Rising damp through flooring screed

It really depends on the condition of the concrete. If not in good condition it's usually best to dig it up and redo properly with a DPM. This may also be the cheapest option if a small area. However, it's not the only option. A Liquid Epoxy Damp Proof Membrane (DPM) is often used as a remedial solution where an existing DPM has failed or was never installed. The epoxy DPM comes as a two-component system. It is low odour, solvent free, and most importantly deals with constant low levels of moisture in concrete floors. There are a number of benefits to using a liquid epoxy DPM: An epoxy liquid membrane is applied to the floor itself and creates an impermeable layer meaning that water stays in the concrete slab. This is different from plastic DPMs that sit above the concrete slab and can potentially allow water to pass through to the surface of the concrete. This becomes a problem when the surface water moves to the edges of the DPM and transfers up to the floor covering, skirting boards and wall finishes. In the case of existing concrete floors in factories, commercial spaces and offices, epoxy floor coatings can also be used for its visual impact with its high shine finish and range of colours as well as acting as a DPM for those wanting to achieve a decorative finish. Epoxy membranes can be applied directly to damp floors meaning you don’t have to remove the old concrete screed which is an extremely expensive, dirty and time-consuming process. You also don’t have to wait for the floor to dry before installing the damp proof layer, saving you time.

Old screed would need to be lifted back to the concrete then left to air for a day or 2 then you'd need to apply a 2 part dpm (F ball 77 then rescreed with ardex NA .....hope this helps ,we're booked until June so we can't fix unfortunately