I have have a chimney breast in the dining room that has been closed up
with plasterboard for years (before I moved in). When I repainted that
wall recently suddenly what looks like sweat patches have appeared
through the new paint up to 1 metre off the ground. I used an oil based
undercoat but this didn't help. I don't really want to open up the wall
so what is the best way to simply cover this up? Unless of course you
think I really ought to tackle the cause...


Raphael

lesshaste wrote:
I have have a chimney breast in the dining room that has been closed up
with plasterboard for years (before I moved in). When I repainted that
wall recently suddenly what looks like sweat patches have appeared
through the new paint up to 1 metre off the ground. I used an oil based
undercoat but this didn't help. I don't really want to open up the wall
so what is the best way to simply cover this up? Unless of course you
think I really ought to tackle the cause...


You are buggered mate.

Its one of two thimgs.

Rain coming down teh chimney - whuch could be capped if no longer used
and saoking into teh lower brickwork, or as in my case, a fireplace that
sits in an underfloor puddle under the house and is suffereing from
extreme rising damp.

Chimneys are desined to be ventilated, and have fires lit in them, which
normally pulls moisture introduced that way up the chimney.

The real answer is to cap the chimney, and put a DPC in the base.

You may care to investigate if water is getting under the house though,
assuming it has raised floors.

Sometimnes a french drain around the property prevents ingress.

The soil below a house SHOULD be bone dry..no water falls on it after
all, BUT if someone has built e.g/ solid paths around it that allow
water to run off THROUGH the underfloor vents INWARDS, or simply that
your local water table gets to be high after it rains, it isn't always so.



Raphael

I have had a problem with damp walls where the previous owner of the
house had removed the chimney breasts and stack completely. What they
didn't do was remove the foundations of the fireplace, but instead they
filled it in with random rubble and such like which had bridged the dpc
of the wall. May be somthing to bear in mind.

lesshaste wrote:
I have have a chimney breast in the dining room that has been closed up
with plasterboard for years (before I moved in). When I repainted that
wall recently suddenly what looks like sweat patches have appeared
through the new paint up to 1 metre off the ground. I used an oil based
undercoat but this didn't help. I don't really want to open up the wall
so what is the best way to simply cover this up? Unless of course you
think I really ought to tackle the cause...


Raphael

You may find the base of the chimney is full of soot, which seems to
hold moisture well for some reason.

lesshaste wrote:
I have have a chimney breast in the dining room that has been closed up
with plasterboard for years (before I moved in). When I repainted that
wall recently suddenly what looks like sweat patches have appeared
through the new paint up to 1 metre off the ground. I used an oil based
undercoat but this didn't help. I don't really want to open up the wall
so what is the best way to simply cover this up? Unless of course you
think I really ought to tackle the cause...


Raphael

It may be caused by rain coming in (eg roof leak, open chimneypot,
flashing or fillets), lack of ventilation or salt contamination. First
thing to check is youve got a vent grille in place, one should go in
when its sealed off.

Trying to stop it coming thru with waterproof paint will simply prevent
evaporation and thus is liable to make the patch gadually larger. Its
not going to solve the cause.


NT

"lesshaste" wrote in message
...
I have have a chimney breast in the dining room that has been closed up
with plasterboard for years (before I moved in). When I repainted that wall
recently suddenly what looks like sweat patches have appeared through the
new paint up to 1 metre off the ground. I used an oil based undercoat but
this didn't help. I don't really want to open up the wall so what is the
best way to simply cover this up? Unless of course you think I really
ought to tackle the cause...


Raphael

Not ruling out other causes like rain entry (and it's a good idea to put a
ventilating insert in the chimney pot anyway), but it does sound very much
like classic rising damp to me. The 1 metre high is the giveaway, plus it's
very common on older chimney breasts without DPC's, even when the walls are
unaffected sometimes.

I'm surprised nobody has asked if the chimney breast is on an internal or
external or a party wall. If it's an external wall there could be some
other defect that's relatively easy to cure, such as leaking
gutters/rainwater pipes, poor pointing or the ground level is too high. If
it's on an internal wall or on a party wall and next door is occupied, then
it's highly unlikely to be serious condensation in the flue as this only
forms on relatively much colder surfaces. In fact venting a flue from the
room can actually transport vapour up the flue and *encourage* condensation
in some circumstances.

