A plasterer has just finished a chemical DPC at my house and
replastered. One of the walls was really bad but it's all done now.

This same wall, a few days later is still damp (he used Limelite
Renovation for both layers). I'm just wondering how long I should wait
until for this patch to dry out.

Is there any paint-on damp proofing that I could use to cure this
remaining problem?

Thanks,

Ed.

Ed_Zep wrote:
A plasterer has just finished a chemical DPC at my house and
replastered. One of the walls was really bad but it's all done now.

This same wall, a few days later is still damp (he used Limelite
Renovation for both layers). I'm just wondering how long I should wait
until for this patch to dry out.

Could be damp for a while, at least a month, depending on the thickness of
the plaster and the weather etc. Did the guy not tell you how long to wait?

Rob

He just said "give it a while". Hmmmm...

I did notice that the bricks were still damp before he replastered. It
happened to be the worst bit out of the lot, anyway. The bricks above
it had turned white from the treatment and seemed mostly dry. The ones
lower down are the ones still wet.

Is it worth gently heating the room to see if I can find out whether
the treatment's worked?

Supposing it didn't work is it possible to drill into the wall and
reapply some more of the DPC chemical without having to knock off the
plaster?

Cheers, Ed.


Rob Summers wrote:
Ed_Zep wrote:
A plasterer has just finished a chemical DPC at my house and
replastered. One of the walls was really bad but it's all done now.

This same wall, a few days later is still damp (he used Limelite
Renovation for both layers). I'm just wondering how long I should wait
until for this patch to dry out.

Could be damp for a while, at least a month, depending on the thickness of
the plaster and the weather etc. Did the guy not tell you how long to wait?

Rob

In article . com,
"Ed_Zep" writes:
A plasterer has just finished a chemical DPC at my house and
replastered. One of the walls was really bad but it's all done now.

Oh dear. Most injected DPC are just a method for ripping off
punters. It's very rare that they fix any kind of damp.

This same wall, a few days later is still damp

Not surprising. A damp wall will take weeks to dry out, but
if the cause of the damp was wrongly identified, it will never
dry out.

(he used Limelite
Renovation for both layers). I'm just wondering how long I should wait
until for this patch to dry out.

I don't know this plaster, but a full scratch and finish coat will
take many days to dry out anyway, plus however long the wall takes
to dry out.

Is there any paint-on damp proofing that I could use to cure this
remaining problem?

No, at least not without accurately identifying the cause of the
damp, and not at all if it's condensation (which is a very
common cause).

--
Andrew Gabriel

Ed_Zep wrote:

A plasterer has just finished a chemical DPC at my house and
replastered. One of the walls was really bad but it's all done now.

ouch. From your comments it sounds like you've been got.


This same wall, a few days later is still damp (he used Limelite
Renovation for both layers). I'm just wondering how long I should wait
until for this patch to dry out.

just forget about it. If its still damp in 6 months, the cause hasnt
been fixed. Brick walls take months to dry out. At this point theres no
knowing if the dpc man did anything that would make the wall dry out,
only time will tell. Often they remove soil and vegetation from the
outer side of the wall, which fixes the problem.


Is there any paint-on damp proofing that I could use to cure this
remaining problem?

Painting things on wont draw the water out. Quite the opposite, any
barrier only slows evaporation down.


He just said "give it a while". Hmmmm...

I did notice that the bricks were still damp before he replastered. It
happened to be the worst bit out of the lot, anyway. The bricks above
it had turned white from the treatment and seemed mostly dry. The ones
lower down are the ones still wet.

Is it worth gently heating the room to see if I can find out whether
the treatment's worked?

I see no connection between the 2.


Supposing it didn't work is it possible to drill into the wall and
reapply some more of the DPC chemical without having to knock off the
plaster?

sure, but entirely pointless. A DPC has nothing to do with damp
problems in almost all cases.


NT

So can anyone tell me how to diagnose a damp interior wall please?

Can condensation really be the cause of very damp bricks. What is the
standard solution for that?

Thanks,

Ed.


Andrew Gabriel wrote:
In article . com,
"Ed_Zep" writes:
A plasterer has just finished a chemical DPC at my house and
replastered. One of the walls was really bad but it's all done now.

