I've just been to quote a floor job for a customer which is on two different levels, the majority of the floor is floorboards overlaid with 18mm ply covering 11.5m2. Then there is a further 5.5m2 which is concrete. This means to get the floor level i need to bring the concrete up 18mm .
Is there even a levelling compound that goes that thick, also how do i work out how much to use/buy. Is there a different way you guys would go to get around this. Would it be better to use cement boards fixed with addy then levelling compound on that like underfloor heating?
The tiles i'm fixing are slate. Any advice would be great, cheers.

You could use boards, but to be honest I think id prob just use slc as I think it would be cheater. I dont know what manufacturer you use, but most will do a compound that will take 18mm. As for how much you need, just go in to your supplier and say that you need enough slc to cover 5.5m at 18mm. They will point you in the right direction.

average bag will cover 3mm at 5m2 per bag so on that basis 6 bags of slc, you could always screw 18mm ply to the concrete, there is slc that goes that thick but cant mind the name of it,

andy

Originally Posted by Dylante

You could use boards, but to be honest I think id prob just use slc as I think it would be cheater. I dont know what manufacturer you use, but most will do a compound that will take 18mm. As for how much you need, just go in to your supplier and say that you need enough slc to cover 5.5m at 18mm. They will point you in the right direction.

5.5m at 18mm of slc would not be cheaper than 2 sheets of 18mm tops 40 quid for the wood and screws from timber merchant

andy

Mapei Ultraplan Maxi 3-30mm
An ultra-fast hardening, water-mixed truly
self-levelling & smoothing compound for
thicknesses of 3-30mm.
Where to use:
For levelling differences in thickness from
3 to 30mm on new/existing substrates.
Internally it can be used over concrete slabs,
cement, anhydrite, terrazzo, ceramic,
underfloor heating and natural stone, where
an excellent resistance to loads and traffic is
required.
All subfloors, prior to application, require priming.
Anhydrite screeds must have the laitance
removed.
Technical details
Colour: Grey
Consistency: Fine powder
Non-flammable
Application: From +5oC to +30oC
Application by: Trowel or pump
Light foot traffic: 3 hours
Setting time: 60-90 mins
Bonded floor covering: After 2 days
depending on thickness.
Storage: At least 12 months.
Consumption:
Approx. 6m2 at 3mm thickness
Packaging: 25kg
Mix with: 5-5.5 litres of water


Soo you would need about 6 x 25kg bags

I wouldnt use ply, backer boards or slc.

That read wrong.
I would not use Ply.
Id only use backer boards or SLC

There's a single part product called maxit 4310 that goes up to 50mm don't forget you will need a movement joint where the 2 different backgrounds meet!

slc that can be used with a fine aggregate mate!

there are some that dont require an aggregate possibly topcem pronto by Mapei (not 100% sure though) give Mapei or Ardex a call and they will recomend something mate.

You can pick up fine grano chippings from some good builder merchants