In article , Franz Heymann
writes

"John Rouse" wrote in message
...

I've been digging out a lot of the "pot clay" (yellow in our case) which
someone kindly dumped under our drawing room floor (don't ask!).

My curiosity insists that I must ask.

You may regret it. Our house is called "Springfield House" which should
have given any half-brained surveyor the clue that there were
underground watercourses in the area. It is built between two lines of
bassetting, and there is a lot of free water under the building. For
this reason the neighbours tree roots thought it would be an ideal place
to hang out, resulting in the building subsiding.

At some stage in the past, someone's answer to this problem (rather than
to clear out the stone drains around the cellar that were installed when
the house was built, and which drain into the main sewers) decided that
a better idea would be to fill the underfloor voids in the non-cellar
areas with rubble (including wood shavings, bricks and plaster) and then
cap the whole lot off with clay. Just for good measure they dumped pure
clay in places. In theory the plaster and wood shavings should have
broken down the clay into something quite nice, but without air or
organisms it doesn't quite happen like that.

Consequently I have been digging out some of the clay at the edges
(being careful not to get too near the footings - don't want them drying
out!) in order to try and improve the ventilation and reduce the damp.
--
John Rouse