We recommend FL330 Fine Flow Smooth Levelling Compound or FL307 Fast Setting Flexible Levelling Compound because of their higher compressive strength. 

All our underlayments can be bulked out with aggregate to enable them to be applied to greater thickness. Check the relevant data sheets for this information.

Yes, you should always remove as much residue as possible, paying particular attention to any friable residue. Both FL390 and FL301 can be applied directly over old adhesive residues without priming in most situations. Surfaces should always be sound and free of any contaminants that may inhibit adhesion of the primer system, moisture control system or smoothing compound.

No, the expansion joint should be taken through to the floor finish and a suitable expansion joint / cover fitted. 

No, most smoothing compounds are polymer modified and have a controlled level of absorbency.

Old buildings pose the most risk however new buildings still remain susceptible to moisture, as the drying time of a new sand/cement screed is estimated to be 1mm per day up to a thickness of 50mm. A 150mm thick concrete subfloor can take up to a year to dry out naturally. Therefore, to ensure that a concrete subfloor is sufficiently dry to receive a floorcovering, all projects should be tested for moisture.

A recently-installed concrete screed is likely to contain a large amount of residual construction moisture, which can potentially cause complete floor failure if no waterproof surface membrane is in place to stop it rising up to the level of floorcoverings. You will need to leave at least seven days but check with the subfloor installer, as different products have varying drying times.