Levelling and tiling en-suite floor with Mapei Ultraplan Renovation

[Stompfrog]

Hi all,

I'm an enthusiastic DIY'er (first time poster) who has been slowly chipping away at an en-suite bathroom renovation for a few months. Last night I went to install the shower tray (1600 x 900) and I realised that the floor by the drain end was about 10mm higher than the floor at the other end. This slope continues across the whole room. I've concluded that the best solution to this problem is to use some self levelling compound as not only will this level the shower tray but it should help get a better finish on the floor which is being tiled with 1200mm wood plank porcelain tiles.

As you can see in the photo, the floor is 22mm chipboard which is glued down in the older parts and screwed where I have replaced some boards. I've measured about 20 places across the floor using a laser level and I think the worst dip is about 13mm by the door. It also looks like a previous owner has already used some kind of leveller in the central part of the floor.
I just wanted to run my plan past some more experienced bathroom installers to get confidence that I am heading in the right direction before diving in.

1. Trim back the plasterboard/tile board where it meets the floor to ensure decent clearance from the raised floor level (where needed).
2. Briefly sand the floor with a course grit and hoover.
3. Wash the floor.
4. Fill the joints in the chipboard (and a couple of old screw holes from the old toilet with silicon)
5. Use silicon to seal between the wooden/metal sole plates and the floor on internal walls.
6. Use expanding foam to seal the gaps between wall and floor on external walls.
7. Use expanding foam to create a dam around the shower waste hole.
8. Prime the floor with Eco prime grip plus.
9. Level the floor with Ultraplan renovation.
10. Trim back the excess foam and marvel at my smooth, level floor.

Assuming that all sounds reasonably sane I then had some follow up questions:

• Can I tile directly onto the ultraplan renovation or does it need cleaning/priming again?
• I originally planned to overboard the chipboard with some tile backer board but if the floor is already level/stable this seems like it might be redundant now. The ever increasing height of the floor is also a challenge.
• I saw something in the instructions about minimum depth over wood should be 3mm. Does this mean I need to go 3mm past my highest point even though the room is already theoretically level at that point? Seems like a waste of material and unnecessary extra height on the floor.

Any thoughts/tips/advice very welcome. Thanks!

 

[Dan]

Can't answer all the questions there but the minimum amount of levelling compound is because 1mm or 2mm doesn't leave enough product to hold its strength and it likely to crumble. So the minimum is there for that reason. So, on a concrete floor I'd be levelling the deeper bits but then simply make up the rest with a bit more tile adhesive as you tile.

Long plank tiles can bow, so make sure you use some sort of lash clips to hold them in place while the adhesive cures.

As for the woodchip, I'd actually remove and replace with something like aquaplanel or some load-bearing tile backer board.

The fact it would have been level when installed suggests it has weakened over time (it's not meant to be the finished floor with vinyl or something on, it wears and warps and whatnot).

So you may even find the big dip in the doorway could be a joist has slipped or lost its strength or something so that needs investigating too.

Don't wing it mate it looks like you've spent a fair bit overall so get the preparation sorted before you mix anything at all.

Not sure expanding foam should be relied on around any trap. It will be murder to cut through to rescue a leak years down the line. You want an access point to the trap to service it every few years or at least be able to get to it.

I think you need investigate the subfloor then get that floor level by other means (the joists then tile backer boards) and not just temporarily level it. As it will just sink more once even more weight is added. So there's an underlying problem there mate.

 

[bsc ceramics]

What dan said😄👍

 

[Dan]

It's rare I can contribute lol but that situation I have experience in I'm afraid 😨

 

[Stompfrog]

Thanks Dan.

Just to clarify, I was only going to use the expanding foam to do a small border on the chipboard around the outside of the waste hole to stop all the leveller pouring down into the ceiling below. I was going to remove 95% of it once the leveller had dried. I wasn't planning on putting it anywhere near the trap/pipework.

The house is fairly young (2008) and the joists are I-Beams that continue beyond far where I can see under built in wardrobes and other bedrooms/bathrooms. I don't really know what the old screeding is about but it appears to be just a thin smear that you can see though in several places. I don't think there was a major dip or anything.

The floor is pretty flat its just not level. There is a gradual slope from the window to the door rather than any dramatic drops in one place. The joists are running left to right. The floor feels solid to walk on and I can't see any evidence of movement (although I'm not too sure what I'd be looking for).

 

[Dan]

Foam; fair enough mate that makes sense.

Slope, if you can whip a board up and make sure the joists are solid and fixed to brickwork then perhaps it's something else but I'd imagine it was level when originally installed. Unless its an extension or something.

I think for the sake of 10mm I'd tile the floor flat but not try to get it perfectly level. If it's 13mm over 3m that's not that much per meter and could be gotten around by tiling the high end first and bringing it up say half the amount using the adhesive (sticking with the thickness range of whatever brand you end up with) and you'd find the 7mm isn't a problem really as long as the rest of the tiling is spot on.

 

[Dan]

These might be handy for the waste-hole.

https://www.amazon.co.uk/dp/B09FLD6RK4/ref=cm_sw_r_as_gl_apa_gl_i_HS1Q3HC7RV5R4H455AES?linkCode=ml2&tag=electricia068-21

Clamp a bit of wood to the edge maybe.

But if that's the high end you wouldn't be pouring there anyway and the adhesive is thicker so you wouldn't really lose it like that.

 

[Stompfrog]

There is a long board running along the right hand wall that is easy to unscrew and from that I can see where all the joists join the wall. I will check that after work, thanks.

I didn't actually know the floor wasn't flat until I put a spirit level on the shower tray.

Purely in an aesthetic sense, a subtly out-of-level floor doesn't really bother me. If there wasn't a shower tray involved I would probably just leave it as it is. Unfortunately gravity insists that I do find a way to level the shower tray, and once thats flat, having it gradually emerge out of the tiled floor along its length might look a bit wild. I like the idea of lessening the effect with extra adhesive though. 👍

I'm assuming the tray is pretty unforgiving when it comes to being off level. Although I don't remember having any problems with the old shower tray which was siliconed down to the same bit of floor.

Perhaps there is a way to shim the shower tray. The instructions say to stick it down with silicon and large portions of it are not in contact with the floor already.

 

[Stompfrog]

I lifted the board and had a look at where the first four joists join the wall. All have steel brackets sandwiched between two blocks and supported by the block on the row below. All the brackets are cemented in and I can't see anything that looks off/cracked/broken/wrong (not that I am an expert on construction by any means!).

I put a level on the joists and the third one seemed a little high. Perhaps it was built on a Friday afternoon.

 

[Dan]

It's been pointed up more at some point by the looks of the newer darker cement but doesn't look cracked so id guess somebody clocked a slope, checked, and just thought they'd at least lock it in again. If that was the case it's clearly been stuck the same for however long.

I'd even say there's more on the left and there is less new as it goes to the right there in the pics. So perhaps dropped flat at least (not one on it's own which may bounce). May have even had a bit of deflection (vertical movement) and they solidified it in the down position.

I'd be fine with that as long as it doesn't bounce at all.

I've just nipped maccies I'll try to answer your other questions but to be fair I've been out the game for a while so the product choice you might need a proper current tiler to guesstimate what will work.

 

[Dave]

The issue you are missing is you cannot just level on particle/chipboard. It isn’t stable enough. Needs over-boarding with hardibacker or similar.