Oh dear. Most injected DPC are just a method for ripping off
punters. It's very rare that they fix any kind of damp.

This same wall, a few days later is still damp

Not surprising. A damp wall will take weeks to dry out, but
if the cause of the damp was wrongly identified, it will never
dry out.

(he used Limelite
Renovation for both layers). I'm just wondering how long I should wait
until for this patch to dry out.

I don't know this plaster, but a full scratch and finish coat will
take many days to dry out anyway, plus however long the wall takes
to dry out.

Is there any paint-on damp proofing that I could use to cure this
remaining problem?

No, at least not without accurately identifying the cause of the
damp, and not at all if it's condensation (which is a very
common cause).

--
Andrew Gabriel

"Ed_Zep" wrote:
So can anyone tell me how to diagnose a damp interior wall please?

The only DIY method I know is to fix a small piece of glass onto the plaster
with a circle of putty or plasticine so that there is a gap between the
plaster and the glass. If there is moisture in the trapped air then it will
condense out on the inner surface of the glass. This test will confirm damp
but doesn't tell you its source. But as your walls have been re-plastered
very recently there is no point in doing this until the new plaster has had
chance to dry out. Didn't the installer tell you not to paint/redecorate for
at least 6 weeks?

Can condensation really be the cause of very damp bricks.

Seems unlikely. Condensation often causes damp plaster and mould growth.

What is the
standard solution for that?

Well, there's http://www.axp.mdx.ac.uk/~john49/dampfaq.htm
Scroll down to condensation.

And there's what the damp proofing companies will tell you, which may or may
not be correct.

In article . com,
"Ed_Zep" writes:
So can anyone tell me how to diagnose a damp interior wall please?

Firstly, what made you think it was damp to start with?
What times of the year was it more evident?
What's the construction of the wall? (type of bricks, mortar, thickness?)
What's on each side of the wall? (type of finish, room, outdoors?)
What's on the top of the wall?
Any chimney flues?

Can condensation really be the cause of very damp bricks. What is the

Yes.

standard solution for that?

Ventilation, avoiding uneven heating, avoiding discharge of moisture.

--
Andrew Gabriel

On 03 Aug 2006 07:04:42 GMT, (Andrew Gabriel)
wrote:

|In article . com,
| "Ed_Zep" writes:

|
| Can condensation really be the cause of very damp bricks. What is the
|
|Yes.
|
| standard solution for that?
|
|Ventilation, avoiding uneven heating, avoiding discharge of moisture.

Better insulate the cavity, so the inside leaf gets warm, and condensation
does not form.
--
Dave Fawthrop dave hyphenologist co uk Google Groups is IME the *worst*
method of accessing usenet. GG subscribers would be well advised get a
newsreader, say Agent, and a newsserver, say news.individual.net. These
will allow them: to see only *new* posts, a killfile, and other goodies.

Ed_Zep wrote:
A plasterer has just finished a chemical DPC at my house and
replastered. One of the walls was really bad but it's all done now.

This same wall, a few days later is still damp (he used Limelite
Renovation for both layers). I'm just wondering how long I should wait
until for this patch to dry out.

Is there any paint-on damp proofing that I could use to cure this
remaining problem?

Thanks,

Ed.

Uh-oh. Another one falls victim to the chemical DPC scam....

Could that be done without replastering and/or is it straightforward?

Dave Fawthrop wrote:
On 03 Aug 2006 07:04:42 GMT, (Andrew Gabriel)
wrote:

|In article . com,
| "Ed_Zep" writes:

|
| Can condensation really be the cause of very damp bricks. What is the
|
|Yes.
|
| standard solution for that?
|
|Ventilation, avoiding uneven heating, avoiding discharge of moisture.

Better insulate the cavity, so the inside leaf gets warm, and condensation
does not form.
--
Dave Fawthrop dave hyphenologist co uk Google Groups is IME the *worst*
method of accessing usenet. GG subscribers would be well advised get a
newsreader, say Agent, and a newsserver, say news.individual.net. These
will allow them: to see only *new* posts, a killfile, and other goodies.

