The best way to upgrade an existing solid floor to modern standards is to excavate the existing floor to allow for the construction of a new solid floor.
Fill floor area with compacted hardcore and sand blinding to correct depths and height. Lay DPM over sand blinding then pour and level concrete to specified depth including any required steel reinforcement.
A 30mm insulation upstand should be installed around the perimeter of the floor and continued up the wall to meet the bottom of the plasterboard. Using this method will reduce the Ψ value achieved at this junction.
Lay 120mm Insulation on top of the concrete slab with all joints taped and sealed, finished with a layer of screed on a Vapour Control Layer. This method will reduce compression of the insulation which can occur when the insulation is placed under the concrete slab and allows for easy installation of underfloor heating.
Excavation should be carried out carefully in case there any service pipes or cables running under the existing floor area.
Damp Proof Membrane should be continuous with the wall Damp Proof Couse.
Hardcore should be compacted in stages no more than 75mm deep.
The level of the floor should be carefully calculated during excavation to ensure the finish is at the correct height below the doorway thresholds.
For each Ground Source Heat Pump installation we recommend that you undertake an independent assessment of the site to ensure your design is optimised to suit the ground conditions and building.