Pre-tiling floor prep advice

Idioteque

Hi,

I removed the floor tiles from an under-stairs toilet. Given there are some divots in the floor I was going to pour some self-levelling compound to even out the floor before tiling. However, there's an alcove section of the floor that used to contain a doorway and you can see some white plastic on it (I'm guessing builders put that there instead of the black DPM you can see on the sides where the wall was cut out for the door). Also, there's an exposed waste pipe which I think is unused as I know where the existing sink/basin waste exited and it wasn't through that pipe. The pipe has loose material around it.

My question is what should I do with the alcove section to make it able to take the self-levelling compound? (Given the plastic and loose material surrounding the waste pipe). The previous tiles just had the adhesive directly onto that plastic pipe.

Also, once sorted, should the floor be primed with SBR or similar before applying the SLC?

Any advice is appreciated!

paul321123

Not really sure regarding your question but I have removed tiles in my kitchen and am left with screen on the floor which makes it very uneven, I need to remove this screed but not sure what the best way to go about this, I have been scrapping this off but that is very slow and not really getting it all off, how did you remove the screen from your floor, I need to remove this before ant self leveling compint is applied,

GreeBo

https://www.boards.ie/discussion/comment/122503522#Comment_122503522

Why do you need to remove it before applying the self levelling? Also whats the plan for the finished floor?

The floor doesnt have to be perfect to tile over, the tile adhesive can go over existing dried adhesive, as long as its well adhered to the floor. I am assuming it is if you are having trouble removing it!

The only option is a spade bit with an SDS drill on hammer action only. Its a curse of a job and will share the bejesus out of everyone and everything in the house and any connected house. If its not on concrete (e.g. suspended wooden floor) then its easier to replace the subfloor itself.

GreeBo

I wouldn't worry about getting a smooth surface for tiling over, the tile adhesive will fill any gaps.

As for the DPM, it cant have been doing much when it was a doorway and less so when someone lashed some plastic over it, so I wouldnt worry about that either.

You could check for damp by taping a piece of plastic to the floor in this area (tape all 4 sides) leave it for a couple of days and then take it up, if its wet underneath then you might have a damp problem, but from the looks of it its all pretty dry.

If you wanted you could pour a self levelling screed, tank the floor and then tile over, but for a concrete floor I think its overkill. Also you would want to the confident that the existing floor is level, otherwise your screed is going to make it level and you might end up with a mess or a step up into the doorway for example!

paul321123

Thanks for the replys, just going to tile over it again, was told that the floor needed to be fairly level, is that not the case? Have tiles up and am using a scraper chisel to remove anything that left, bitch of a job but am nearly finished.

Bawnmore

I'm just after doing something similar in our bathroom - I'm not in the industry, just someone doing their own bathroom, so more than open to criticism, but here's what I did:

1. Took up the old tiles with an SDS with a spade bit.
2. We were left with a lot of adhesive and in quite varying heights so relying on self levelling only would have had to raise the floor higher than we wanted.
3. I tried taking down any of the higher bits with the same SDS/spade bit but it was taking forever.
4. Ended up buying an angle grinder cup wheel (this guy) to remove the remainder of the adhesive.
5. Original intention was to take it all back to concrete, but it kicks up a LOT of dust. As we were self levelling, I decided to take down the highest peaks with this before self levelling.
6. Poured self levelling compound yesterday. There's still a few small peeks, so going to knock these back when it's fully dry and we're good to go.

In our situation, I reckon if I just went straight to self levelling, we would have had to raise the floor too much.

The only problem with not levelling your floor before tiling is that you will use a hell of a lot of tile cement. The morter type tile cement is not cheap for the good stuff and the premixed buckets are not great for floors.

Time spent with your SDS spade bit will be well worth it despite the mess and effort.

GreeBo

https://www.boards.ie/discussion/comment/122515175#Comment_122515175

A tiled floor needs to be flat, not level!

One level floor might mean that you end up with a 20mm step at the door threshold.

If you are going to level the floor then you would want to level the entire floor of the house to avoid steps. If you wont gets any steps then the floor is probably level enough to begin with!