Newbie help

[gavin2.6]

Hey guys, Hope everyone is ok today.

Reason for my post is i am having a few issues with my kitchen floor tiles.

I had an uneven floor in my kitchen so put a concrete layer on it about 15mm then tiled over it.

90% of the fllor is spot on but in one area the concrete starting crumbling and the tiles wont stick to it.

I removed the concreate and redid it. 4-1 mix with cement and builder sand and some waterproofer/plasticiser in the water mixed to correct amount. Once dry i added some own brand b and q tile adhesive to the floor and stuck on my tiles. Next day the tile glue was rock hard around the edges but the tiles had not stuck. They come away without any force.

Another thing i have noticed is the concrete is not rock hard. Its sort of dusty and if i scrap it with my trowel i can make deep scores in it and the concrete just goes to dust.

Any ideas what i have messed up on would be welcome.

Thanks for reading all.

Cheers

Gav

[david campbell]

did you put an s.b.r slurry coat over the floor before laying the new concrete?
you say concrete!did you add any aggregate to the mix or is it cement and sand?
also you need to let the floor dry out(1mm thickness per day)
what type of adhesive are you using? tubbed or bagged?

[Diamond Pool Finishers]

you should have used all-in agg, not builders sand this is soft sand for making morta for laying bricks

[gavin2.6]

I had 2 bags of sand. one builders which is fine and another sharpe sand that has big chunks of stones etc in it. I guessed finer sand would make nice surface for tiles to sit on.

In terms of sealer. No used. Just let concrete (sand & cement mix) dry then chucked tile adhesive ontop. Am guessing that the oncrete has sucked the moisture from the tile glue and made it go funny?

Not used srb on top of the concrete floor. Just glue then tiles lol. They rest of it is so solid its not going anywhere. Its just the little bit near where the door is.

[david campbell]

you should have used the slurry coat before adding the mortar that you laid to even the floor up as it helps to stop it drying to quick and also removes any dust that would prevent the new mix adhering to the old,also there should have been aggregate or some kind of chip through your mix for strength!

as above you have mixed bricklaying mortar,probably best chip it up and start again

the 15mm layer will need 2 weeks to dry before tiling also

[nybor62]

imo, i would,nt have thought 15mm was thick enough , i would have thought a min 25 mm would be needed in order for it to work, if you have the right mix

[Dave]

15mm is to thin with a coarse sand mix... not enough thickness to bind and builders sand isn't strong enough..

You can wet fix the tiles but not recommended if you haven't done it before..

How big an area is it..?

[pjc]

you can screed down to 10mm with sbr but you need to know what you are doing not 15mm with soft sand latex might have been a better idea at that thickness dig it up and start again

[whitebeam]

A finer sharp sand, runafix ( who produce sbr) claim you can screed at 6mm with the right sand with their product.

[gavin2.6]

Thanks for the info guys.

The area that is affected is about 1xm2. The floor already had a solid concrete floor. The slab looks about a foot thick. The reason i only added 15mm thickness is down the the existing floor level. I could not add more height as it would mess up the level of the floor,cabinets etc. With the 15mm concrete i added everything lines up fine. It would mean ripping the whole kitchen out to take any height of the main slab.

The whole room is 20m2 and the bit thats 2m2 is just a little area ajoining the back door opening.

My only options are to remove my additional 15mm layer from the main slab in the effected area and re-lay with sharpe sand then tile or just attempt to get the tiles to stick the 15mm concrete piece i have in place via some sealent.

The 15mm piece i have added is solid just goes a little dusty if you rub it.

[mikethetile]

I would remove the tiles and screed you have laid and use a leveling compound such as fibreplan

with soft sand your floor will continue to break up anyway