Treating the wall surface with an impervious membrane (e.g. oil paint) will
most likely drive the moisture higher until it finds somewhere it can
evaporate. If you can live with the dampness then I would suggest you
remove the plaster up to 1m high and replaster with a lime-based plaster.
This will allow the moisture to evaporate more freely so it doesn't go as
high up the wall and will be much less obvious. That's how the house was
built in the first place. Whatever you do, you must get rid of any pink or
grey gypsum plaster as it will soak up the moisture like blotting paper and
then begin to crumble.

If you need to cure the dampness altogether, you'd be best installing a
damp-proof course at floor level, but you'll still have to renew the plaster
up to the 1 metre level.

Peter

In article ,
lesshaste writes:
I have have a chimney breast in the dining room that has been closed up
with plasterboard for years (before I moved in). When I repainted that
wall recently suddenly what looks like sweat patches have appeared
through the new paint up to 1 metre off the ground. I used an oil based
undercoat but this didn't help. I don't really want to open up the wall
so what is the best way to simply cover this up? Unless of course you
think I really ought to tackle the cause...

You can't cover it it -- it will just move somewhere else.
Is the chimney on an outside wall?
Is there a vent into the fireplace?
Is the top of the chimney open or closed and/or vented?

Chimneys must be vented top and bottom or they steadily get
more and more moisture trapped in them. I opened up a fireplace
which had been blocked off for 20 years at the top, and it was
wringing wet, with condensation running down the flue which
can't escape. It took 3+ months to dry out having put a vent
in the top and fully opened up the bottom. Capping the top
without venting it is much worse than leaving it open, but it
must be vented both top and bottom so there's a through-draft.
If the chimney is on an outside wall, the bottom vent can be
to the outside rather than into the room.

--
Andrew Gabriel

wrote:
lesshaste wrote:
I have have a chimney breast in the dining room that has been closed up
with plasterboard for years (before I moved in). When I repainted that
wall recently suddenly what looks like sweat patches have appeared
through the new paint up to 1 metre off the ground. I used an oil based
undercoat but this didn't help. I don't really want to open up the wall
so what is the best way to simply cover this up? Unless of course you
think I really ought to tackle the cause...


Raphael

It may be caused by rain coming in (eg roof leak, open chimneypot,
flashing or fillets), lack of ventilation or salt contamination.


First thing to check is youve got a vent grille in place,
one should go in
when its sealed off.

If the chimney is capped, you don't have a vent in the room. Think about it.



Trying to stop it coming thru with waterproof paint will simply prevent
evaporation and thus is liable to make the patch gadually larger. Its
not going to solve the cause.


NT

Stuart Noble wrote:
wrote:
lesshaste wrote:
I have have a chimney breast in the dining room that has been closed up
with plasterboard for years (before I moved in). When I repainted that
wall recently suddenly what looks like sweat patches have appeared
through the new paint up to 1 metre off the ground. I used an oil based
undercoat but this didn't help. I don't really want to open up the wall
so what is the best way to simply cover this up? Unless of course you
think I really ought to tackle the cause...


Raphael

It may be caused by rain coming in (eg roof leak, open chimneypot,
flashing or fillets), lack of ventilation or salt contamination.


First thing to check is youve got a vent grille in place,
one should go in
when its sealed off.

If the chimney is capped, you don't have a vent in the room. Think about it.


The cap should be vented.

MBQ

wrote:
Stuart Noble wrote:
wrote:
lesshaste wrote:
I have have a chimney breast in the dining room that has been closed up
with plasterboard for years (before I moved in). When I repainted that
wall recently suddenly what looks like sweat patches have appeared
through the new paint up to 1 metre off the ground. I used an oil based
undercoat but this didn't help. I don't really want to open up the wall
so what is the best way to simply cover this up? Unless of course you
think I really ought to tackle the cause...