"Ed_Zep" wrote:
Could that be done without replastering and/or is it straightforward?

Cavity wall insulation is normally blown in through holes drilled in the
outside wall. Normally straightforward subject to a survey and grants are
available.

In article . com,
Ed_Zep wrote:
A plasterer has just finished a chemical DPC at my house and
replastered. One of the walls was really bad but it's all done now.

This same wall, a few days later is still damp (he used Limelite
Renovation for both layers). I'm just wondering how long I should wait
until for this patch to dry out.

Is there any paint-on damp proofing that I could use to cure this
remaining problem?

The usual trick with a chemical DPC is to render the inside with
waterproof mortar before the plaster skim. Which does, of course, get rid
of damp showing on the inside of that part of the wall. But doesn't cure
the cause - anymore than a chemical DPC does.

--
*Forget the Joneses, I keep us up with the Simpsons.

Dave Plowman London SW
To e-mail, change noise into sound.

This is an internal wall, though.


Phil Anthropist wrote:
"Ed_Zep" wrote:
Could that be done without replastering and/or is it straightforward?

Cavity wall insulation is normally blown in through holes drilled in the
outside wall. Normally straightforward subject to a survey and grants are
available.

Ed_Zep wrote:

This is an internal wall, though.

Then it's either rising damp which the dpc should cure (claim under the
guarantee if it doesn't dry out in the specified time). Or you have a
plumbing leak. Is this a kitchen or what?

On 3 Aug 2006 01:24:46 -0700, "Ed_Zep" wrote:

|Could that be done without replastering and/or is it straightforward?
|
|Dave Fawthrop wrote:
| On 03 Aug 2006 07:04:42 GMT, (Andrew Gabriel)
| wrote:
|
| |In article . com,
| | "Ed_Zep" writes:
|
| |
| | Can condensation really be the cause of very damp bricks. What is the
| |
| |Yes.
| |
| | standard solution for that?
| |
| |Ventilation, avoiding uneven heating, avoiding discharge of moisture.
|
| Better insulate the cavity, so the inside leaf gets warm, and condensation
| does not form.

It is very straight forward, it is done from the outside by commercial
companies. The government has offers if you are on benefit etc. You just
get three quotes and take the lowest, or best.
--
Dave Fawthrop dave hyphenologist co uk Google Groups is IME the *worst*
method of accessing usenet. GG subscribers would be well advised get a
newsreader, say Agent, and a newsserver, say news.individual.net. These
will allow them: to see only *new* posts, a killfile, and other goodies.

On 3 Aug 2006 02:26:12 -0700, "Ed_Zep" wrote:

|This is an internal wall, though.
|
|
|Phil Anthropist wrote:
| "Ed_Zep" wrote:
| Could that be done without replastering and/or is it straightforward?
|
| Cavity wall insulation is normally blown in through holes drilled in the
| outside wall. Normally straightforward subject to a survey and grants are
| available.

Then insulation will not work.
--
Dave Fawthrop dave hyphenologist co uk Google Groups is IME the *worst*
method of accessing usenet. GG subscribers would be well advised get a
newsreader, say Agent, and a newsserver, say news.individual.net. These
will allow them: to see only *new* posts, a killfile, and other goodies.

Stuart Noble wrote:
Ed_Zep wrote:

This is an internal wall, though.

Then it's either rising damp which the dpc should cure (claim under the
guarantee if it doesn't dry out in the specified time). Or you have a
plumbing leak. Is this a kitchen or what?


Causes of damp on internal walls, in order of likelihood:

1. condensation. Cause: interior RH too high. Solution: find cause/s of
high RH and fix em.

2. Faulty roof or rainwater goods dumping water onto the wall.
Solution: clear gutters and hoppers, check rain drainage works ok, or
fix roof.

3. Salt contamination: this tends to happen to chimneys mostly, but can
also result from iron pipe fixings or spillages. Solution: remove and
replace plaster

4. Peeing: animal or small child peeing on wall. Solution: retrain.

5. Rising damp: it does exist but is rare. If every other cause has
been ruled out, and every necessary measure taken, inserting a dpc just
might work. Almost all rising damp diagnoses are false.


