I have a Victorian townhouse, it appears to have been built without a
DPC at all, there isn't even a slate one I can find.

The problem I have is that the previous owners have had a chemical
damp proof course installed over much of the house and it hasn't
entirely worked. Some areas that have no DPC have no damp problem at
all... Most of the house is fine, but there are two areas (both
internal), one of plain wall and one around a hearth where there is
damp and chemical DPC.

I suspect the problem is very minor but is being made a lot worse by
the fact that a membrane has been fitted between the brick and the
plaster up to a height of 1m. This means that there is a line of damp
at 1m accross my wall.

Now, I am not sure if all the damp around the hearth is rising damp, I
suspect it might simply be rain coming down the chimney (not capped,
it fell off a year or so ago).

For the rest which is rising damp, I can see two, maybe three courses
of action.
1) Put in an extra layer of chemical DPC.
2) As I suspect the damp isn't serious, remove the membrane backed
plaster and simply paster over it with regular plaster, hoping that
the damp will simply evaporate.
3) Go along brick by brick, and somehow install a membrane DPC.

I'm replacing the fireplace around one area, so am tempted by option 2
there. For the wall it has to be 1 or 3.

Is option 3 viable? Is it ever done? I know it would be very time
consuming but I have a lot of time!

Now, next issue is the hearth itself, I'm fairly sure this is rising
damp and not from the chimney. Oddly enough, only the room side wall
of the hearth seems to have a problem.

Here I can see three options.
1) Put some extra air bricks in the external walls, although it is
already fairly well ventilated.
2) Take off the concrete and a couple of courses of bricks (then clear
out any rubble), insert some sort of DPC, rebuild (with DPC also
between the hearth and the internal wall).
3) Leave it all alone and hope that the presence of a fire will dry it
out.

Thanks for your help!

You are suffering a common problem - your victorian house was never intended
to be damp proofed. Damp will not have been a problem before it was
attacked with modern building practices as the original materials would have
been breathable (ie lime mortar/plaster) and the house would have been
adequately ventillated (ie draughts and chimneys) and heated with open
fires.

The fact that DPC and modern cement based plasters and renders have been
used will just force and concentrate the moisture (which would have just
evaporated away) into non damp proof areas. In the case of the internal
wall the moisture is exhibiting itself at the top of the membrane. Ground
floor hearths are often a problem when solid (earth) floors are replaced
with concrete & membrane as its not easy to continue the membrane under the
hearth without ripping it all out.

If you asked these questions of somebody knowledgeable in period properties
they would suggest that all cement based renders/plasters be removed and
replaced with lime mortars/renders/plasters. All attempts at damp proofing
be removed, and breathable floor and wall coverings be used. But that would
probably be very expensive.

As far as the internal wall is concerned, I would remove the plaster, remove
the 1m high membrane and dry line the wall. Plasterboard attached to
treated wooden frame. Vapour check or even insulated plasterboard might be
a better idea.

As far as the hearth is concerned ???? Is it on a solid floor ??

Damp proofing a house after it has been built is very difficult as all youll
ever do is move the problem somewhere else and as I said your Victorian
house didnt need to be damp proofed.

"Andrew Collins" wrote in message
...
I have a Victorian townhouse, it appears to have been built without a
DPC at all, there isn't even a slate one I can find.

The problem I have is that the previous owners have had a chemical
damp proof course installed over much of the house and it hasn't
entirely worked. Some areas that have no DPC have no damp problem at
all... Most of the house is fine, but there are two areas (both
internal), one of plain wall and one around a hearth where there is
damp and chemical DPC.

I suspect the problem is very minor but is being made a lot worse by
the fact that a membrane has been fitted between the brick and the
plaster up to a height of 1m. This means that there is a line of damp
at 1m accross my wall.

Now, I am not sure if all the damp around the hearth is rising damp, I
suspect it might simply be rain coming down the chimney (not capped,
it fell off a year or so ago).

For the rest which is rising damp, I can see two, maybe three courses
of action.
1) Put in an extra layer of chemical DPC.
2) As I suspect the damp isn't serious, remove the membrane backed
plaster and simply paster over it with regular plaster, hoping that
the damp will simply evaporate.
3) Go along brick by brick, and somehow install a membrane DPC.

I'm replacing the fireplace around one area, so am tempted by option 2
there. For the wall it has to be 1 or 3.

Is option 3 viable? Is it ever done? I know it would be very time
consuming but I have a lot of time!

Now, next issue is the hearth itself, I'm fairly sure this is rising
damp and not from the chimney. Oddly enough, only the room side wall
of the hearth seems to have a problem.

Here I can see three options.
1) Put some extra air bricks in the external walls, although it is
already fairly well ventilated.
2) Take off the concrete and a couple of courses of bricks (then clear
out any rubble), insert some sort of DPC, rebuild (with DPC also
between the hearth and the internal wall).
3) Leave it all alone and hope that the presence of a fire will dry it
out.

