SPLIT: Rising damp?

[TheLastMan]

I am a surveyor, but not a building surveyor so I am not qualified to diagnose damp problems in residential property. I do, however, look at commercial properties all the time in the course of my job as a valuer and have therefore seen a lot of dodgy damp walls.

My take on this is that rising damp can exist, but rarely (if ever) starts on its own and is usually caused be the wall becoming damp through another cause first.

I am intrigued by the picture of a brick column standing in water and the damp not rising above the first course. In a perfectly dry atmosphere using "soft" water that is a plausible experiment. However this kind of situation rarely exists in real life.

In most parts of the UK exposed external brick walls are subject to driving rain or overflowing gutters often soaking the wall from top to bottom. So a better version of the experiment for UK building condtions would be as follows:

Build the brick column with soft absorbant UK style external bricks and usual sand and cement mortar. Stand it in a tray filled with "hard" London ground water laden with disolved calcium, magnesium and sodium carbonates. Spray the column with water continuously for about 2-3 hours until it is soaked through - both mortar and bricks - to mimic the effect of driving rain or over-flowing gutter.

See how quickly the wall dries out.

Repeat the experiment but this time with a DPC installed between the lower course and the rest of the column and see if it dries out any quicker.

Ideally repeat the water spraying weekly or so for a few years and see if the columns dry out more quickly or slowly over time.

Now I haven't tried this experiment myself, but I am pretty certain I know what will happen. I would be interested to know if anyone has tried this in real life.

Water will not spontaneously create a continuous capillary column through alternating brick and mortar courses however if the brick column is already wet, then capillary action may be enough to sustain an existing capillary column through the different materials - rather in the same way that a siphon needs "charging" before it will work.

After a while the brick column will become laden with hygroscopic lime salts and will then be able to quickly absorb water from the tray and form a capillary column. Even if it doesn't there is bound to be another shower of rain soon to recreate the original problem.

I may be wrong of course, but if anyone cares to do the experiment I would be intrigued to see the result.

I have seen rising damp solved through the installation of a chemical damp-proof course. I have also seen many pointless installations of chemical damp proof courses where the real problem was a perfectly good DPC that has been bridged by earth, badly installed concrete floors and patios, badly applied external render etc.

This is not a "black and white" argument. Rising damp can exist but usually where there are sources of damp other than ground water and in areas with a lot of dissolved salts in the groundwater.
_______________________________
Lynda, moderator

please do not hi-jack posts.

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This post has now been split

 

[AndersonC]

Interesting post there Lastman.

I would like to pick up on the point where you say you have seen rising damp solved by chemical injection. How many times have you seen this and in all cases was the internal plasterwork replaced to a height of 1 metre? Was the conclusion that the RD had been solved reached by using a damp meter on this new plaster or on bare brick? What range of timescales have existed between injection of the chemicals and you confirming the absence of RD?

The reason I ask is that the possibility exists that you may well have been simply measuring the damp levels of new, dried out render/plaster after the chemical injeciton had been carried out (unless you'd left it for a few years prior to going back and measuring the damp levels).

This factor, in turn, doesn't categorically conclude that chemical injections solve damp, moreso that by removing damp plaster and replacing it with new, that you record different damp levels in two (potentially very) different conditions of plaster.

 

[TheLastMan]

Interesting post there Lastman.

I would like to pick up on the point where you say you have seen rising damp solved by chemical injection. How many times have you seen this and in all cases was the internal plasterwork replaced to a height of 1 metre? Was the conclusion that the RD had been solved reached by using a damp meter on this new plaster or on bare brick? What range of timescales have existed between injection of the chemicals and you confirming the absence of RD?

The reason I ask is that the possibility exists that you may well have been simply measuring the damp levels of new, dried out render/plaster after the chemical injeciton had been carried out (unless you'd left it for a few years prior to going back and measuring the damp levels).