NT

wrote:
Stuart Noble wrote:
Ed_Zep wrote:

This is an internal wall, though.
Then it's either rising damp which the dpc should cure (claim under the
guarantee if it doesn't dry out in the specified time). Or you have a
plumbing leak. Is this a kitchen or what?


Causes of damp on internal walls, in order of likelihood:

1. condensation. Cause: interior RH too high. Solution: find cause/s of
high RH and fix em.

Not very likely in the current weather conditions I'd say and, even in
winter, usually due to a lack of heating.

2. Faulty roof or rainwater goods dumping water onto the wall.
Solution: clear gutters and hoppers, check rain drainage works ok, or
fix roof.

Possible if there's a leaking valley or something on the roof but that
should be obvious at the top of the wall

3. Salt contamination: this tends to happen to chimneys mostly, but can
also result from iron pipe fixings or spillages. Solution: remove and
replace plaster

4. Peeing: animal or small child peeing on wall. Solution: retrain.

5. Rising damp: it does exist but is rare. If every other cause has
been ruled out, and every necessary measure taken, inserting a dpc just
might work. Almost all rising damp diagnoses are false.

Agreed, but rising damp has to be considered on a wet internal wall in
the middle of summer. I'd be looking for a leak but we don't as yet know
the OP's setup.


NT

Yep, it's a kitchen but the damp is in a about four different places
and not adjacent.

I live towards the bottom of a steep hill. Could it be water underneath
flowing downward?


Stuart Noble wrote:
Ed_Zep wrote:

This is an internal wall, though.

Then it's either rising damp which the dpc should cure (claim under the
guarantee if it doesn't dry out in the specified time). Or you have a
plumbing leak. Is this a kitchen or what?

Ed_Zep wrote:
Yep, it's a kitchen but the damp is in a about four different places
and not adjacent.

I live towards the bottom of a steep hill. Could it be water underneath
flowing downward?


If this is ground floor and the damp doesn't affect the external walls,
you have to be looking at some kind of rising damp or a leak. Either way
the damp should be worse at the bottom and not go any higher than 1
metre. Is this a solid floor?

Most of the ground floor is wooden floor boards but there are two tiled
floors where I guess it seems to be a solid floor underneath.


Stuart Noble wrote:
Ed_Zep wrote:
Yep, it's a kitchen but the damp is in a about four different places
and not adjacent.

I live towards the bottom of a steep hill. Could it be water underneath
flowing downward?


If this is ground floor and the damp doesn't affect the external walls,
you have to be looking at some kind of rising damp or a leak. Either way
the damp should be worse at the bottom and not go any higher than 1
metre. Is this a solid floor?

And yes, the damp seems worse just above the skirting board.


Stuart Noble wrote:
Ed_Zep wrote:
Yep, it's a kitchen but the damp is in a about four different places
and not adjacent.

I live towards the bottom of a steep hill. Could it be water underneath
flowing downward?


If this is ground floor and the damp doesn't affect the external walls,
you have to be looking at some kind of rising damp or a leak. Either way
the damp should be worse at the bottom and not go any higher than 1
metre. Is this a solid floor?

Ed_Zep wrote:
Most of the ground floor is wooden floor boards but there are two tiled
floors where I guess it seems to be a solid floor underneath.


Stuart Noble wrote:
Ed_Zep wrote:
Yep, it's a kitchen but the damp is in a about four different places
and not adjacent.

I live towards the bottom of a steep hill. Could it be water underneath
flowing downward?

If this is ground floor and the damp doesn't affect the external walls,
you have to be looking at some kind of rising damp or a leak. Either way
the damp should be worse at the bottom and not go any higher than 1
metre. Is this a solid floor?


