Screeding over bitumen residue on concrete floor

[Karl2016]

Good afternoon everybody,

I have recently purchased a house with old asbestos floor tiles. I am having these removed after being convinced by others to screed over - luckily only one bedroom and hallway was completed. The screeding/latex has laminated (like puff pastry) and is breaking up. I have approximately 50m2 of floor (3 bedrooms and hallway).

The questions I have are:

1. Is a latex screed the best option? My initial thoughts were to do one level of Ardex NA, then Ardex DPM-1c and then a final 3mm layer of Ardex NA.
2. I'm not too sure if the existing floor slab has any DPM. Would putting the Ardex DPM-1c cause the subfloor to condensate or any other damp problems?
3. The existing concrete floors are irregular through poor workmanship and/or consolidation. A structural engineer who viewed the property, says any previous movement happened along time ago and that the floors are not moving. The floor in one bedroom is -40mm from top in one corner of the bedroom (no more than 1m2). Can I make this up in latex, even though the manufactures recommendations are max 30mm?
4. If I have to joint the Ardex, say in the 1m2 mentioned above, is it better to have overlapping feather joints or a straight joint?

I would really appreciate the help.

Cheers,

Karl

 

[dazlight]

Done that System lots of times.
NA, DPM1c , NA
Works great. You can build up the levels with NA. Just do more coats.

 

[Karl2016]

Cheers, thanks for reaffirming my thoughts. How long can I work the NA? Does the material become harder to work when the aggregate is added?
With the DPM, do you first work it into the gap below the plaster and then just spread it normally?

 

[dazlight]

You want to keep the NA cool as warmer it is the quicker it sets. It goes off quicker with granno in.
Yes dpm to wall mate. , trowel on then roll it as well.