Concrete floor and dampness


B

BartC

I've found some dampness under the vinyl flooring in the hallway of my late
60s concrete-floored house.

The concrete is still mostly covered with brittle brown tiles, and the
concrete where exposed (missing bits of tiles) has some black stuff painted
on it (or maybe it was the glue for the tiles).

The vinyl was put down temporarily a few months back (one day I'll put
laminate down), but recently discovered a damp area underneath, together
with white powdery stuff on the concrete, causing the floor to swell
slightly.

What's the best way to deal with this? Someone I called out last year wanted
to coat the entire ground floor for £400 (but I wasn't sure then if it was
rising damp or a leak from somewhere). Would this work, or would any sort of
coating just drive the moisture towards the walls?

Thanks.
 
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T

Tim Watts

BartC said:
I've found some dampness under the vinyl flooring in the hallway of my
late 60s concrete-floored house.

The concrete is still mostly covered with brittle brown tiles, and the
Watch those - some possibility they might contain asbestos, so reasonable
precautions when removing should be considered.

concrete where exposed (missing bits of tiles) has some black stuff
painted on it (or maybe it was the glue for the tiles).
Bitumen compound most likely - probably tile glue and would have acted as a
DPM (damp proof).
The vinyl was put down temporarily a few months back (one day I'll put
laminate down), but recently discovered a damp area underneath,
I had similar in a 50's built house with the sam efloor structure.
together
with white powdery stuff on the concrete, causing the floor to swell
slightly.
Concrete salts?
What's the best way to deal with this? Someone I called out last year
wanted to coat the entire ground floor for £400 (but I wasn't sure then if
it was rising damp or a leak from somewhere). Would this work, or would
any sort of coating just drive the moisture towards the walls?
Good question. You could do it yourself (I did) - with an epoxy DPM. The
stuff is not cheap, so it's going to cost a fair fraction of that just for
the epoxy. But it is very easy to apply - roller on 2 coats at 90 degrees to
each other (to avoid pinholes). Look for "F Ball" on google - they make the
one I used and have all appplication details on their website.

What will be not so easy in your case is removing the bitumen. You cannot
have *any* remaining before an epoxy DPM. Basically, it's floor grinder time
if you go down that route and take the bitument and a couple of mm of screed
off. Rather messy operation (I did it).


I bet your tradesman did not include that in his quote.


There are other options - which depend on what floor covering you want. The
most obvious is to have another flooring that you can use *more* bitumen
compound to stick down. Another is a floating floor (eg engineered wood,
laminate - where you can loose lay a heavy plastic DPM under the whole lot.


Re walls: the floor was DPM'd via the bitumen before - if you were going to
get any damp in the walls, I think it would have happened by now.

Cheers

Tim
 
N

NT

Watch those - some possibility they might contain asbestos, so reasonable
precautions when removing should be considered.
yes, the asbestos will be bound in the vinyl though, making the risk
as good as zero.

Bitumen compound most likely - probably tile glue and would have acted asa
DPM (damp proof).




I had similar in a 50's built house with the sam efloor structure.


Concrete salts?
that seems to imply that water ingress into the slab is ongoing


It would cost you £10-20 to it with bitumen gloop. It is slow setting,
don't paint yourself into a corner :)


It would. Whether it would be a problem is another matter, each
element of the building can evaporate a certain amount of water
without harm.
Good question. You could do it yourself (I did) - with an epoxy DPM. The
stuff is not cheap, so it's going to cost a fair fraction of that just for
the epoxy. But it is very easy to apply - roller on 2 coats at 90 degreesto
each other (to avoid pinholes). Look for "F Ball" on google - they make the
one I used and have all appplication details on their website.

What will be not so easy in your case is removing the bitumen. You cannot
have *any* remaining before an epoxy DPM. Basically, it's floor grinder time
if you go down that route and take the bitument and a couple of mm of screed
off. Rather messy operation (I did it).

I bet your tradesman did not include that in his quote.
Thats what I call making life difficult.
There are other options - which depend on what floor covering you want. The
most obvious is to have another flooring that you can use *more* bitumen
compound to stick down. Another is a floating floor (eg engineered wood,
laminate - where you can loose lay a heavy plastic DPM under the whole lot.

Re walls: the floor was DPM'd via the bitumen before - if you were going to
get any damp in the walls, I think it would have happened by now.

Cheers

Tim
Another approach is to use a floor surface that lets the damp
evaporate off. Then it just dries out.


