laying a tile floor on a new concrete slab

built a new extension with a concrete slab floor(insulation underneath). Room has a set of french doors and a back door. Now about to lay tiles but want to know how to bridge the 100mm cavity which exists at the french doors and back door. Don't want to compromise dpc.

Covered recently...

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this depends on the height of the blockwork but you could in fill with concrete.cover with strips of slate or use some insulation in cavity.simon the builder

I am not sure why you are left with an exposed cavity, under normal circumstances the cavity would have been closed off with the frame to the doors. Albeit in this instance you have a 100mm cavity but the same principal applies and you would create a deep door lining for the entrance doors and then fix the door frames to the lining material. You would finish the lining detail in a bullnose and have it slightly proud of the plaster finish to the walls.

Just a point - the threshold of the internal and external brickwork should finish at the same height.

Regards

threshold internal and external finish at same height. I've set the french pvc doors forward to enable the outward opening doors to swing right back. Frame about 70mm thick so no cover over the cavity whatsoever. If I use a concret fill with insulation surely this will form a bridge for any moisture to traverse the cavity. However will do this with some dpm. thanks to both you guys for the replies.