The concrete is likely to be 100-150mm thick but there may be a screed on top of this so another 50-75mm.  Under the screed you will probably find some hardcore, to determine the total depth lift a floorboard in an adjacent room to see what the space is under the floor as it is likely to be the same in all rooms. Provided you don't excavate below this level there should be no risk to the foundations which will probably not be that deep.

Depending on the span wall to wall you will need to replace any honeycomb sleeper walls to support the ends of the joists as well as at regular intervals. Place a DPC onto these sleper walls, don't build the joists into the walls, use tanalized timber and either traditional floorboards or chipboard/plywood flooring.

Jason

Thanks Gents,

I was worried that it might be a deep layer of concrete that would take ages / cost loads to remove.  That depth doesnt sound too bad.  I am planning a 'proper' floorboard floor, apparently I can pop over to France and buy very nice chestnut floorboards as cheap as the chipboard stuff.

One question Jerry, why do I need to put a layer of concrete down?  Or do you mean under the joist supports ?

Thanks

Mark

Quote:


Do let me know if you find any good bargins.

Colin (in Belgium right now but building in the UK)

Hi,  back with a further question.

Ive started breaking the floor up in one corner (so I can hide it behind the sofa when the mrs gets in)  It seems like its just a skim.  the depth of concrete varies (over about 2sq m)  from 2" down to about 1" some has hard core under and some doesnt.  Its all sitting on a polythene membrane which seems to have soil under it.
The wall at a depth of 2 inches changes from being good brick to stone/brick and is rough rather than smooth finished.  This isnt a load bearing wall, btw, it only has floorboards above it and the beams go through it and over the adjacent passageway before terminating in a solid wall.

I have not yet taken the wooden floor up in the next room.

Would it be likely that this fllor would have originally been stone / tile laid on soil?  I cannot see that I will be digging out enough to put a wooden floor down after all.

thanks

Mark

Colin,

I can beat that fairly easily.

have a look on http://www.salvoweb.com  then go into the for sale section.  You have to wade through a lot of stuff but there is good quality oak flooring from £15/m².  
Obviously depends what you want, new or reclaimed, oak/elm/pine/etc, boards, strip, parquet, etc.  but there is both reclaimed and new on here.