"rrh" wrote in message
...
10-12 years ago I packed out the gaps which had developed between the
sleeper walls on top of the concrete float and the joists supporting our
timber kitchen floor (1920s semi, North London). The floor had become
bouncy
again and with new kitchen units en route and some electrics needing
attention, it was time today to rip it up again. I found some small gaps
from extra settlement over the intervening years, but no more than you'd
expect. But the real problem appears to be around the boiler alcove in the
middle of one wall - presumably once a fireplace. This is an area I didn't
even look at when packing the joists before. There seems to be a brick
sleeper-type wall built out around the former fireplace area. The middle
of
it seems to be full of old builders' rubble into which I can poke a stick
for a long way but there is a concrete shelf above - thankfully sound as
far
as I can see - supporting the boiler. As you can see from this pic:

http://www.justigator.pwp.blueyonder.../DSC00681a.jpg

three of the joists are supposed to rest on the wall top but the wall has
settled and a gap has opened up (there was also originally a length of
joist
timber along the concrete edge at right angles to the joists which was
completely rotten and providing no support). To judge from the amount of
curve in the floorboards, the joists have dropped some 20mm and are now
not
properly supported at their ends - although they are at the sleeper wall
in
front (packing shown is undisturbed from last time). It may not be clear
from the photo but the top of the problem wall has a pronounced lean
towards
the camera - enough to make me unwilling to just put more packing under
and
seal up again, for fear of it just collapsing under the extra weight.


I'm a bit confussed, but can't you just pack the 20mm with broken slate
tiles? I raise part of our floor that way. Jack up the joist with a car
jack, put in the slate shimm and relax the jack.

Scott