This factor, in turn, doesn't categorically conclude that chemical injections solve damp, moreso that by removing damp plaster and replacing it with new, that you record different damp levels in two (potentially very) different conditions of plaster.

Not being a building surveyor I do not routinely carry around a damp meter. My observations are based on visual observations and the comments of tenants.

I cannot recall exactly the number of times I have seen this (been working for 30 years now). My observations are of properties I value periodically - usually annually. I reckon we are talking in the low teens in terms of numbers. The problem has typically been in an old 18th/19th Century terraced shop or office building (often converted houses) and has manifested itself on a solid brick rear wall or side alley (end terrace). The front walls are usually glass! These types of building were sometimes badly / cheaply built and omitted any kind of DPC.

My observations usually follow the following pattern.
Turn up at property and notice large, dark, external damp patch on lower section of bare brick external wall - often with obvious tide marks of salts efflorescence where the damp has reached its maximum extent.

Check for any evidence of DPC bridging. About half the time there is. In which case I suggest tenant sorts it out. These are usually external ground levels built up to cover DPC. Subsequent inspections usually show the problem cured.

It is worth pointing out at this point that bridging a DPC can cause damp to rise up the wall where it is bridged - any surveyor will tell you this. In my experience it is the main cause of rising damp in older buildings.

Where there is no DPC and no other obvious source of damp I suggest tenant gets a "proper" surveyor round to do a more thorough investigation (lifting floorboards etc).

This rarely finds anything new and the source is clearly water rising up the wall by capillary action from damp ground. Sometimes poor external drainage can lead to puddles forming against the wall which exacerbates the problem - rather like the stack of bricks in a tray of water. Often these walls have old lime plaster mortar rather than sand/cement which may make the problem worse as this kind of mortar is hygroscopic and actually absorbs water more readily than the bricks it is bedding.

Where appropriate the tenant may get a chemical DPC installed. A year or so later I will reinspect the property for the valuation and where the DPC has been installed the obvious external damp patch has gone.

As you say, installing one of these DPCs usually involves replacing damaged internal plaster with new waterproof plaster. I make very sure that this starts well above the level of the DPC as internal plaster itself can cause bridging of the DPC.

In one case the wall was so wet I recommended the tenant hack of the plaster up to 2m internally and leave the wall bare to give it a chance to dry out. Which it did. The problem did not return after he replaced the plaster.

It is very difficult to be definitive about these things but over the last 30 years I have come across plenty of cases of obvious rising damp - either because there is no DPC but more usually because it has been bridged by a build up of soil / tarmac / paving that has raised the external ground level above the DPC.

Tell any experienced UK building surveyor that "there is no such thing as rising damp" and he will probably collapse from laughter. The fact that it is very often incorrectly diagnosed and even more frequently badly repaired does not mean it does not exist. It is most frequent in the following conditions - which are particularly prevalent in the UK in Victorian buildings and probably not so common elsewhere in Europe where different construction methods are used.

1. Soft clay bricks
2. Thin (1 brick length thick) solid walls
3. Lime mortar
4. Persistently wet ground (clay sub-soil) or poor drainage
5. Driving rain soaking the wall
6. Missing DPC
7. High level of 'lime' salts in groundwater (chalky sub-soil).

Rising damp is usually prevented if even one of the above conditions are modified as follows:
1. Harder 'engineering ' bricks
2. Thicker solid wall or cavity wall less prone to getting soaked by rain
3. Sand / cement mortar
4. Good external drainage taking rainwater away from footings
5. Waterproof external rendering (above DPC of course!)
6. DPC (slate, engineering bricks, mastic, PVC sheet etc)
7. Soft ground water area (granite or sandy sub-soil)

 

[anobium]

Why has this topic suddenly reappeared.
It 's not by any chance related to my comment about Softus under another post headed,

Is This Damp? If So, What Kind?

I thought that we had said all there was to say on this matter, until that is Softus came out with his recent remark.

 

[TheLastMan]

Why has this topic suddenly reappeared.