If the damp is above the tiled bits that you assume are solid, I would
guess there is no dpc under the concrete (usual in older houses). If the
floor was latex screeded before the tiles went down, the water could be
soaking up into the wall as the only means of escape. If this is the
case then your dpc injection should stop it. If not get the firm back to
re-inject. Maybe it will dry out in a month or so. It should at least be
improving by now. Try drawing round the damp patches with a pencil and
see if they're shrinking day by day. Are the floor tiles dry at the edges?
If this was winter I might be testing for condensation by now but I just
can't see the surfaces being cool enough in the middle of a hot summer

Ed_Zep wrote:
And yes, the damp seems worse just above the skirting board.

it will be, as the bottom of the wall is in contact with the colder
wet/damp ground, plus the underfloor void in the case of suspended
floors, and being the coldest bit of wall condensation will happen
there first. If youve got condensing your RH is too high.

NT

Stuart Noble wrote:
Ed_Zep wrote:
Most of the ground floor is wooden floor boards but there are two tiled
floors where I guess it seems to be a solid floor underneath.


Stuart Noble wrote:
Ed_Zep wrote:
Yep, it's a kitchen but the damp is in a about four different places
and not adjacent.

I live towards the bottom of a steep hill. Could it be water underneath
flowing downward?

If this is ground floor and the damp doesn't affect the external walls,
you have to be looking at some kind of rising damp or a leak. Either way
the damp should be worse at the bottom and not go any higher than 1
metre. Is this a solid floor?


If the damp is above the tiled bits that you assume are solid, I would
guess there is no dpc under the concrete (usual in older houses). If the
floor was latex screeded before the tiles went down, the water could be
soaking up into the wall as the only means of escape. If this is the
case then your dpc injection should stop it. If not get the firm back to
re-inject. Maybe it will dry out in a month or so. It should at least be
improving by now. Try drawing round the damp patches with a pencil and
see if they're shrinking day by day. Are the floor tiles dry at the edges?
If this was winter I might be testing for condensation by now but I just
can't see the surfaces being cool enough in the middle of a hot summer

The tiles seem dry all over. Have taken your advice and drawn a line
around the patch. I guess the real test will be in winter.

Ed_Zep wrote:
Stuart Noble wrote:
Ed_Zep wrote:
Most of the ground floor is wooden floor boards but there are two tiled
floors where I guess it seems to be a solid floor underneath.


Stuart Noble wrote:
Ed_Zep wrote:
Yep, it's a kitchen but the damp is in a about four different places
and not adjacent.

I live towards the bottom of a steep hill. Could it be water underneath
flowing downward?

If this is ground floor and the damp doesn't affect the external walls,
you have to be looking at some kind of rising damp or a leak. Either way
the damp should be worse at the bottom and not go any higher than 1
metre. Is this a solid floor?
If the damp is above the tiled bits that you assume are solid, I would
guess there is no dpc under the concrete (usual in older houses). If the
floor was latex screeded before the tiles went down, the water could be
soaking up into the wall as the only means of escape. If this is the
case then your dpc injection should stop it. If not get the firm back to
re-inject. Maybe it will dry out in a month or so. It should at least be
improving by now. Try drawing round the damp patches with a pencil and
see if they're shrinking day by day. Are the floor tiles dry at the edges?
If this was winter I might be testing for condensation by now but I just
can't see the surfaces being cool enough in the middle of a hot summer

The tiles seem dry all over. Have taken your advice and drawn a line
around the patch. I guess the real test will be in winter.

It's a tough one this, but you can probably achieve more by observation
and a bit of logic than some builder coming in cold and hazarding a
guess. The fact that it's an internal wall rules out a lot of the
potential causes

Stuart Noble wrote:

It's a tough one this, but you can probably achieve more by observation
and a bit of logic than some builder coming in cold and hazarding a
guess. The fact that it's an internal wall rules out a lot of the
potential causes

yes, leaving only 2 likely options.


NT

Leaking pipe or real rising damp?



wrote:
Stuart Noble wrote:

It's a tough one this, but you can probably achieve more by observation
and a bit of logic than some builder coming in cold and hazarding a
guess. The fact that it's an internal wall rules out a lot of the
potential causes

yes, leaving only 2 likely options.


NT

Ed_Zep wrote:
wrote:
Stuart Noble wrote:

It's a tough one this, but you can probably achieve more by observation
and a bit of logic than some builder coming in cold and hazarding a
guess. The fact that it's an internal wall rules out a lot of the
potential causes

yes, leaving only 2 likely options.

