Fked floor in kitchen... Help

[berty3000]

Hi all,

Me again. Problem #3,678 in this ongoing renovation.

I'm getting the kitchen replaced in a few weeks. Part of the deal is that I'm removing all the units and existing tiles/adhesive on the floor. The tiling in there looks as though it was done in the late 80s and replaced quarry tiles. The fitter is going to make good the floor and use self leveler to get it right before putting new tiles down, then fit the units and so on.

The floor is obviously uneven as they have been in the rest of the house. They either used crap concrete or didn't compact the ground properly when they built the house, which is an early 60s bungalow. None of the tiles in the room are broken and they've been in place for probably 35 years. No obvious evidence of damp emerging from the ground, up walls, etc. That's just some context.

Anyway, under where the cooker was, there were no tiles laid, but the back of it was sat on some old quarry tiles left there loose. When I removed these quarry tiles I found the underlying material, which I thought was the concrete base, to be cracked in several places along the wall. As if there has been settlement. You can see the imprint of the quarry tile bottoms in this material, which is over an inch thick.

I have pulled these broken chunks out and then found what looks like a concrete slab below... the broken pieces were up against, and above, the DPC of the inner cavity wall...

So...

- Is this material that the quarry tiles were on some kind of thick, cementy screed that was poured over the concrete base when house was built? I wonder why it was so thick and why they went above the DPC?

- the 1980s tiles and their adhesive are on top of whatever it is that the quarry tiles were laid on.

- so, when I'm removing all these tiles and the adhesive with a hammer drill, how far down do I need to go? I'm basically just wanting to tee up the kitchen fitter to put down his primer and latex self leveller... do I need to remove the tiles, and their adhesive, and the cementy thick screed stuff that the quarry tiles were on - OR - can I just leave stable and solid material in situ? So where those broken off pieces have been removed, put mortar in there and then screed over the rest?

Thanks for any thoughts and help.

 

[23vc]

The screed would have been poured to the finished floor level to suit door thresholds etc. No reason to remove it unless it’s knackered and it can be patched up with a concrete/screed mix.
Fwiw I’ve laid big porcelain tiles over (solid) 60s quarry tiles with the right primer and all good. I’d check with the tiler as to what they’re expecting/prepared to tile over

 

[berty3000]

The screed would have been poured to the finished floor level to suit door thresholds etc. No reason to remove it unless it’s knackered and it can be patched up with a concrete/screed mix.
Fwiw I’ve laid big porcelain tiles over (solid) 60s quarry tiles with the right primer and all good. I’d check with the tiler as to what they’re expecting/prepared to tile over

Thanks 23.

Yeah, that makes sense.

That's good you were able to tile over the quarries. I assumed they might have done that here but when I've seen the 1980s tiles and their adhesive in cross section, it looks as though they removed them. Perhaps the surface would've been too high in this case.

So hopefully the old screed will stay largely intact when I'm taking out the tiles and adhesive then prime, self level over that. Presumably ok of chunks come out of it as long as it is intact overall?

Would screeding over the tile adhesive work if it seems to be solid? Just thinking it might be best to leave a solid base in place as much as possible rather than create problems...

 

[Deluks]

Do you know if there's a dpm under all that?
Are you not tempted to dig it out and lay some insulation?

 

[23vc]

Thanks 23.

Yeah, that makes sense.

That's good you were able to tile over the quarries. I assumed they might have done that here but when I've seen the 1980s tiles and their adhesive in cross section, it looks as though they removed them. Perhaps the surface would've been too high in this case.

So hopefully the old screed will stay largely intact when I'm taking out the tiles and adhesive then prime, self level over that. Presumably ok of chunks come out of it as long as it is intact overall?

Would screeding over the tile adhesive work if it seems to be solid? Just thinking it might be best to leave a solid base in place as much as possible rather than create problems...

Yes you can screed (whether traditional sand and cement or latex/self levelling stuff ) over old adhesive with the right prep/priming
You can patch chunks of missing screed. I tend to paint it with that blackjack sealer stuff first if there’s any possibility of damp

 

[berty3000]

Do you know if there's a dpm under all that?
Are you not tempted to dig it out and lay some insulation?

No DPM. I think the quarry tiles were the DPM.

I only have limited time before kitchen fitter starts and removing the concrete sub base is out of the question.