Raphael
It may be caused by rain coming in (eg roof leak, open chimneypot,
flashing or fillets), lack of ventilation or salt contamination.

First thing to check is youve got a vent grille in place,
one should go in
when its sealed off.
If the chimney is capped, you don't have a vent in the room. Think about it.


The cap should be vented.

MBQ


How does that work then? What stops the rain blowing in?

In article ,
Stuart Noble writes:

How does that work then? What stops the rain blowing in?

Rain coming in through the open pot isn't a problem -- a
properly ventilated flue will dry that without any problem.
Blocking the airflow through a flue on an outside wall
is the problem. Moisture gets into the flue slowly through
the brickwork. Without ventilation, it can't get out at
the same rate, and you end up with condensation running
inside the flue. It usually concentrates at the bottom, but
you can get it coming though the wall anywhere. Flue must
be ventilated top and bottom to prevent this. Capping at
the top without ventilating will cause a damp flue.

Capping with a vent is the best option (particularly if a
tall stack is exposed to the weather), and second best is
just leaving the pot open. In either case, a vent at the
bottom is required too. If the chimney is on an outside wall,
the ventilation could be to the outside rather than to the
room.

--
Andrew Gabriel

Andrew Gabriel wrote:
In article ,
lesshaste writes:
I have have a chimney breast in the dining room that has been closed up
with plasterboard for years (before I moved in). When I repainted that
wall recently suddenly what looks like sweat patches have appeared
through the new paint up to 1 metre off the ground. I used an oil based
undercoat but this didn't help. I don't really want to open up the wall
so what is the best way to simply cover this up? Unless of course you
think I really ought to tackle the cause...

You can't cover it it -- it will just move somewhere else.
Is the chimney on an outside wall?
Is there a vent into the fireplace?
Is the top of the chimney open or closed and/or vented?

Chimneys must be vented top and bottom or they steadily get
more and more moisture trapped in them. I opened up a fireplace
which had been blocked off for 20 years at the top, and it was
wringing wet, with condensation running down the flue which
can't escape. It took 3+ months to dry out having put a vent
in the top and fully opened up the bottom. Capping the top
without venting it is much worse than leaving it open, but it
must be vented both top and bottom so there's a through-draft.
If the chimney is on an outside wall, the bottom vent can be
to the outside rather than into the room.


It is a Victorian terraced house and the chimney breast is on what I
think you call a party wall (a wall that two houses share in any case).
There is a small air vent in the plasterboard if I remember correctly
although it could of course be blocked. I really don't know what the
situation is with the top of the chimney as it would involve going on
the roof and there is no easy access without a very tall ladder.

The thing that is frustrating me is that before repainting there was no
obvious problem. This whole expensive looking problem seems to have just
appeared by repainting!

If I really have to have the thing opened up and treated by a
"professional" does anyone have a recommendation (e3, east london) for
someone who isn't a crook? I had a very bad experience last time I tried
to hire a damp proofing company.

Raphael

lesshaste wrote:

If I really have to have the thing opened up and treated by a
"professional" does anyone have a recommendation (e3, east london) for
someone who isn't a crook? I had a very bad experience last time I tried
to hire a damp proofing company.

Raphael

one of the reasons we diy


NT

lesshaste wrote:
Andrew Gabriel wrote:
In article ,
lesshaste writes:
I have have a chimney breast in the dining room that has been closed
up with plasterboard for years (before I moved in). When I repainted
that wall recently suddenly what looks like sweat patches have
appeared through the new paint up to 1 metre off the ground. I used
an oil based undercoat but this didn't help. I don't really want to
open up the wall so what is the best way to simply cover this up?
Unless of course you think I really ought to tackle the cause...

You can't cover it it -- it will just move somewhere else.
Is the chimney on an outside wall?
Is there a vent into the fireplace?
Is the top of the chimney open or closed and/or vented?