Leaking pipe or real rising damp?

leaking pipe or condensation, rising damp is highly unlikely.


NT

Phil wrote:
Ed_Zep wrote:
A plasterer has just finished a chemical DPC at my house and
replastered. One of the walls was really bad but it's all done now.

This same wall, a few days later is still damp (he used Limelite
Renovation for both layers). I'm just wondering how long I should wait
until for this patch to dry out.

Is there any paint-on damp proofing that I could use to cure this
remaining problem?

Thanks,

Ed.

Uh-oh. Another one falls victim to the chemical DPC scam....

It's very obvious that a lot of people are sceptical about rising damp
and chemical DPC to the point that they are suggesting gross
incompetence and/or fraudulent activity on behlaf of the companies
offering this service.

So I have a couple of questions:

1) Is the actual method of injecting a chemical DPC flawed for designed
purpose? i.e. in controlled conditions where you can create an
environment in which rising damp is manifested is it physically
possible to stop it by injecting the wall?

2) Has anyone been persued, investigated or prosecuted for offering
fraudulent services with regard to injecting chemical DPC? If not whay
not, given peoples insistence of the level of con going on?

I've seen damp come up through a floor without a DPC but don't think
I've ever seen proper rising damp in brick work, but then my experience
in this matter is limited.

--
Steve F

Fitz wrote:
Phil wrote:

Uh-oh. Another one falls victim to the chemical DPC scam....

It's very obvious that a lot of people are sceptical about rising damp
and chemical DPC to the point that they are suggesting gross
incompetence and/or fraudulent activity on behlaf of the companies
offering this service.

So I have a couple of questions:

1) Is the actual method of injecting a chemical DPC flawed for designed
purpose? i.e. in controlled conditions where you can create an
environment in which rising damp is manifested is it physically
possible to stop it by injecting the wall?

You need to take one step back here, as experiments to produce rising
damp have repeatedly failed.


2) Has anyone been persued, investigated or prosecuted for offering
fraudulent services with regard to injecting chemical DPC? If not whay
not, given peoples insistence of the level of con going on?

There are 2 answers here. The first is the case of a company that was
injecting water into brickwork instead of dampproofing chemicals. They
did this for an extended period, treating hundreds of properties, and
never had any complaints as a result. What one can conclude from this
is that dpc injection has very little or no effect in curing cases of
damp walls.

The 2nd answer is there are numerous companies in many areas in most
market sectors that routinely offer cures that dont cure anything other
than their own shortage of income. If they can construct and maintain
an argument to bolster their claims, regardless of whether its flawed,
its not technically fraud in the eyes of the law, and they can and
usually do continue trading.


I've seen damp come up through a floor without a DPC but don't think

It will if the floor is in the wet ground, but that in itself is not
rising damp.


NT

In article .com,
"Fitz" writes:
It's very obvious that a lot of people are sceptical about rising damp
and chemical DPC to the point that they are suggesting gross
incompetence and/or fraudulent activity on behlaf of the companies
offering this service.

This comes from research by BRE to demonstrate rising damp
sufficient to cause any problems is extremely unlikely,
and a number of the firms being caught injecting water or
some other useless solvent under the guise of injecting a
damp course.

So I have a couple of questions:

1) Is the actual method of injecting a chemical DPC flawed for designed
purpose? i.e. in controlled conditions where you can create an
environment in which rising damp is manifested is it physically
possible to stop it by injecting the wall?

A properly injected chemical DPC will create a moisture
barrier. It works by coating the internal surfaces in the
brickwork with a water repellant, so they cannot draw water
up by capilarity. It won't stop water coming through if
there's any pressure behind it (i.e. can't be used for
tanking). If the damp was wrongly diagnosed, the chemical
DPC may well just move the damp somewhere else (such as
above the DPC).

2) Has anyone been persued, investigated or prosecuted for offering
fraudulent services with regard to injecting chemical DPC? If not whay
not, given peoples insistence of the level of con going on?

The work is usally accompanied by other things such as
reducing ground level, replastering, etc, and these
probably will make a difference.