 

[berty3000]

Yes you can screed (whether traditional sand and cement or latex/self levelling stuff ) over old adhesive with the right prep/priming
You can patch chunks of missing screed. I tend to paint it with that blackjack sealer stuff first if there’s any possibility of damp

I'm not aware of any damp in there. No smells, no mould (apart from on the wall behind some lower units, but that is more to do with absence of ventilation over decades, there's no blown or swelling plaster work suggesting "rising damp"), no blown tiles, no rotten cupboard carcuses at ground level...

Ok, what's the cheapest and easiest way to get some effective damp proofing in that won't cause moisture to migrate up walls or such? Bearing in mind that, as there doesn't seem to be a damp problem now without a DPM, any humidity that does come through the floors just goes into the air and I ensure good ventilation. In other words, the floor breathes. I don't want to cause a problem that doesn't currently exist. Are liquid DPMs prone to blowing if there's a build up of moisture?

Could:

- Remove all 1980s tiles and as much of the adhesive as possible whilst trying to keep the pre existing screed stable and intact.

- fill large holes in the screed where chunks have been removed with sand/cement mortar? I assume this needs to be fully dry before primer can go on?

- my assumption was then to use primer, let that dry and then apply latex self leveller before new tiles go on. Where does the black jack or other liquid DPM fit into the equation?

 

[23vc]

the blackjack is just something I use out of habit, if I’m patching bits of screed. Yep, your plan sounds good. Anything you’re doing to prep for tiling shouldn’t really involve anything to do with dpm/dpc unless you’re digging down, which you shouldn’t really need to unless you go for the insulation plan mentioned above.

 

[berty3000]

Hi chaps,

Progress has been made. Tiles and adhesive removed (what a lovely job that was!) and you can see on the photos that the original concrete screed that the old quarry tiles had been on is mostly intact and solid. It is now heavily pitted and cratered though, probably 30mm or more in places, and there are the bigger holes in one area where it had broken up and was removed to reveal the concrete slab below.

I just want to check with the brains on here that I'm proceeding correctly whilst there's still opportunity to pursue different routes.

As mentioned previously, the 1980s tiles that have now been removed had not blown to my knowledge and showed no signs of stains or damp. The exposed screed has no damp patches on it, although one or two small areas looked a little darker when the tiles first came up. No signs of blown plaster on walls even though it goes down to the floor in places. All that said, there is no DPM. It is a concrete slab, 30mm or so of cement screed, and what had been quarry tiles (later replaced by 1980s tiles).

Should I put a liquid DPM over the cratered screed before self levelling? My only concern is that it might introduce problems I don't currently have, e.g. damp migrating up walls or some other factor I have not foreseen having never used such products. On the other hand, if it is a no brainer then I ought to take this opportunity whilst I can and before new tiles, kitchen and everything goes in...

Other option is to assume no significant damp issues, fill significant holes with sand/cement mortar (4 or 5 : 1), let that dry, put primer across the whole floor, then put down the self leveller, then tile over the top.

Thoughts?

 

[Mr Chibs]

How much depth have you got from the moon surface concrete to final floor covering?

 

[berty3000]

How much depth have you got from the moon surface concrete to final floor covering?

From moon surface old screed to final floor level... mm... unclear because the moon surface has numerous craters in it. Taking the highest point of that layer, plus the previous tile adhesive and tiles which are to be replaced, then isn't much to play with really. Although the removed tile adhesive might have been built up thick in places, so could be thinner this time. It's a good question... how thick is liquid DPM?

 

[Mr Chibs]

Liquid DPM is very thin... I was wondering if you could sneak in some insulation and screed. But the answer over is no to that.

If there was no damp previously, and your are re-tiling then I'd use self levelling to get the floor flat, then normal adhesive and tile.
I've never used liquid DPM and tile adhesive on top, it might be a question to technical department of the product you are using.

You might be able to use a decoupling mat instead, something like DITRA. You use tile adhesive to glue this the self levelled floor, then use adhesive again to tile the the mat, theory is if there is any movement, the tiles stay put.

DITRA mat is around 3mm thick and like a plastic roll, with indentations and a kind of hessian top.
I used it under my stone tiles for a floor with wet UFH.

***Should have said, due to it being plastic, it will act a bit like a DPM.

 

[berty3000]

For filling the deeper craters and holes before self levelling what mix should I use? 4:1 or 5:1? Is there merit in adding some SBR to help it stick? (If so, how much?)