My fault entirely. Another recent post pointed to the old thread on rising damp and after reading it I felt compelled to comment after reading a lot of half baked conspiracy theories there.

Don't worry, I have now said all I want to on the subject

 

[anobium]

This post is in response to a post from Softus which for some inexplicable reason has been deleted, in which he accused me of goading him and highjacking a subject, and telling me that I should start a new topic.That is the basic gist of it as I recall it anyway.
Unfortunately I had to go out and have now only got round to responding.
Firstly my post was on the subject of rising damp but with regard to comments made by Softus on the subject.
His comments were as follows;
Softus wrote

On the inner skin, or on a solid wall, the purpose of the DPC is to connect with the DPM (if there is one) to form a contiguous barrier to moisture that would otherwise be able to creep up the join between internal wall and internal floor.

I responded to this comment by saying that at long last, Softus finally accepts that there is such a thing as rising damp, albeit he gave it another title , creeping damp.
I have to admit though, that, I was looking for some sort of response from him, along the lines of grovel grovel etc.
I can dream can't I!
As for goading Softus, people and glass houses springs to mind.
I hope that this clarifies the matter, which has not been helped by the removal of various posts on the subject by others who are nameless.
Waffle complete, over and out.

 

[Softus]

I'm coming to the conclusion that you're a bit of a sneaky character, anobium. You seem incapable of sticking to the point within one topic, and, rather than ask me directly what I mean, or to confirm an interpretation that you've made, you seem to prefer speaking to the gallery in a taunting fashion.

So, for the record, I'll respond here to your points, irrespective of whether or not they arose on another topic.

This post is in response to a post from Softus which for some inexplicable reason has been deleted, in which he accused me of goading him and highjacking a subject, and telling me that I should start a new topic.

You were goading me, and you did introduce something from another topic that I still can't remember anything about, and to which you've still not posted any Hyperlink.

Firstly my post was on the subject of rising damp but with regard to comments made by Softus on the subject.
His comments were as follows;
Softus wrote

On the inner skin, or on a solid wall, the purpose of the DPC is to connect with the DPM (if there is one) to form a contiguous barrier to moisture that would otherwise be able to creep up the join between internal wall and internal floor.

I responded to this comment by saying that at long last, Softus finally accepts that there is such a thing as rising damp, albeit he gave it another title , creeping damp.

There is no such final acceptance on my part, but nor is there denial. If you would care to read the very post on this topic, you'll see that I have said that the claim it doesn't exist is deliberately provocative.

All along, repeatedly, I've been asking anyone to tell me of an occurrence of rising damp. Only three people appear to be able to comprehend this request - one being AndersonC, the second being TheLastMan, and the third being a very pleasant German gentleman whose name I don't have the time to look up at the moment.

I have to admit though, that, I was looking for some sort of response from him, along the lines of grovel grovel etc.

Why? Is that the way you conduct a reasoned and rational debate? With grovelling from one or other party?

If you don't understand what I've written in response to you, then please ask me to explain it. Your preferred alternative (of inferring within it some admission that doesn't exist) is getting none of us anywhere.

As for goading Softus, people and glass houses springs to mind.

So - you justify your behaviour on mine then, do you? If I make a mistake, or an error of judgement, or do something humanly fallible, then it excuses you from doing exactly the same thing, even if you know better? That's just f***ing childish.

I hope that this clarifies the matter, which has not been helped by the removal of various posts on the subject by others who are nameless.

Why be so vague? It's obvious that a moderator has deleted a post, and without any trace of a reason. I don't know why they did this any more than you do, but it wasn't necessary and it wasn't helpful.
__________

If you want to know if I still think RD doesn't exist, then the answer is that I think it doesn't. There is plenty of food for thought in the posts of this week, with points being raised that hadn't been before. However, it remains incredible to me that, of all the members of the forum who are prepared, directly or indirectly, to tell me that I'm wrong, that only one person has ever claimed, unequivocably, to have first-hand knowledge of an address in this country where a RD problem existed and has been cured by introducing, or reinstating, a damp proof course, with no other remedial work carried out.

