Help!: Tiling new extension and existing kitchen

[BroughtyTiler]

Hi All - Long and complicated question coming up....

I have been asked to estimate a job to tile a new extension (42m2) and back onto an existing kitchen floor (8m2) without a step in between.

The extension now has a concrete base, onto which he has 50mm insulation boards, under tile heating then 12mm porcelain tile to be put down. The existing floor in the kitchen is tongue and groove floorboards over joists which he wanted me to tile straight onto - NOT!

From the concrete base, there would already be a 5mm height difference from the new fully tiled extension height to the tiled kitchen floor if I did tile straight onto the floorboards (Which I refuse to do).

He doesn't have much room between the top of his washing machine and dishwasher to the under side of the worktop - about 12mm-ish so I can't use 12 or even 9mm ply to overboard the kitchen floor.

I have suggested using 6mm Hardiebacker cement board to overboard the kitchen floor prior to tiling, which he has now accepted - But this brings me onto the real problem.

Working back from the new height of the finished kitchen floor, I would now have approximately 11mm difference between the kitchen floor and the extension floor. So.....

What would you do to bring the extension floor (42m2) up to the height of the kitchen floor??? - At a rough estimate, I would need approximately 39 bags of 20kg self levelling compound to do this :-(

Also, what would I need to put down at the interface between the two flooring areas - I'm thinking a de-coupling mat.

Cheers for any help :-)

[peckers]

as you are putting 6mm hardi on to the old wooden floor you stick this down with adhesive so you could add a couple off mill to the height you have come too. then you can fix down to the concrete new floor 12mm hardi, if you use the same depth trowel for the addy then you are a millimeter difference which im sure you could loose in the addy!
as to where the two different substrates meet you will need to put in an expansion joint between them and carry this threw to the tile surface.

[david campbell]

can't beat the above answer

[aph257]

couldn't put it better Peckers.

[doug boardley]

what type of UFH is it?

[Daz]

You deffo have to carry a flexible expansion joint to the surface where the two differing substrates meet.

What size are the tiles?
If not too large and you are not doing a brickbond pattern then you may be able to taper the floor with a floor smoothing compound so that it will look fine over the large area without having to use so much slc.

Just a thought, but Steve (Peckers) has really hit the nail on it's head .

[Daz]

Just re-read your post.

If it is electric UFH and you are doing the install, can you increase the thickness of the insulation boards, rather than add 12mm Hardie which can't be screwed on top of electric UFH?

[doug boardley]

if it's a heat mat or loose cable you'll have to lay it top of HBB tho' ( so you don't screw through it) and then slc

[doug boardley]

Just re-read your post.

If it is electric UFH and you are doing the install, can you increase the thickness of the insulation boards, rather than add 12mm Hardie which can't be screwed on top of electric UFH?

that's why I was asking Daz

[peckers]

I took it to be wet under floor heating in the screed with 50mm insulation could be wroung tho, perhaps broughtytiler will confirm if it is electric cable mat then could put 3mm slc down then 6mm hardi then heating matt then 3mm slc on top

[BroughtyTiler]

Hi guys - thanks for your replies so far...
Sorry for my omission, it is electric cable UTH
He has four sizes of tiles to go in a pattern name that I can't remember at the moment??

[Ken Bruty]

Hi guys - thanks for your replies so far...
Sorry for my omission, it is electric cable UTH
He has four sizes of tiles to go in a pattern name that I can't remember at the moment??

Could be Roman or Bella Opus Bt.