NT
 
J

Jim K

yes, the asbestos will be bound in the vinyl though, making the risk
as good as zero.







that seems to imply that water ingress into the slab is ongoing


It would cost you £10-20 to it with bitumen gloop. It is slow setting,
don't paint yourself into a corner :)


It would. Whether it would be a problem is another matter, each
element of the building can evaporate a certain amount of water
without harm.




Thats what I call making life difficult.





Another approach is to use a floor surface that lets the damp
evaporate off. Then it just dries out.

NT
mmmm dries out continually into the living space.....

Jim K
 
N

NT

mmmm dries out continually into the living space.....

Jim K
Lots of houses do that. There's no harm in water vapour, all houses
have plenty of it, problems only occur when it gets excessive.


NT
 
T

Tim Watts

NT said:
yes, the asbestos will be bound in the vinyl though, making the risk
as good as zero.
Indeed. That's why I said "reasonable" - taking them up with a spade or a
bolster would be OK. Grinding them off would be bad.
that seems to imply that water ingress into the slab is ongoing
My assumption with a floor of that age is that it is highly likely...
It would cost you £10-20 to it with bitumen gloop. It is slow setting,
don't paint yourself into a corner :)



It would. Whether it would be a problem is another matter, each
element of the building can evaporate a certain amount of water
without harm.


Thats what I call making life difficult.
That depends on what sort of floor you want on top. I wanted slate - so no
way was I going to leave a bitumen layer there.

For 400 quid, the OP's tradesman was either going to paint more bitumen on
and rob the OP, or paint on epoxy without doing the necessary preparation
and in a while it would fail, thus robbing the OP again.
Another approach is to use a floor surface that lets the damp
evaporate off. Then it just dries out.
This is another reasonable approach.
 
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T

Tim Watts

Jim K wrote:

mmmm dries out continually into the living space.....
If it's only "a bit" it would be fine. If the whole floor had an earthy
smell like my kitchen did (once the top layer of bitumen was off) - that
would be too much.

Some old cottages had brick floors where the bricks were laid on earth.
 
D

Dave Liquorice

Lots of houses do that. There's no harm in water vapour, all houses
have plenty of it, problems only occur when it gets excessive.
Like trapped under a DPM... How much water/hour does the human body
chuck out simply by breathing?
 
S

stuart noble

Indeed. That's why I said "reasonable" - taking them up with a spade or a
bolster would be OK. Grinding them off would be bad.


My assumption with a floor of that age is that it is highly likely...


That depends on what sort of floor you want on top. I wanted slate - so no
way was I going to leave a bitumen layer there.

For 400 quid, the OP's tradesman was either going to paint more bitumen on
and rob the OP, or paint on epoxy without doing the necessary preparation
and in a while it would fail, thus robbing the OP again.


This is another reasonable approach.
Pros won't lay floor coverings on a solid floor without latex screed.
This invariably adds a day to the job but presumably solves the problem
 
T

Tim Watts

stuart said:
Pros won't lay floor coverings on a solid floor without latex screed.
This invariably adds a day to the job but presumably solves the problem
SLC (levelling compounds) will never bond correctly to bitumen - which is
why I had to grind mine off. No real pro would do that, though there are
plenty of cowboys who will.

There is a school of thought that more bitumen blinded with sand immediately
is acceptable, but it's the sort of thing I'd want professional advice on -
or at least well considered advice.

I have seen what happens to SLC on bitumen - it seems OK, then after a few
heating/cooling cycles it shears the bond over large areas. My plasterer has
also been a victim of this in a previous life when he worked in Germany on
converting some old bunkers into habitation.

They had to take the SLC off again (bond shear set in so it was easy). A
regime was worked out professionally for that one that involved drilling
lots of small (1cm I guess) dia holes an inch or so into the screed at very
regular and close intervals then pouring suitable rated SLC. The idea was
the SLC would pour into the holes and peg itself in place, bypassing teh
bitumen layer.

Apparantly that worked. You'd want to choose the SLC carefully too - not any
old crap from B&Q. Also for pegging, the SLC thickness would matter as you
are relying on its self strength to hold up between the "pegs" so a 3mm pour
would probably not work. I suspect a 10mm pour of good stuff with holes
every 6" may work quite well - and although that's a lot of holes, they are
shallow and an SDS would make short work of it.

I would not want to guarantee that approach through unless the SLC
manufacturer was consulted - or a professional flooring contractor.
 
S

stuart noble

painting solvent bitumen on will dissolve the existing bitumen, so that
approach is quite workable. The one downside is bitumen with solvent
is very slow drying, so you'd want to not do it all at once if the
house is occupied.

