Dodgy Concrete Floor

[toshki]

Hi Chaps, 1st post on here, hope you can help. I've just been to size up a job for a friend. Now I'm not a pro tiler by any stretch but have done a little bit and read this forum quite a bit, scouring for answers and best practice.

Anyway they've just got a new kitchen in and want the floor tiled. The problem is the concrete floor is a bit of a mess. There are several cracks and it is far from level, I've read all about self levelling compounds, which would be useful if it wasn't for the fact that one section of the concrete, maybe 0.5m2, actual moves when you stand on it! Whats the best course of action from here. Is it possible to ply over a concrete floor?

Other than running a mile from this what would the pros do, or would they run a mile too.

Thanks

[Dave]

Hello and welcome to tilers forums............

personally i would sort out the bit thats moves before going any further......

[CJ]

Floating concrete floor.............now there's a first.

Definately needs sorting before going Any further.

Sounds like a major pain in the arris




Oh..........and Hi

[toshki]

Thanks for the replies so far guys. So to confirm, trying to screw some ply over the whole floor is a ridiculous idea? What is the solution? digging it out and re-concreting??

[Dave]

I would yes........screwing ply is not ideal and won't stop it moving anyway......how big is the area that is moving..?..

[CJ]

Why or how is it moving..............well, thats wot I would want to know

[Dave]

Why or how is it moving..............well, thats wot I would want to know

could be a few things Cj...bad patch up job from a previous job or movement etc.....who knows ...

Maybe a pic of the area would help us...

[MrSpoon]

you say its a new kitchen? do you mean theyve had the kitchen extended and the new floor is all cracked/moving

[toshki]

2 cracks about 1metre long run off at right angles. If you stand on the corner where they meet it looks like the whole section 0.5m2 to 1m2 moves down (maybe 5mm). Almost like standing on the corner of a raised tile that isn't very well adhered to the substrate.

Of course my mate is looking for the most cost effective solution, hence the ply over the top of it.

[robbo]

Why or how is it moving..............well, thats wot I would want to know

Agree with cj , deffo wanna see why its moving before going any further...

[Dave]

How old is the floor/house....?.......some newish house have floating concrete floors where they pour concrete onto kingspan polystyrene sheets for insulation........this could have collapsed/crushed or not enough reinforcing etc...you won't know until you sort it out...

[toshki]

Its an old 1900's end of terrace house. The kitchen is in an extension off the back, not done recently. When I said new kithcen I just meant new units etc. Just trying to get my mate to send over a photo.

[whitebeam]

Is it a cement screed if so remove loose area only about 50mm thick

[Dave]

Just noticed toshki has put a pic in his album of the said floor.......

[toshki]

You found it, I was trying to figure out how to post it!. Yellow lines indicate cracks. When you stand where the arrow is that whole section moves 5mm up and down

[MrSpoon]

well i can say that those mustard and ketchup lines will have to be cleared up well otherwise the primer and adhesive wont be able to acheive good strong bond

[toshki]

Hopefully another pic here, complete with more mustard and ketchup!!

[whitebeam]

If it,s moving 5mm needs to come up and checking out

[Dave]

this one toshki....

[toshki]

yep, that's the other one, cheers Dave

[CJ]

Has it been OVER SCREEDED by any chance?????

Sounds like it has in the not to recent past.

Old floor possibly over screeded and old not prepared properly...........and new de-laminated from the old............hence the movement, its breaking up underneath??

[bigneil]

one way or another, it's gonna have to be sorted. if, as suggested ,is just a dodgy screed or top layer then you could give it a few exploratory thumps with your 'glaswegian screwdriver' to find out. If it is just a loose top layer you can get out the sds chisel drill.

[Spirit]

This really should have been fixed before the new kitchen was fitted. In a property of that age, there are many possibilities. One scenario that I have come across on quite a few occasions, including my house is that the floor can be only an inch or two of concrete laid straight on top of the soil. If that is the case, the only correct solution is to dig it out and construct a proper floor. (50mm screed on 50mm insulation on 100mm concrete on 1000g membrane on 150mm blinded hardcore.)

Whatever the cause, this will have to be repaired properly before tiling.