I have a 1920s house with cavity walls and slate DPC. As part of my extension, I have had a suspended timber floor lowered so that I can use thick insulation board below electric UFH and thick tiles whilst maintaining the same, final floor level. One end of the new, treated joists are now mortared into the internal sleeper wall and the other ends are into galvanised shoes mortared into the inner leaf of the outer wall. All the joist ends are now below DPC level. Should I be worried about damp getting into the new joists?