Strange concrete floor problem...
Pecanfan
I've started on our latest renovation escapades and have found a strange
problem with the kitchen floor. It's a 1930's brick-built semi and the
kitchen floor (downstairs at the back of the house) is concrete. The rest
of the downstairs floors are suspended timber by the looks of it (there's
laminate down at the minute).
Anyway, just ripped the shockingly-laid laminate up in the kitchen and found
that part of the floor is solid concrete but the rest feels suspended -
there's significant give in some areas and it feels more like a timber floor
when you're walking on it. It's definitely concrete though!
So I knocked a big hole in it to see what's going on (there's serious damp
on the back wall and was worried any joists suspending a concrete floor
might have rotted, hence the give) but the floor would appear to be
suspended... on nothing! There's no void under it so it wouldn't appear to
the suspended - and I couldn't find any joists. The concrete is about 4-5"
thick and I managed to get my arm underneath to feel at least a 1" gap
between the concrete and the earth beneath (in that area anyway - the area
with the most give).
As I say, parts of it feel perfectly solid, a couple of bits have
significant give (5-10mm) and some are solid enough but feel like a normal
timber floor when you jump on it.
Anyone come across anything like this before? Seems very odd. Read
something about Sulphur attacks but couldn't find much more about it.
Should I worry? I need to level the floor anyway - I gather latex is the
way forwards with a 'bouncy' concrete floor?
TIA!
Andy
meow...@care2.com
Never come across that before. If you ram some stone down there when
you fill the hole you're giving it an extra solid support, and halved
span means much less give. If its bad enough you could put a few new
supports in this way.
NT
Roger
from "Pecanfan" <peca...@no.spam> contains these words:
> Anyone come across anything like this before? Seems very odd. Read
> something about Sulphur attacks but couldn't find much more about it.
> Should I worry? I need to level the floor anyway - I gather latex is the
> way forwards with a 'bouncy' concrete floor?
Not seen anything like that.
I take it you don't have any damp protection under the floor not any
reinforcement in the concrete.
The void could be as a result of a serious water leak a long time ago or
perhaps it was a jerry built replacement floor without a proper sub base
and whatever fill was used has since shrunk.
Personally I would be tempted to dig it out and put in a proper
insulated concrete floor. Concrete isn't good in tension so as it is
there is always the possibility that it will fail some time in the
future. Digging out will also give you a chance to do something
constructive about the damp wall.
--
Roger Chapman
Pecanfan
> reinforcement in the concrete.
I've taken up) and it's not reinforced. The floor itself is perfectly dry
though.
> Personally I would be tempted to dig it out and put in a proper
> insulated concrete floor. Concrete isn't good in tension so as it is
> there is always the possibility that it will fail some time in the
> future. Digging out will also give you a chance to do something
> constructive about the damp wall.
Tempted with that option - looking at the price of self-leveller it may
actually be the cheaper option anyway! And as you say it would give room to
get the damp proof injection below floor level.
Cheers,
Andy
Phil L
Anything other than what Roger said is wasting money - rip it all out, dig
out 150mm and put in 150mm of polystyrene, then DPC membrane, then 100mm of
fresh concrete...the ground has sunk away, this is what happens when the
ground isn't properly prepared prior to laying concrete, or the infill isn't
properly compacted, you may also want to bung some steel mesh in there, for
£15, it's not worth leaving out.
auct...@sheldononline.co.uk
Had something very similar in our first house. The kitchen floor had an
old water pipe underneath which had been folded over to seal it off,
but was still connected. I think it was the supply for the outside loo
before the room was knocked through to be the kitchen. The slow leakage
over the years had caused the ground to drop by about 2 inches leaving
a cavity.
We removed the concrete and fitted a new floor. The upside was that it
made getting the concrete out easy - one bash with a sledgehammer and
the whole thing dropped!
A
Brian Sharrock
<auct...@sheldononline.co.uk> wrote in message
news:1168162221.4...@s80g2000cwa.googlegroups.com...
>
> Pecanfan wrote:
>> Hi all,
>>
>> I've started on our latest renovation escapades and have found a strange
>> problem with the kitchen floor. It's a 1930's brick-built semi and the
>> kitchen floor (downstairs at the back of the house) is concrete. The
>> rest
>> of the downstairs floors are suspended timber by the looks of it (there's
>> laminate down at the minute).