Thanks for your help!

Andrew Collins wrote in message ...
I suspect the problem is very minor but is being made a lot worse by
the fact that a membrane has been fitted between the brick and the
plaster up to a height of 1m. This means that there is a line of damp
at 1m accross my wall.

This could be coming down rather than up.
I and others have spouted quite a lot on the "damp" subject in the past as a
Google search will reveal. I suggest you look at that first.
It's a major problem in brick built Victorian houses and there is really no
quick fix. After years of pondering my own problems, I'm coming to the
conclusion that you can't stop it getting into the wall and the best you can
hope for is to stop it reaching your interior decorations.

In article ,
"stuart noble" writes:

Andrew Collins wrote in message ...
I suspect the problem is very minor but is being made a lot worse by
the fact that a membrane has been fitted between the brick and the
plaster up to a height of 1m. This means that there is a line of damp
at 1m accross my wall.

This could be coming down rather than up.
I and others have spouted quite a lot on the "damp" subject in the past as a
Google search will reveal. I suggest you look at that first.
It's a major problem in brick built Victorian houses and there is really no
quick fix. After years of pondering my own problems, I'm coming to the
conclusion that you can't stop it getting into the wall and the best you can
hope for is to stop it reaching your interior decorations.

I've done a few things, which has stopped it, but I don't know
which was responsible.

Where wall was damp and I thought I might have rising or
penetrating damp near ground level, I have replastered with a
sand/cement/lime/waterproofer scratch coat and regular finish
coat. This has stopped the inside surface of the wall being
damp.

I have also installed central heating. There were a couple of
areas of north facing walls where damp was higher up, and I
positioned radiators in those areas of the rooms. I suspect
the damp was probably condensation, but it's not impossible
that it was penetrating damp. I just reskimmed over the
original plaster in these areas, and they have stayed dry too
since.

--
Andrew Gabriel

"Andrew Collins" wrote in message
...
I have a Victorian townhouse, it appears to have been built without a
DPC at all, there isn't even a slate one I can find.

The problem I have is that the previous owners have had a chemical
damp proof course installed over much of the house and it hasn't
entirely worked. Some areas that have no DPC have no damp problem at
all... Most of the house is fine, but there are two areas (both
internal), one of plain wall and one around a hearth where there is
damp and chemical DPC.

I suspect the problem is very minor but is being made a lot worse by
the fact that a membrane has been fitted between the brick and the
plaster up to a height of 1m. This means that there is a line of damp
at 1m accross my wall.

Now, I am not sure if all the damp around the hearth is rising damp, I
suspect it might simply be rain coming down the chimney (not capped,
it fell off a year or so ago).

For the rest which is rising damp, I can see two, maybe three courses
of action.
1) Put in an extra layer of chemical DPC.
2) As I suspect the damp isn't serious, remove the membrane backed
plaster and simply paster over it with regular plaster, hoping that
the damp will simply evaporate.
3) Go along brick by brick, and somehow install a membrane DPC.

I'm replacing the fireplace around one area, so am tempted by option 2
there. For the wall it has to be 1 or 3.

Is option 3 viable? Is it ever done? I know it would be very time
consuming but I have a lot of time!

Now, next issue is the hearth itself, I'm fairly sure this is rising
damp and not from the chimney. Oddly enough, only the room side wall
of the hearth seems to have a problem.

Here I can see three options.
1) Put some extra air bricks in the external walls, although it is
already fairly well ventilated.
2) Take off the concrete and a couple of courses of bricks (then clear
out any rubble), insert some sort of DPC, rebuild (with DPC also
between the hearth and the internal wall).
3) Leave it all alone and hope that the presence of a fire will dry it
out.

What I did was a more belt and braces solution. It certainly wasn`t the
cheapest way of sorting the problem out but it gives me piece of mind and
makes the room usable rather than a damp hole.
My application was a basement - so slightly different from you but some of
the walls were internal and had no DPC - therefore no penetrating damp, just
rising damp.
I used a damp proof membrane from a company called Delta Membranes. They
sell to trade, DIY allsorts.. It basically is a plastic studded sheet (quite
thick) that is secured to the wall with plastic 'plugs'. The studs allow the
wall to breathe behind the membrane so the damp problem isn`t moved
elsewhere (which was important in my case).
Depending upon what type of membrane you install, you can either plaster
directly on top or dry line. The good thing was also that I could puncture
the membrane afterwoods if i needed to fix anything to the wall - all I
needed to do was squirt a bit of mastic in the hole along with the fixing.
So far I`m impressed with its application, although drilling holes every 10
inches for the plugs to hold the membrane to the wall is a right pain in the
ass and the whole job is quite labour intensive.
It cost me approx 9 quid per metre sq which covers all the materials, not
cheep but the best solution in my case.
You can find their site at http://www.deltamembranes.co.uk if you want to
check this method out.