Does that not strike anyone else as rather odd?

 

[anobium]

Softus wrote

I'm coming to the conclusion that you're a bit of a sneaky character, anobium. You seem incapable of sticking to the point within one topic, and, rather than ask me directly what I mean, or to confirm an interpretation that you've made, you seem to prefer speaking to the gallery in a taunting fashion

Check the facts, I have only ever posted comments related to rising damp on this thread.
As for my character you are entitled to your opinion
Softus wrote

You were goading me, and you did introduce something from another topic that I still can't remember anything about, and to which you've still not posted any Hyperlink.

Wasn't, Oh go on then, I've already admitted that I was trying to get a response from you.
But what other topic did I introduce, please clarify
Softus wrote

There is no such final acceptance on my part, but nor is there denial. If you would care to read the very post on this topic, you'll see that I have said that the claim it doesn't exist is deliberately provocative.

All along, repeatedly, I've been asking anyone to tell me of an occurrence of rising damp. Only three people appear to be able to comprehend this request - one being AndersonC, the second being TheLastMan, and the third being a very pleasant German gentleman whose name I don't have the time to look up at the moment.

This is where you lose me.
You say there is no acceptance or denial and then you refer to 3 people who have given you the answer which you asked for originally.

Softus wrote

Why? Is that the way you conduct a reasoned and rational debate? With grovelling from one or other party?

It was meant to be humorous.

Softus wrote

So - you justify your behaviour on mine then, do you? If I make a mistake, or an error of judgement, or do something humanly fallible, then it excuses you from doing exactly the same thing, even if you know better? That's just f***ing childish.

Thats a rather childish response on your part.

Softus wrote

Why be so vague? It's obvious that a moderator has deleted a post, and without any trace of a reason. I don't know why they did this any more than you do, but it wasn't necessary and it wasn't helpful.
__________

I know it was a moderator but I didn't know his or her name, but I agree that it wasn't helpful
Softus wrote

If you want to know if I still think RD doesn't exist, then the answer is that I think it doesn't. There is plenty of food for thought in the posts of this week, with points being raised that hadn't been before. However, it remains incredible to me that, of all the members of the forum who are prepared, directly or indirectly, to tell me that I'm wrong, that only one person has ever claimed, unequivocably, to have first-hand knowledge of an address in this country where a RD problem existed and has been cured by introducing, or reinstating, a damp proof course, with no other remedial work carried out.

But this is precisely why I raised the question about your remarks in the first place.
How can you on one hand say that you don't think that rising damp exists and then tell somebody on this forum that the purpose of a dpc at the wall junction where it meets the damp proof membrane is to prevent moisture creeping up the wall.?
Have a nice day mate.

 

[Softus]

How can you on one hand say that you don't think that rising damp exists and then tell somebody on this forum that the purpose of a dpc at the wall junction where it meets the damp proof membrane is to prevent moisture creeping up the wall?

If you don't already understand how, then it's likely that you never will.

 

[Bedge]

Surely experiments are relatively easy to do regarding Chemical DPC and rising damp (and any other product for that matter). You could Chemical DPC one wall and not another in the same environment and then monitor the effectiveness? Has no one done this?The manufacturers? The product would have had strict testing, especially where where are mortages depending on these surveys and where legalities are concerned. To say rising damp doesnt exist seems ridiculous to me. It seems to me that misdiagnosis, bandwagon, cowboy are words that could be regularly used in the same sentence when discussing the issues behind the cause, diagnosis and solution to damp. Its wide ranging as it is complicated. Why is there no regulating body? Who is responsible for damp proofing gone wrong when the traders gone bust. These issues need to be addressed so that we can move the wheat from the chafe. What a rip off industry. Every "expert" has a differnet bloody opinion. Its like betting on the dogs.