As others have said, try to identify the source of the damp before laying
final floor coverings.
Do you have any hot water pipes or heating pipes in this area?
If you have the usual hot water circuit for the time (with hot water from an
indirect cylinder heated by your boiler), then a small leak may not show
immediately as water flowing through your meter. The vagueness of float
valves in storage tanks means that small quantities of water can be drawn
without make up water being immediately needed to replace it.
I have a 1973 property of similar construction to yours. When we moved in
about 10 years ago it was discovered that a damp patch was not due to a
dodgy patio door, but down to a fractured elbow on a hot water pipe that had
clearly been leaking for some time. This had caused rotting of some
skirtings and door frames. The damp was just at a level where an inspection
didn't show anything too alarming, but once in, the effects were found to be
quite wide spread. Water had tracked under most of the original tiled floor
covering, so this has all been removed.
One issue with pipes laid in solid floors is that a leak can develop, but
the resulting damp may creap along the pipe channels and affect other areas.
If you don't have a good handle on pipe routes, I would try to establish
these as it may help pinpoint the source of the problem.
If you have a combination of damp and swelling floor in a 1960's house
there is a possibility that the floor was constructed using blast
furnace slag or other industrial waste. This was common from 1945 to
1970 especially in areas near steelworks or collieries. The sulphate
bearing hardcore reacts with the concrete and causes irreversible
metaliferous slags caused similar problems
It would be worth asking if this is a known problem in housing in your
area as if that is the case resurfacing the floor will be ineffective.
The actual swelling is slight, and might be just salts pushing up the tiles.
I'm not getting of those major symptoms described, although the house *is*
in a colliery area.
But, the floor sounded hollow around there (more like a wooden floor!). I
dug up few inches, and underneath a harder top later of a few mm, the
concrete was dry and powdery (I could dig it out with my fingers).
So, now what? I admit I don't even have any idea what kind of tradesman to
call for an opinion (and suspect they will recommend works whether they are
needed or not).
However the main problem was the dampness (the floor was still doing it's
job of being walked on!) (And if it was subject to sulphur attack, the
document suggests nothing need be done in early stages. I think it also says
somewhere that allowing evaporation of moisture will make things worse by
speeding up the reaction.)
I'm trying to understand in more detail how the concrete flooring works in
this house built around 1967.
Presumably, the walls are built first, including interior walls, with their
own DPC in the brickwork.
Then, concrete floors are added, up to each wall, in the form of a proper
concrete layer, then a thinner, smoother layer called a 'screed'?
Where would the damp-proof membrane have been in this construction; would it
have just have been the black bitumen coating on top of the screed layer?
(This corresponds to the level of the DPC in the walls.)
What I don't understand is how the wooden structures (stairs, understair
housing and door frames) fit on top of the concrete: they seem to go below
floor level (and below that bitumen layer), yet do not suffer from dampness
(apart from one side of one door frame; the other two original doors were
removed as the downstairs became open-plan so don't know what they were
(And is it likely the CH pipes - in an unusual single-pipe circuit layout -
would have been fitted at the time of the construction? As many go below the
concrete, but I can't see any signs of major disruption where they run
(although I can only see where one pipe runs, in the hallway; elsewhere
there is stone tile or laminate and I haven't looked.)
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