The original solvent doesn't normally dissolve the hardened film e.g.
white spirit has no effect on oil based paints
 
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R

Roger Mills

I've found some dampness under the vinyl flooring in the hallway of my
late 60s concrete-floored house.

The concrete is still mostly covered with brittle brown tiles, and the
concrete where exposed (missing bits of tiles) has some black stuff
painted on it (or maybe it was the glue for the tiles).

The vinyl was put down temporarily a few months back (one day I'll put
laminate down), but recently discovered a damp area underneath, together
with white powdery stuff on the concrete, causing the floor to swell
slightly.

What's the best way to deal with this? Someone I called out last year
wanted to coat the entire ground floor for £400 (but I wasn't sure then
if it was rising damp or a leak from somewhere). Would this work, or
would any sort of coating just drive the moisture towards the walls?

Thanks.
How big - and what shape - is the damp area? Could there be a leaking
pipe buried in the floor?

It's best to deal with the cause rather than the symptoms, if you can.
--
Cheers,
Roger
____________
Please reply to Newsgroup. Whilst email address is valid, it is seldom
checked.
 
M

Martin Brown

The original solvent doesn't normally dissolve the hardened film e.g.
white spirit has no effect on oil based paints
That is because most oil based paints polymerise as they dry so the
resulting paint film is crosslinked. It may still soften with a solvent
but it won't normally dissolve once it has fully cured to dryness.

Bitumen will dissolve in solvent although the solvent is smelly stuff
and bad to breath (extremely high VOCs) and bitumen gets everywhere!
 
S

stuart noble

That is because most oil based paints polymerise as they dry so the
resulting paint film is crosslinked. It may still soften with a solvent
but it won't normally dissolve once it has fully cured to dryness.

Bitumen will dissolve in solvent although the solvent is smelly stuff
and bad to breath (extremely high VOCs) and bitumen gets everywhere!
IIRC cellulose thinners softens bitumen but isn't a practical
proposition because it evaporates too quickly and stinks to high heaven.
 
S

stuart noble

Bitumen is after all merely a long chain hydrocarbon and should dissolve
in any shorter one - petrol diesel, turpentine or white spirit..there is
no need to get fancy and use the ketones!
Interesting. Not a job I hope to encounter again, but I'll bear that in
mind.
 
M

Martin Brown

Interesting. Not a job I hope to encounter again, but I'll bear that in
mind.
Also bear in mind the flash point and fairly wide range of explosive
concentrations if using the more volatile ones.
 
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N

NT

Also bear in mind the flash point and fairly wide range of explosive
concentrations if using the more volatile ones.
Bitumen has dissolved whenever I've put the right solvents on.
Paraffin is almost no-whiff and no exposion risk, but very slow
drying. White spirit's quick, volatile and a bit too flammable for my
liking.


NT
 
B

BartC

How big - and what shape - is the damp area? Could there be a leaking pipe
buried in the floor?

It's best to deal with the cause rather than the symptoms, if you can.
The worst damp spot had been at the bottom of a door-frame, which seemed to
extend well into the concrete, if not beyond. The wood was soft, wet and
rotten. But the nearest buried CH pipe runs past the frame on the other
side, and that wood was sound. The only other possible pipe might be the
incoming mains, but if there is a leak then it's not showing up on the water
meter in the road; if the stop-cock is turned off under the sink, any
residual flow stops, and usually no flow is shown most of the time.

The current area is perhaps 3x5" in the middle of the hallway, where there
was a similar-size area of the brown tiles missing, but the dampness had
permeated radially from there on the underside of the vinyl. The same floor
had been used with no vinyl, just the tiles, for a month or so with no
obvious damp.

There were a few other spots of damp, one in the middle of a laminated
floor, causing it to swell and then split. But this was pretty much where a
wall (between dining room/lounge) had once been, and was unlikely to be near
a CH pipe. So it's possible any damp-proofing had been damaged.
 
T

The Natural Philosopher

Martin said:
Also bear in mind the flash point and fairly wide range of explosive
concentrations if using the more volatile ones.
indeed. Always use the heaviest solvent that works - white spirit and
diesel are the safest and least likely to poison you.
 
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T

The Natural Philosopher

NT said:
Bitumen has dissolved whenever I've put the right solvents on.
Paraffin is almost no-whiff and no exposion risk, but very slow
drying. White spirit's quick, volatile and a bit too flammable for my
liking.


NT
+1
 

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