Patching a concrete floor

[DrPhill]

Hi all,

We have (at long last) started on the bathroom. We have a number of 'opportunities to learn'. First off is how to patch the concrete floor.

The bathroom was originally three areas: a spur off the hall (quarry tiles) a toilet room (wood block) and a bathroom (woodblock). The main area of woodblock in the bathroom was ripped up and replaced with concrete of some kind, level with the quarry tiles. The dividing wall was removed and finished level with the quarry tiles. The woodblock was left around the toilet(apart from a crude concrete plinth for the pan) and under the bath.
The floor was then covered in cork tiles, followed by lino. Guess what? The woodblock around the toilet was rotten.

So to remedy, we are going to level the floor with hard stuff. So my first 'learning opportunity' is to fill the space left by removing the woodblock around the toilet. The space is about 28" x 56" x three quarters deep. The base of the area is concrete of some kind with some tar residue from the wood blocks.

What would be the easiest/cheapest way to fill this? My first guess is rough concrete (or similar) followed by floor leveling compound.
Ideally the technique I learn would be used for the area under the bath when we rip that out. Maybe there is something that can fill the entire depth in one go and still be smooth on the top? Or would that be too ambitious?

I have done crude concrete work outside where finish is not as important, I have levels and such.

Oh, and I am doing this piecemeal as this is our main bathroom - we want to keep it usable (toilet & sink anyway) for as long as possible. When we have done as much of the unskilled work as we can we will get the professionals (electrician, plumber, tiler) in.

Any advice would be welcome - I do not want to cause extra work remedying my own mistakes.

 

[stuartpaul]

Phill,

You can get self levelling compound that will do that depth, - I looked into it recently for one of our duff floors e.g. https://www.screwfix.com/p/mapei-ultrap ... 25kg/4959f

That size might work out expensive but I would have thought it a better option than a DIY concrete one as this stuff is designed to be used this way. Chance of failure in the future if your own 'stuff' breaks up could be quite high for that thickness?

Does of course depend what final finish you're going to use.

HTH

 

[DrPhill]

Thanks StuartPaul, I did not realise that self levelling compound could be that thick - the YouTube videos concentrate on thinner skims.

With no Screwfix nearby I might have to go to Jewson, but they do this: https://www.netweber.co.uk/tile-fixing- ... level.html which says up to 30mm. 0.75" is about 18mm so I may try that route.

 

[Homers double]

You can bulk out self levelling compound with sharp sand, works a treat with deeper areas.

 

[DrPhill]

You can bulk out self levelling compound with sharp sand, works a treat with deeper areas.

One of the products offered by Jewson even recommends that you do so for deep areas. I lack the confidence to do so it is going to be difficult enough to mix up the right amount to fill the odd-shaped gap

 

[novocaine]

you can chuck in some poly fibre to add strength too which for that depth isn't a bad idea.

 

[RobinBHM]

If the area that is lower is quite flat, Im wondering if you could lay a 6mm and a 12mm hardieboard to bring the level up. Use self level on the bath area and anywhere else that needs it.

I would then recommend using a ditra mat over the whole area.

Im not saying itll work just an alternative idea......

using self level that thick the first time might be a challenge

 

[DrPhill]

Just done the job. What a weird way to work. Mix it, pour it, let it level itself (I checked first that the edges of the hole were level). A bit expensive, and 40kg only just filled the hole. It might need a final skim before the flooring is laid, but for now it worked a treat and at least that part of the job is done.

If the area that is lower is quite flat, Im wondering if you could lay a 6mm and a 12mm hardieboard to bring the level up. Use self level on the bath area and anywhere else that needs it.

What is that? hardieboard? I could do with some kind of filler for where the bath is - the entire under bath is woodblock to be removed. Something cheaper to make up the bulk might be a very good idea.

 

[stuartpaul]

Phill,

Hardiboard is a trade name for cement backer board, other makes are available!

If you've got a gap under the bath does it matter? Just use some batten to raise the bath if necessary.

 

[DrPhill]

If you've got a gap under the bath does it matter? Just use some batten to raise the bath if necessary.

The gap is under the bath where it is, not where it will be - if that makes sense. The new bath will be at 90 degrees to the old one, and likely will be one of those free-standing sorts. So the floor needs to be 'made up'. Good thought though.

The cement backer board may be a good idea (dependent on availability, cuttability, affordability) or bulking out the floor leveller with sharp sand. Even if I just use sand in the initial layers and finish with unadulterated leveller that could save some cost.

I have to say that I found the levelling compound easy to use. Now If I could turn the house on its side I could plaster the walls nicely too.