I've seen damp come up through a floor without a DPC but don't think
I've ever seen proper rising damp in brick work, but then my experience
in this matter is limited.

--
Andrew Gabriel

wrote:
Ed_Zep wrote:
wrote:
Stuart Noble wrote:

It's a tough one this, but you can probably achieve more by observation
and a bit of logic than some builder coming in cold and hazarding a
guess. The fact that it's an internal wall rules out a lot of the
potential causes

yes, leaving only 2 likely options.

Leaking pipe or real rising damp?

leaking pipe or condensation, rising damp is highly unlikely.

Condensation in a heat wave?

Stuart Noble wrote:
wrote:
Ed_Zep wrote:
wrote:
Stuart Noble wrote:

It's a tough one this, but you can probably achieve more by observation
and a bit of logic than some builder coming in cold and hazarding a
guess. The fact that it's an internal wall rules out a lot of the
potential causes

yes, leaving only 2 likely options.

Leaking pipe or real rising damp?

leaking pipe or condensation, rising damp is highly unlikely.

Condensation in a heat wave?

yes. I suppose you want an explanation. It is temp difference that
causes condensation, not absolute temp (assuming we're talking above
freezing). On a hot day the air can hold a lot of water vapour (the
hotter the air, the more water vapour it can carry). If the hot air has
highish RH, and meets a cold wall on wet ground, the 20C drop can cause
condensation. Although summer condensation is less common than in
winter, it does occur.


NT

wrote:
Stuart Noble wrote:
wrote:
Ed_Zep wrote:
wrote:
Stuart Noble wrote:
It's a tough one this, but you can probably achieve more by observation
and a bit of logic than some builder coming in cold and hazarding a
guess. The fact that it's an internal wall rules out a lot of the
potential causes
yes, leaving only 2 likely options.
Leaking pipe or real rising damp?
leaking pipe or condensation, rising damp is highly unlikely.
Condensation in a heat wave?

yes. I suppose you want an explanation.

Oh yes please, headmaster.

It is temp difference that
causes condensation, not absolute temp (assuming we're talking above
freezing). On a hot day the air can hold a lot of water vapour (the
hotter the air, the more water vapour it can carry). If the hot air has
highish RH, and meets a cold wall on wet ground, the 20C drop can cause
condensation. Although summer condensation is less common than in
winter, it does occur.


I'm perfectly well aware of how condensation occurs thank you, but I've
never seen it during a hot summer, and I doubt you have either.

On Thu, 10 Aug 2006 07:37:09 GMT, Stuart Noble
wrote:

wrote:


|It is temp difference that
| causes condensation, not absolute temp (assuming we're talking above
| freezing). On a hot day the air can hold a lot of water vapour (the
| hotter the air, the more water vapour it can carry). If the hot air has
| highish RH, and meets a cold wall on wet ground, the 20C drop can cause
| condensation. Although summer condensation is less common than in
| winter, it does occur.
|
|
|I'm perfectly well aware of how condensation occurs thank you, but I've
|never seen it during a hot summer, and I doubt you have either.

The temperature of *dry* *internal* walls will approximate to the average
air temperature. (average over several days and both sides of a wall) In a
hot summer temperatures, this average temperature will be high.

I did some experiments and wrote a simulation of temperatures in masonry
walls, subject to air temperature changes, many years ago, but I can no
longer run the code.

As digital probe thermometers are now quite cheap, and available. It
might be a good idea to drill holes in the damp wall and measure the
temperature, at various depths. I will have to think about the effects of
dampness.

--
Dave Fawthrop dave hyphenologist co uk Google Groups is IME the *worst*
method of accessing usenet. GG subscribers would be well advised get a
newsreader, say Agent, and a newsserver, say news.individual.net. These
will allow them: to see only *new* posts, a killfile, and other goodies.

Dave Fawthrop wrote:
On Thu, 10 Aug 2006 07:37:09 GMT, Stuart Noble
wrote:

wrote:


|It is temp difference that
| causes condensation, not absolute temp (assuming we're talking above
| freezing). On a hot day the air can hold a lot of water vapour (the
| hotter the air, the more water vapour it can carry). If the hot air has
| highish RH, and meets a cold wall on wet ground, the 20C drop can cause
| condensation. Although summer condensation is less common than in
| winter, it does occur.
|
|
|I'm perfectly well aware of how condensation occurs thank you, but I've
|never seen it during a hot summer, and I doubt you have either.