Chimneys must be vented top and bottom or they steadily get
more and more moisture trapped in them. I opened up a fireplace
which had been blocked off for 20 years at the top, and it was
wringing wet, with condensation running down the flue which
can't escape. It took 3+ months to dry out having put a vent
in the top and fully opened up the bottom. Capping the top
without venting it is much worse than leaving it open, but it
must be vented both top and bottom so there's a through-draft.
If the chimney is on an outside wall, the bottom vent can be
to the outside rather than into the room.


It is a Victorian terraced house and the chimney breast is on what I
think you call a party wall (a wall that two houses share in any case).
There is a small air vent in the plasterboard if I remember correctly
although it could of course be blocked. I really don't know what the
situation is with the top of the chimney as it would involve going on
the roof and there is no easy access without a very tall ladder.

The thing that is frustrating me is that before repainting there was no
obvious problem. This whole expensive looking problem seems to have just
appeared by repainting!

If I really have to have the thing opened up and treated by a
"professional" does anyone have a recommendation (e3, east london) for
someone who isn't a crook? I had a very bad experience last time I tried
to hire a damp proofing company.

Raphael

You only need a local odd job man really.

Stuart Noble wrote:
wrote:
Stuart Noble wrote:
wrote:
lesshaste wrote:
I have have a chimney breast in the dining room that has been closed up
with plasterboard for years (before I moved in). When I repainted that
wall recently suddenly what looks like sweat patches have appeared
through the new paint up to 1 metre off the ground. I used an oil based
undercoat but this didn't help. I don't really want to open up the wall
so what is the best way to simply cover this up? Unless of course you
think I really ought to tackle the cause...


Raphael
It may be caused by rain coming in (eg roof leak, open chimneypot,
flashing or fillets), lack of ventilation or salt contamination.

First thing to check is youve got a vent grille in place,
one should go in
when its sealed off.
If the chimney is capped, you don't have a vent in the room. Think about it.


The cap should be vented.

MBQ


How does that work then? What stops the rain blowing in?

A properly designed vented chimney cap will let very little rain in.
What does get in will simply dry when it isn't raining.

MBQ

DIY the damp proofing then you know its done and done properly.

I havn't tried it yet but have just ordered this:

http://cgi.ebay.co.uk/ws/eBayISAPI.d...MEWN%3AIT&rd=1

As soon as it arrives I'll be damp proofing around our old fireplace.
I don't think it needs it as per my last post but im doing it anyway as
we are paying for the whole room to be re-plastered and what to make
sure the damp problem is solved.

There are some alternatives, dryzone is another varient of the cream as
above but is more expensive. The other method involves pressure pumps
which still is within DIY but a little more work.


Chris.

hyte1 wrote:
DIY the damp proofing then you know its done and done properly.

I havn't tried it yet but have just ordered this:

http://cgi.ebay.co.uk/ws/eBayISAPI.d...MEWN%3AIT&rd=1

As soon as it arrives I'll be damp proofing around our old fireplace.
I don't think it needs it as per my last post but im doing it anyway as
we are paying for the whole room to be re-plastered and what to make
sure the damp problem is solved.

There are some alternatives, dryzone is another varient of the cream as
above but is more expensive. The other method involves pressure pumps
which still is within DIY but a little more work.


Chris.


I hope your confidence isn't misplaced. Might be easier to sort the
source out.

Problem has been sorted - previous owner removed fireplace and chimney
breast but left in foundations of fireplace under floorboards. The gap
was filled with random rubble and sand etc which I have now removed.
I'm putting in the damp proof cream as an extra measure although I
suspect I don't really need to.

I thought that seen as the floor is lifted, its worth £5 a tube of
damp proof cream.

Cheers.

lesshaste wrote:
If I really have to have the thing opened up and treated by a
"professional" does anyone have a recommendation (e3, east london) for
someone who isn't a crook? I had a very bad experience last time I tried
to hire a damp proofing company.

Before calling someone in I'd try a couple of basic things:

Firstly are you sure that the vent isn't blocked? Is there any way
that you can take it off & have a look?

Secondly if it was all OK until you painted it with an oil based paint
that suggests that in the past it was getting enough ventilation to
stay dry - is there any way that you can remove it and see if that
returns it to it's previous state? (Obviously if the plaster's shot
you may have to replace it anyway).

Michael