I'm laying engineered wood flooring over concrete subfloor, 20 years old, using 7mm underlay boards & d/p membrane. Room size 5.5m x 3.5m.
Trouble is, the floor has a slight "domed" profile; the edges are about 1cm lower than the centre. For a DIY bloke like me, what's the simplest product for levelling the floor off.
Advice much appreciated