Advice on screeds needed

[Phoeni1266]

I'm about to start leveling an uneven floor in prep for stick down LVT.
Floor is a mix of wooden floorboards in one room, a concrete strip between that room and the kitchen (we knocked out a wall) and a screed on top of plastic tiles on top of floorboards in the kitchen. We've had the tiles tested and no asbestos.
I really don't want to take up the tiles/old screed so was considering levelling the worst of the irregularities with a concrete screed, laying 9mm ply then feather screeding the joints.
Two questions: is this likely to end in a poor finish and, if not, what products are best for each of the two screeds?
Sorry for the long post.

 

[dazlight]

You need to uplift all the tiles.
Plywood the wood sections with 6mm flooring grade plywood .
How old is the sub floor? Does it have a visqueen Dpm under it

 

[Phoeni1266]

You need to uplift all the tiles.
Plywood the wood sections with 6mm flooring grade plywood .
How old is the sub floor? Does it have a visqueen Dpm under it

Bugger! That not what I wanted to hear.
The house is 1950s and the boards are original. I doubt there's a DPM under the wood.

 

[Phoeni1266]

Or did you mean under the kitchen screed? There isn't one under that

 

[dazlight]

Then you will need a liquid Dpm doing.
So my order would be -
Plywood wood areas
Self level with a moisture tolerant company like ardex Na to the level of the plywood
Apply a epoxy Dpm to the screed
Prime & Self level ( smoothing compound ) to the whole area at 5mm

 

[Phoeni1266]

Thanks very much

 

[Phoeni1266]

Can you recommend a primer?

 

[dazlight]

Loads to pick from.
I’d use the same as the screed you buy.
Ardex
Mapei
Fball
Uzin
Bostik
Tilemaster

 

[Phoeni1266]

Cheers

 

[Phoeni1266]

I'm about ready to start this project.
When I ply the floorboards do I need to leave an expansion gap around the edges?
It's just that, on one wall there's a steel perimeter radiator which doubles up as skirting. It's not connected to the heating system but it would be difficult to trim anything if the bottom of it so I can't get the flooring under it.