>>
>> Anyway, just ripped the shockingly-laid laminate up in the kitchen and
>> found
>> that part of the floor is solid concrete but the rest feels suspended -
>> there's significant give in some areas and it feels more like a timber
>> floor
>> when you're walking on it. It's definitely concrete though!
>>
This may not directly address your point .... in my 1935 built house the
kitchen floor was constructed in different ways . At the two end corners
there were plinths of concrete laid over with quarry tiles - the plinth in
one corner supported a Rayburn cooker/heater while the plinth in the other
corner supported a thirties-vintage gas cooker. Separated from these plinths
was another longer one under the window. This longer plinth supported a
'Butler's Sink' - on brick piers ! The other areas of the floor were
suspended timber - as is the rest of the house. AIUI flooring need not
necessarily be all of one type.
--
Brian
The Natural Philosopher
sledge and a barrow will net you some nice hardcore that you can use
later to ill the voids. Up it all comes, damp inject whats needful with
full access - heck even underpin if you want, and lay a new slab over
sand filled hardcore, and stick some mesh in it too, Then a nice slab of
polystyrene and a screed with UFH. Magic!.
Or if its a big space and the subsoil is unstable, lay some strip
fundations along the insides and put a block and beam concrete floor in.
Weatherlawyer
I am almost certain that your house predated widespread use of
concrete. In fact cement wasn't even widely used. Perhaps the original
floors now concrete, were clay tiles at one time. These were laid on
earth and would have fallen with it, if there was any subsidence.
Then the occupier tiring of any unevenness laid concrete instead.
Or perhaps it was a genuine good job not just a bodge up but the ground
fell away without taking the floor with it. As well as happening as the
others have suggested settlement of the hardcore, water erosion and
that, it might be a geological fault where a layer of clay over a sand
(or something like sand for shrinking when drained) has collapsed as
the aquifer -or water table, fell.
It's not that uncommon in the UK. I'm not sure that is a slowquake but
you get the idea. Before going to any expense I would be prepared to
shell out a few hundred finding the cause of the fault.
If it was due to land drainage, it could come back up one day. Of
course in this weather it should be doing that now.
Pecanfan
> concrete. In fact cement wasn't even widely used.
I'm fairly sure concrete has been around longer than the 1930's. My last
place was early 1900's and had original concrete floors. Wasn't the
Pantheon made of concrete? ;-)
Andy
Pecanfan
> sledge and a barrow will net you some nice hardcore that you can use later
> to ill the voids. Up it all comes, damp inject whats needful with full
> access - heck even underpin if you want, and lay a new slab over sand
> filled hardcore, and stick some mesh in it too, Then a nice slab of
> polystyrene and a screed with UFH. Magic!.
Cheers everyone for the advice - up it comes! :-) To be honest, now that
I'm looking under the floor I'm wondering if it's actually the concrete
floor that's causing the damp problems in the wall - the 'soil' base to the
concrete certainly bridges the DPC and it would also explain why this is the
only room with rising damp.
It's a relatively small area (1.1m3) so happy to tackle it myself - anyone
come across any good step by step guides for concrete laying? Presumably
there's no need for formers since the walls will do that, with the DPM
extending up between the wall and the concrete of course. So how do you get
the concrete to the desired height - just marker pegs or something? But
that would penetrate the DPM... ?
Out of a matter of interest, does the polystyrene not introduce an element
of 'bounce' to the floor?
Andy
Weatherlawyer
Yes, according to the price the customer was willing to pay, the needs
of the structure would incorporate whatever was known in the time of
its knowledge. We know Wren used Portland Cement. But then he was
rebuilding London and water freight and the mass market might have
stood for it. Or there again perhaps he just used it on St Paul's.
But it is unlikely an expensive import would be carted by train and by
horse to your house in the 1930's when a clay tile floor would have
sufficed for the servants.
Do you really think it would?
There was hardly the draw on qualified builders that a national
disaster would create and most dwellings even now just used the best
that is available according to the work skills in the area.
And not even always then. A surprising amount of rubbish goes into a
building. Consider fly ash and asbestos. One was a locally produced
crap material the other a cheap import ...but an import no less.
Today its tin studding held together by plasterboard and black screws
or aerated blockwork.
The Natural Philosopher
Prior to that other lime based concrete type materials existed, but
lacked the strength. You can see such in old castle ruins and so on..the
walls were filled with cement and flint. Well mortar and flint anyway.