Advice for New floor prep for tiling

Hi all,


i have finally bitten the bullet and dug up a failed screed floor in a kitchen which i need to get ready to tile.
I'm going to put 60cm x 60cm large format tiles down so floor has to be spot on, and it has to match level with adjacent room that will be part of expanded kitchen.
I want to ask for advice on the best type of screed to use i.e. Standard sand and cement 4:1 or some type of latex flowed screed.

Aside from that will i need to use a SLC and decoupling mat across the entire space to make absolutely sure of level uniform surface thats going to absorb any small movement?

Floor area is roughly 3m x 3m x 80 mm deep over a 150mm slab thats sound.

Advice appreciated.

Why did the previous screed fail?

Was it a S&C "screed" or a SLC?

Does the slab have an effective membrane?

Is the slab a one piece slab across old & new kitchen floors?

Hi Ree

The original screed was S&C, it failed because the mix was obviously not strong enough, or was too dry when laid. For a number of years it was covered by tiles, but since ripping those up, and putting SLC over to level, it has sat for a few months, and developed cracks.

So rather than tile over, and risk cracking the tiles, i dug it up.

The slab does have a DPM and its in good shape, no cracks etc.

The slab is on one side of the kitchen only separated by part of the original house 10" solid wall, effectively two rooms with joining wall removed. The other side of the kitchen is a 100 year old scullery slab that's not going anywhere.

I want to replace the removed screed to a level height and tile over the lot, placing a suitable decoupling membrane like rapid mat over the floor first.

so im wondering what is best, S&C or anhydrite flowed for flatness, speed and cost.

cheers

It appears that you have joins between the new slab and the old slab(s), esp. at the position of the now removed 10" wall?

How have you detailed these joins?

For an 80mm depth then a S&C screed will work, and be cheaper than SLC. But who will lay the screed?
Note that typically the kit FFL (tile) should flow into the next room(s) at the the same FFL height.

You must take advice from the Mfr's instructions for the mats.

I assume that the complete area is a shell - no app's or units.

Is the main house suspended floors? If so, is it cross ventilated?

Hi

The wall is still present to about 50mm below the FFL.

SO once the new S&C screed is put down i intend to put a SLC over everything then the matt, (per BAL) before tiling with SPF. The joins between the wall and the slabs will be covered plasterers fglass tape prior to the SLC.

The kitchen does have apps on one side, but these will be moved around once sufficient area is tiled and grouted to allow the rest to be finished.

AT the moment 50% is a shell, the other is still housing fitted units (to be discarded).

The house itself is suspended timber with dwarf walls with ventilation via missing bricks in the walls, and airbricks to the outside.

The kitchen (old and new) are solid.

The FFL will be consistant across the entire space, i.e. no level changes.

So, S&C is the best bet?