John

On Wed, 29 Oct 2003 11:27:07 -0000, "Andy Farrall"
wrote:

As far as the internal wall is concerned, I would remove the plaster, remove
the 1m high membrane and dry line the wall. Plasterboard attached to
treated wooden frame. Vapour check or even insulated plasterboard might be
a better idea.

Aah... hadn't though of that (I feel really thick now).

As far as the hearth is concerned ???? Is it on a solid floor ??

No, its the original wooden one.

The problem is at the front (room side) two corners of the hearth.
They are damp. There is a piece of concrete accross the top of the
hearth that looks non-orginal. The fireplace had a disused (condemned
by CORGI) back boiler in it when we moved in and the hearth had been
carpetted over. I suspect that when the original fireplace was removed
someone took off the hearth tiles and just concreted back to the floor
level, presumably doing something to cause a damp problem when they
did it. I'm not quite sure what they could have done though.

As it's the corners it does occur to me that they may have put a
membrane under the top layer of concrete and that it may have become
damaged or bridged around the corners.

If the worst comes to the worst we can just take the concrete and a
couple of layers of bricks off and floorboard over it, but I'd like to
keep the original hearth if I can (and put a decent fireplace back
in).

I think the first step is to remove the top laye of concrete and see
what is what underneath.


Damp proofing a house after it has been built is very difficult as all youll
ever do is move the problem somewhere else and as I said your Victorian
house didnt need to be damp proofed.

Mortgage companies don't seem to understand this though, surveyors go
round with electronic devices that measure the slightest bit of damp
in the walls and the mortgage company throws a wobbler.

We had enormous trouble getting the mortgage we wanted because
apparently there is damp just about everywhere in the house. Its only
a problem in those two places though.

Thanks for your help (everyone), most appeciated.

Andrew Gabriel wrote in message ...

Where wall was damp and I thought I might have rising or
penetrating damp near ground level, I have replastered with a
sand/cement/lime/waterproofer scratch coat and regular finish
coat. This has stopped the inside surface of the wall being
damp.

I've often wondered whether it's the re-plastering, rather than the dpc
injection that normally accompanies it, that does the job.

I have also installed central heating. There were a couple of
areas of north facing walls where damp was higher up, and I
positioned radiators in those areas of the rooms. I suspect
the damp was probably condensation, but it's not impossible
that it was penetrating damp. I just reskimmed over the
original plaster in these areas, and they have stayed dry too
since.

We've had quite a long dry spell though......

I think the first step is to remove the top laye of concrete and see
what is what underneath.

Yes, and replace with a breathable material (ie lime based). The problem
will be where the floorboards meet the hearth - the wood may absorb moisture
through capilliary action. Could just make sure the edges of the
floorboards are "sealed" with beeswax/turps polish or varnish (depending on
whats on there already). Try asking on the discussion forum at
www.periodproperty.co.uk there are lots of knowledgeable people on there.

Mortgage companies don't seem to understand this though, surveyors go
round with electronic devices that measure the slightest bit of damp
in the walls and the mortgage company throws a wobbler.

Absolutely - ******* !! Mortgage companies and most surveyors have no idea
about period property and are the cause of alot of problems (ie insisting on
dpc etc). There are mortgage companies that specialise in period property
but as far as I know they charge a premium. The survey on my house said
that there is damp everywhere but fortunately the mortage company did not
retain any money they just said to sort it out. This we did by removing
lino from quarry tile on earth floors, removing small patches of cement
based renders/plaster where repairs had been made, removing non breathable
wall coverings etc. One winter, one summer and lots of coal fires later we
have no damp.

Never trust anyone with an electronic damp meter - 9 times out of 10 they
are measuring condensation anyway. The only way to determine if there is
damp in a wall (for example) is to take core samples.

"Andrew Collins" wrote in message
...
I have a Victorian townhouse, it appears to have been built without a
DPC at all, there isn't even a slate one I can find.

The problem I have is that the previous owners have had a chemical
damp proof course installed over much of the house and it hasn't
entirely worked. Some areas that have no DPC have no damp problem at
all... Most of the house is fine, but there are two areas (both
internal), one of plain wall and one around a hearth where there is
damp and chemical DPC.


Hi Andrew. There are loads of possible causes of damp. The fashion
nowadays is to believe in one approach that will wham bam cure the
lot, but really this is usually not the solution with these old
houses. More often it seems to be a case of going round and looking
for all the assorted sources of dampness and dealing with them all.
Then the place will dry up in almost every case.

An open chimney is obviously going to let quite a bit of water come
in, I'd look into the possibility of one of those rain shedding cowls.