The temperature of *dry* *internal* walls will approximate to the average
air temperature. (average over several days and both sides of a wall) In a
hot summer temperatures, this average temperature will be high.

I did some experiments and wrote a simulation of temperatures in masonry
walls, subject to air temperature changes, many years ago, but I can no
longer run the code.

As digital probe thermometers are now quite cheap, and available. It
might be a good idea to drill holes in the damp wall and measure the
temperature, at various depths. I will have to think about the effects of
dampness.


As masonry retains heat, I can't see where this 20C difference in
temperature the honourable gentleman refers to is going to occur. A damp
wall would be colder, but the source of the damp would not then be
condensation.
What was the purpose of your research out of interest?

On Thu, 10 Aug 2006 09:29:53 GMT, Stuart Noble
wrote:

|Dave Fawthrop wrote:
| On Thu, 10 Aug 2006 07:37:09 GMT, Stuart Noble
| wrote:
|
| wrote:
|
|
| |It is temp difference that
| | causes condensation, not absolute temp (assuming we're talking above
| | freezing). On a hot day the air can hold a lot of water vapour (the
| | hotter the air, the more water vapour it can carry). If the hot air has
| | highish RH, and meets a cold wall on wet ground, the 20C drop can cause
| | condensation. Although summer condensation is less common than in
| | winter, it does occur.
| |
| |
| |I'm perfectly well aware of how condensation occurs thank you, but I've
| |never seen it during a hot summer, and I doubt you have either.
|
| The temperature of *dry* *internal* walls will approximate to the average
| air temperature. (average over several days and both sides of a wall) In a
| hot summer temperatures, this average temperature will be high.
|
| I did some experiments and wrote a simulation of temperatures in masonry
| walls, subject to air temperature changes, many years ago, but I can no
| longer run the code.
|
| As digital probe thermometers are now quite cheap, and available. It
| might be a good idea to drill holes in the damp wall and measure the
| temperature, at various depths. I will have to think about the effects of
| dampness.
|
|
|As masonry retains heat, I can't see where this 20C difference in
|temperature the honourable gentleman refers to is going to occur. A damp
|wall would be colder, but the source of the damp would not then be
|condensation.

I would agree.
I could probably sort something out if I knew the, time of day, air
temperature, and the temperature at various depths in the wall.

|What was the purpose of your research out of interest?

Curiosity, and practicing programming, c1978, I had access to a computer
PDP11 03, because of my work. My job spec said that I could program
computers, which I could not do, and I chose to learn in my own dinner
times.
--
Dave Fawthrop dave hyphenologist co uk Google Groups is IME the *worst*
method of accessing usenet. GG subscribers would be well advised get a
newsreader, say Agent, and a newsserver, say news.individual.net. These
will allow them: to see only *new* posts, a killfile, and other goodies.

Stuart Noble wrote:
wrote:
Stuart Noble wrote:
wrote:
Ed_Zep wrote:
wrote:
Stuart Noble wrote:
It's a tough one this, but you can probably achieve more by observation
and a bit of logic than some builder coming in cold and hazarding a
guess. The fact that it's an internal wall rules out a lot of the
potential causes
yes, leaving only 2 likely options.
Leaking pipe or real rising damp?
leaking pipe or condensation, rising damp is highly unlikely.
Condensation in a heat wave?

yes. I suppose you want an explanation.

Oh yes please, headmaster.

It is temp difference that
causes condensation, not absolute temp (assuming we're talking above
freezing). On a hot day the air can hold a lot of water vapour (the
hotter the air, the more water vapour it can carry). If the hot air has
highish RH, and meets a cold wall on wet ground, the 20C drop can cause
condensation. Although summer condensation is less common than in
winter, it does occur.


I'm perfectly well aware of how condensation occurs thank you, but I've
never seen it during a hot summer, and I doubt you have either.

Every day, when I have a shower.

MBQ