremely difficult for a non professional to use.

Unfortunately you've used insulated boards rather than solid cement board - looks like scrap, especially after you've remove the rest of the adhesive. If you didn't get any of the other tiles down within the specified time I would be suspicious of the bond!

 

[SaudisLoveAudis]

indeed. With rapid set I don't see a point of making more than half a bucket of adhesive (about 2 litres of water).
If it's more than that there is not enough time to use it especially when I put adhesive not only on the floor but also on the tiles themselves to get 100% coverage.
I reckon experienced tilers can do it quicker however these 60x60 tiles are cumbersome to work with anyway.

Anyway I have levelled the area and put new tiles already. I think it will hold.