Potential damp problem ... or not ??

[JasonHardy]

Hello all, we live in a 1940's detached solid brick wall house. When we bought it, the survey picked up on damp along the outside wall, furthest from heat source (radiators). There were no visible signs - no wallpaper blistering, no signs of plaster damage. We had a guy round to give a second opinion - he stuck his meter in the wall and confirmed that there was damp.
This was 18 months ago. Over the winter we did get some mould on that wall at skirting level, which i put down to condensation and washed off with bleach. Still no signs of any damage to paper/paint or plaster though.
We've just had someone round to quote for internal thermal boarding along this outside wall, who also with his meter has diagnosed damp and suggested chemical treatment.
I'm still sceptical as to whether we actually have a problem - it just seems odd that there are no physical signs.
There is nothing piled up against the outside wall, or leaking guttering.
Is this a case of a gravy train for damp proof trestment companies, or could we have a genuine problem ?
Any advice would be very much appreciated,
Thanks

 

[Bilioustrumpstaine]

The fact that the problem became more apparent in the winter lends itself to the problem being condensation rather than rising damp. The wall being furthest from the heat source will be the coldest and therefore where condensation will strike.

Lets face it we get as much rain in the summer now as in the winter.

A lot of these damp "specialists" are just looking for work. If you want an unbiased opinion then you will need to engage a qualified surveyor who will conduct an investigation for you. These companies that offer "free" surveys are in fact offering free quotes for work which in a lot of cases is not required.

Is there an option of getting some heat at the far end of the room affected. Do you have plenty of ventilation.

 

[^woody^]

How can someone diagnose damp without actually diagnosing the cause of damp? Thats not a diagnosis it's just a statement

So what damp is it? Rising, penetrating, condensation or a combination?

You need to determine the cause before you can decide on the appropriate remedy.

The wall needs to be investigated in terms of condition, orientation, and construction. Then each of the possibilities can be discounted, to narrow it down to the most likely cause of any dampness, and then appropriate tests made to confirm this

Then you can work on the solution

 

[JasonHardy]

thanks very much for your replies, so far, kind of confirms my suspicions

 

[nam]

Hello all, we live in a 1940's detached solid brick wall house. When we bought it, the survey picked up on damp along the outside wall, furthest from heat source (radiators). There were no visible signs - no wallpaper blistering, no signs of plaster damage. We had a guy round to give a second opinion - he stuck his meter in the wall and confirmed that there was damp.
This was 18 months ago. Over the winter we did get some mould on that wall at skirting level, which i put down to condensation and washed off with bleach. Still no signs of any damage to paper/paint or plaster though.
We've just had someone round to quote for internal thermal boarding along this outside wall, who also with his meter has diagnosed damp and suggested chemical treatment.
I'm still sceptical as to whether we actually have a problem - it just seems odd that there are no physical signs.
There is nothing piled up against the outside wall, or leaking guttering.
Is this a case of a gravy train for damp proof trestment companies, or could we have a genuine problem ?
Any advice would be very much appreciated,
Thanks

So basically you had 3 independent people tell you there is damp in the exact spot and you done beleive them? The mould that was on the skirting board could be classed as physical sign. you dont have to have anything piled up next to the wall, if the dpc is crack water can seep up. chemical treatment shouldnt be very expensive. There is a damp proofing paint (I bought a tin to do one of my property but cant remember the name of it) it cost about £20 for a 4 litre tin but if you are going to have the wall insulated I would get it professionally treated first

 

[nam]

How can someone diagnose damp without actually diagnosing the cause of damp? Thats not a diagnosis it's just a statement

So what damp is it? Rising, penetrating, condensation or a combination?

You need to determine the cause before you can decide on the appropriate remedy.

The wall needs to be investigated in terms of condition, orientation, and construction. Then each of the possibilities can be discounted, to narrow it down to the most likely cause of any dampness, and then appropriate tests made to confirm this

Then you can work on the solution

Easily, just test the wall with a damp meter or a multimeter set to ohms setting.

 

[foxhole]

There are no meters capable of detecting damp in a wall, none penetrate deep enough to give meaningfull readings.[the best on go to 25-30mm].
Correct assessment has to be by drilling and taking a core sample.Meters only detect surface moisture which is usually down to condensation.

 

[Symptoms]

I have a 25+ year old Protimeter that's got deep wall probes (getting on 6" long); these have fly-leads that plug into the unit. Hardly ever use this tackle now (it's quite a large analogue instrument and too bulky to hump around) - I use one of their Mini jobbies now and you can get long probes for these although I never bothered to get them with it.

These instruments can only ever give an indication of moisture of some kind and should only be used to guide further investigation and not relied on to provide a difinitive answer ... something that should be remembered when getting-in the so-called damp companies (they want your money).

 

[JasonHardy]

thanks all again, your comments are much appreciated.

it's not that i dispute the fact that there is moisture present (there must be if 3 independent companies have detected it .. as mentioned in one of the replies).

i just have my doubts that it's structural damp, and not just surface moisture due to condensation - the wall is obviously the coldest part of the room, and also north facing. If i worked for a damp company, i'd certainly make a bee line for it if i wanted to obtain a positive reading.

 

[^woody^]

Easily, just test the wall with a damp meter or a multimeter set to ohms setting.

LOL - which damp company do you work for?

Let me guess .... one of the ones which put a meter on the wall, let it light up and then proclaim "Oh yes, you've got damp here".

The trick is determining what is causing the dampness, and that is where you will fall down, judging by comments like that

 

[alittlerespect]

The problem you describe is fairly typical for the type of construction, and is caused (as you rightly say) by condensation, or to be more precise a mixture of surface condensation and interstitial condensation. The condensation problem occurs because warm air (which holds more moisture than cold air) meets a cold surface (surface condensation) and then going into a bit more depth interstitial condensation forms where the warm (internal) part of the structural element (wall) meets the cold (external) structural element, the warmer element will cool down and vapour entrapped in the structural element will reach saturation point and moisture will be deposited (interstitially) within the structural element.

Installing wall insulation would overcome the problem, however, you must ensure that a vapour barrier is included in the design. The whole purpose of the vapour barrier it to stop the warm moisture laden air(vapour)coming into contact or permeating into the wall.

Spec wise a 50mm 'thermaline super' urethane insulating board (british gypsum or similar approved) would significantly reduce heat losses, urethane is also vapour resistant which gets over the problem of introducing a vapour control layer. As a note, the insulating board should not be fixed directly to the wall, normal practice is to use 'plaster/adhesive' dabs which provide a small cavity which effectively isolates the cold external wall from the insulation.

Regards