Hi all.

I would like some advice. I've laid 100mm concrete over dpm/Kingspan on half-basement barn conversion. The internal wall is quite rustic, rough sandstone, lime mortared, and corbels out slightly at the bottom. I ran a perimeter upstand of 40mm eps around the edge to create a bit of insulation from the cold external wall, and to keep the concrete from the lime mortar/sandstone. This now contains the concrete and will imminently contain the UFH and screed. Any suggestions for filling the up-to-100mm gap left at the back? The wall will inevitably have some moisture in it due to external levels and I wanted something that would let it breath/drain, while filling the void.

Sand? Pea gravel? Polystyrene beads? Damp mix of lime/sand? Any suggestions much appreciated.

Roger

Thanks Biff.

I know, limecrete or somesuch preferable but subfloor moist so DPM down and limited budget, hence concrete.

Is there merit though in anything with good thermal properties to fill the gap? The void is between the external walls and the DPM, which laps up behind the EPS. (All to be topped off with flags pointed in lime mortar).

Are those clay granules robust or will they turn to mush if moisteure gets in? Maybe gravel's the best bet.