How to level very uneven floor for tiling?

I need to level the floor in my kitchen in order to prepare it for tiling. It’s a concrete floor that originally had wooden floorboards nailed directly into it and under these was a layer of bitumen.

The floor is seriously off-level and bumpy – I’d say it’s out an average of roughly 12mm, with some places up to 20-25mm, and some places down to 7mm. There’s no underfloor heating though there is a 2 inch deep trench that’s 8inches wide which has 2 x 0.5 inch qualpex pipes with lagging running along it to feed rads.

The room is 3.5metre x 3.5 metre, has 3 walls (opens into a diner area at one end which will have solid wood flooring) and is completely bare as the walls have just been plastered and the kitchen will be ready for fitting once the floor is levelled. What’s the best way of getting it level enough to tile? Will the bitumen be a problem for binding, and if so, will scraping it overcome this?

There’s plenty of jobs I’ve taken on no bother but the problems I had last time I tried something like this it didn’t go perfectly (was laying a wooden floor over it and though it was ok it was far from perfect), so I need to figure out how to do it right. I’d actually be prepared to pay a few bob to get this job done but reckon it’d be hard to find someone at short notice.

Any tips on method, materials, or tools to use would be much appreciated.

have a look at this stuff.

[broken link removed]

Similar query here.
Leo

Thanks for the replies. Joe – that link to rsgroup.ie doesn’t seem to work – is it the right link?

I’ve looked into other threads on similar topics but this is a bigger job – levelling compound is only good up to 4mm I think, so I need to find some other way of sorting this out.

The thread above suggests using a thick bed adhesive to level up to 10mm. Any more than this and you'd be better off laying a ply base.
Leo

have to agree with leo - go for the plywood base - this will also sort out any potential problems with the trench holding the qualplex

If the floor is that bad I am assuming its an old floor and would have to wonder if there's any insulation under it? If theres no insulation I would take the opportunity to dig it out and do it properly. Tiles on a conrete slab with no insulation can be arctic.

Ardex K15 could be your solution. Mix with an aggregate. You will need to prime the substrate. It may be worthwhile contacting ardex as to which primer to use. They are in Damastown Ind. Estate - I think.

[broken link removed]


S.B.

Nice one Satan! That Ardex stuff sounds like it might be the exact product I am after - i.e. a levelling compound for more than 10mm. A plywood base isn't really suitable in this case.

Good point on the insulation, the tiles will be very cold. Will have to consider digging up and adding insulation, but time constraints may rule this out.

Thanks.

Make sure floor is clean of oil, dust and damp. Simply paint on some Ronofix, and while still tacky spread some semi-dry sand/cement (3:1) to deeper areas. Level as much as possible. Then, next day pour some self-levelling compound on and rub just once with a steel trowel.