My house was built in 1968 and we have lived there since new. It has
traditional 10inch cavity walls and concrete floor (on the ground floor). At
the rear of the property the floor slab has dropped by about 5mm. This is
not a recent thing, but happened very early in the buildings life and has
been stable for many years.
My problem is that the floor over a door opening (over the inner course of
brickwork) has not dropped and the resulting step makes carpet laying
difficult and the thin concrete layer was starting to break up.
I have chipped away the concrete floor at the opening to reveal the inner
course of bricks and the cavity. The top of this inner course appears to be
coated with a hard grey resin-like material, which I think formed a dampness
barrier (this is at the same level as the damp course and looks to have be
put on with a trowel). This had adhered well to the brick and concrete but
mostly came of when I chipped away the broken concrete. The cavity itself
was filled with sand and rubble (now removed) to support the thin concrete
above and appeared to be smeared with the same resin-like material as above,
but this was very thin and week. Both the inner and outer courses of brick
and the sand in the cavity are slightly damp to the touch.
My question is -
Should the sand and rubble in the cavity be removed? If so, what should be
placed into the cavity to support the new concrete that will eventually
What can I use to replace the "resin-like" material; it must act as a
moisture proof barrier over the inner course of brick and whatever I use to
bridge the cavity, plus it must adhere to brick and allow concrete to adhere
I anyone can offer any advise I would be most grateful.
Regards to all