Hi All

The recent discussions talking about fililng voids with polystyrene, got me thinking about our build and got a question that I'm hoping you can help me with. Our house is 1930's solid pebbled dashed construction with a suspended timber ground floor. I assume this as there are metal ventilation grill on a couple of the external walls below the floor level.

However, the kitchen floor is at the same level as the other floors but is terracotta tiled and a couple of these are loss and underneath is what looks like solid concrete, this floor is really cold in winter which makes me think it's solid. The hall way is exposed floorboards but at the junction between the kitchen and wall the concrete seems to continue under the floorboards. But one of the external vents would be under the hallway.

We are planning a substantial extension and internal remodelling of existing house, moving stairs and upstairs bathroom to get an addition bedroom, updating electrics and plumbing and installing underfloor heating.

So question is:

Extension will have solid floor, not sure if I go for something like Viking Houses passive slab or have no insulation but extend external insulation down a metre or so below ground level. If we want to have a solid floor in the existing house is it possible to remove existing floor, dig out a bit to install insulation (or again just extend external insulation down a metre) and fill with concrete/screed and have underfloor heating under tiles.

Hi Tony

Sorry maybe not totally clear, existing house will be externally insulated and re-rendered.

Query was more regarding do I have to try and somehow tie the DPM in the walls (what did they use in the 1930's) to a new one if I fill the void?

Sorry for not being clear

Basically if I fill an existing ventilated void to get a solid floor with a bit of thermal mass for UFH, what do I have to worry about.

Any damp would perviously have been removed as the void is ventilated to the outside.

If I fill the void what will happen to that damp now?