Types of Damp Proof Course

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Re: Types of Damp Proof Course

Post by Evelyn » Fri 17th Mar, 2006 4:22 pm

I add to what I posted above - yes, walls had certainly been damp, and that's why the bitumen/silver foil paper had been put there.

The fact that there was at least two foot of wall under the outside path, and the exterior pointing on a wall which receives a great deal of weather was very defective may have explained some of it...

Other causes - blocked ventilation, plastic sheet laid on top of flagstones, etc, were never mentioned either. It was all 'rising'...

This was a 'reputable' national firm...

I think you cannot extrapolate anything very meaningful from those Cardiff results without knowing a great deal more - and the solution (sorry about the pun) may have been something less destructive and expensive than chemical injection of course.

Matt - I have a pic I have taken of a large stone from one of our outbuildings, drilled in four places to inject - looks bloody awful, and I'm not terribly convinced it had any effect at all on 'rising damp'.

Maybe the lack of pointing would have contributed to any perceived problem

As with the holes drilled and injected into the interior wall of our pantry, a foot or two below the exterior ground level in a rubble stone wall.

I think there may have been a better and cheaper solution, which also involved less destruction.


Re: Types of Damp Proof Course

Post by GRC » Sat 18th Mar, 2006 9:43 am

High ground levels ain't rising damp - lateral penetration. Funny, seems to leave less salts behind than 'traditional' rd where water is *rising* up through a wall by capillarity.

Sorry, mate, but BRE are pretty competent at what they do, especailly Trotman, Saunders and Sharp - their Cardiff work was traditional rd; yes and it was active.

I was going to go through my last 25 years + of lab data but it would take too long.

Most evaporation takes place from surfaces - hence all things being equal (as they are usually not of course) water will rise higher in thick walls than thinner ones - all boils down to surface to volume ratio.

The salts do have some other effects other than moisture absorption - got some nice 'gold' wallpaper that turned green (no pun intended) when applied over a contamianted finish - the 'gold' is derived from copper salts.

In domestic buildings over nearly 30 years I have only investigated 1 that was misdiagnosed - every one where there was a dispute over damp-proofing works rd was the base problem.

If the diagnosis of rd was that bad, ie, badly misdiagnosed, then treatment for such would be a waste of time and the dampness would continue - this does not appear to be the case.

The real question, however, is does it need attention? Severe rising damp is NOT common and where it is don't bother to rely on injection - it is highly unlikley to work in those dituations! Injection works well on dry walls though - never seen one fail yet - but does that sound too cynical?

In a nutshell that is the result of nearly 30 years of lab data - don't know if you have any to add, but as ever it would be interesting


Re: Types of Damp Proof Course

Post by GRC » Sat 18th Mar, 2006 9:47 am

Hi E,

You can get the *full* investigation from BRE - it is in the public domain - the work was undertaken by scientist and engineers.

AS stated to Matt they have spent many years investigating dampness in buildings - they are not fools and readily know the variables.

The Damp Man

Re: Types of Damp Proof Course

Post by The Damp Man » Sun 19th Mar, 2006 4:55 pm


Can you please provide details of your experience
in the investigation of rising damp. Are you saying that BRE got it wrong, I dont think so.

Wake up women and accept that Rising Damp does exist and not everthing is due to high ground levels and drainage problems.



Re: Types of Damp Proof Course

Post by Evelyn » Sun 19th Mar, 2006 5:50 pm

I'm not saying anything at all - but I am aware of the limitations of any sort of research findings. As is Matt I'm sure.

Konrad now - he was equally as convinced damp didn't rise I recall.

I'm also concerned that far too much expensive and damaging intervention of the wrong sort happens because of 'rising damp' diagnosese.

It does make some people a living I appreciate.

Evelyn (very, very dry).


Re: Types of Damp Proof Course

Post by GRC » Mon 20th Mar, 2006 12:08 pm

Hi E,

There is a heck of a lot of data from BRE over the last 50+ years, and also a lot from the Australians and Italians. Much of this is not research data but field data. I think it is reasonable to accept that those involved in the above are not idiots, but are thinking scientists, engineers and building professionals. It is also very difficult to create rd in the lab - one just cannot re-create aged, old mortars.

My own field data other than from samples sent in indicates that RD is not uncommon BUT severe RD is, ie, where it is causing visible dampness/spoiling! (we are, of course, talking about older properties) Take a nice piece of Victorian lime mortar and stick it partially in water and see what happens.

Why RD occurs in some properties and not in others is still a bit of a mystery. For example, this house has 'dry' bickwork below the physical, but one just down the road is absolutely sopping below the physical dpc.

A friend of mine in the village owns the old forge (1700's?) - we drilled and sampled his walls and he had 'classic' rd with one heck of a salt problem to go with it - and there was a distinct visible problem.

Interesting though.



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