Even if it turned out you have another damp problem, that will still
help or often even cure the other problem. Why? Victorian houses are
basically like sieves, water comes in, ventilation goes through, damp
is evaporated out. So if you halve your water input, your level of
dampness drops to the point of being normal, and your otherwise damp
spots dry out well enough not to cause any further problem.


Regards, NT

N. Thornton wrote in message ...
An open chimney is obviously going to let quite a bit of water come
in, I'd look into the possibility of one of those rain shedding cowls.
In a 9" wall you often only have 4" between the elements and the inside of
the chimney. I don't know how well soot retains moisture but it would help
explain why chimney breasts are often affected more than the adjacent wall.

"stuart noble" wrote in message
...

N. Thornton wrote in message ...
An open chimney is obviously going to let quite a bit of water come
in, I'd look into the possibility of one of those rain shedding cowls.
In a 9" wall you often only have 4" between the elements and the inside of
the chimney. I don't know how well soot retains moisture but it would help
explain why chimney breasts are often affected more than the adjacent
wall.



It's not just the mechanical retention of water in the soot, the sulpher
compounds that are produced when coal burns leave salts in the soot that are
hygroscopic - these are absorbed into the brickwork and cause problems for
years after the flue has been used for open fires. For this reason avoid
using reclaimed bricks that have come from chimneys as they will cause
problems even when built into a new wall.

Andrew Mawson

In article ,
stuart noble wrote:
I've often wondered whether it's the re-plastering, rather than the dpc
injection that normally accompanies it, that does the job.

If the house has solid 9" brick walls made out of yellow stocks, the
bricks themselves are porous. Try weighing a dry one then leave it soaking
in a bucket of water, then weigh again...

However, try building a test wall say 4 courses high in an old steel bath
etc. Fill the bath to below the height of the first course to simulate
bricks sitting on damp earth and leave. You'll find the damp doesn't rise
to the top. This is why the houses all should have a raised ground floor,
and either a cellar or the ground level reduced within the walls. Most
will also have no plaster at floor level, but a high skirting board spaced
off the wall. So any so called 'rising damp' never makes it to the plaster.

The trick is to try and minimise the amount of rain etc that lands on the
bricks. Good guttering etc is essential, as is good pointing, flashing
etc. At ground level, if you have concrete right up to the walls it's a
good idea to cut this about 9" short and fill with gravel to allow a soak
away. It will also stop heavy rain splashing onto the bricks. A mortar
render a couple of courses high at ground level is also common, but I'd
say this is more cosmetic and to protect the bricks from damage.

--
*Being healthy is merely the slowest possible rate at which one can die.

Dave Plowman London SW 12
RIP Acorn

Andrew Mawson wrote in message ...
It's not just the mechanical retention of water in the soot, the sulpher
compounds that are produced when coal burns leave salts in the soot that
are
hygroscopic - these are absorbed into the brickwork and cause problems for
years after the flue has been used for open fires. For this reason avoid
using reclaimed bricks that have come from chimneys as they will cause
problems even when built into a new wall.
Thanks, Andrew. Interesting stuff.

Dave Plowman wrote in message ...
If the house has solid 9" brick walls made out of yellow stocks, the
bricks themselves are porous. Try weighing a dry one then leave it soaking
in a bucket of water, then weigh again...
Sure, but they're still pretty dense compared to the old mortar between
them, which IME is the weak link. I have often wondered about the BRE
research (which you seem to have re-created in your metal bath:-)) . They
build a wall from yellow stocks and can't get water to travel up it, but do
they tell you anything about the mortar they used? I wouldn't go as far as
to say there's no such thing as rising damp in brick, having seen it with my
own eyes this week on a party wall in the middle of a house, but I still
blame the mortar, I think....


However, try building a test wall say 4 courses high in an old steel bath
etc. Fill the bath to below the height of the first course to simulate
bricks sitting on damp earth and leave. You'll find the damp doesn't rise
to the top. This is why the houses all should have a raised ground floor,
and either a cellar or the ground level reduced within the walls. Most
will also have no plaster at floor level, but a high skirting board spaced
off the wall. So any so called 'rising damp' never makes it to the plaster.

The trick is to try and minimise the amount of rain etc that lands on the
bricks. Good guttering etc is essential, as is good pointing, flashing
etc. At ground level, if you have concrete right up to the walls it's a
good idea to cut this about 9" short and fill with gravel to allow a soak
away. It will also stop heavy rain splashing onto the bricks. A mortar
render a couple of courses high at ground level is also common, but I'd
say this is more cosmetic and to protect the bricks from damage.

--
*Being healthy is merely the slowest possible rate at which one can die.

Dave Plowman London SW 12
RIP Acorn

"stuart noble" wrote in message ...
N. Thornton wrote in message ...
An open chimney is obviously going to let quite a bit of water come
in,

To be more precise, about 56" a year of water! Worth losing I'd think.


Regards, NT