Rising Damp - A Myth?

[The Medway Handyman]

Watching a re run of QI the other night & Mr Fry stated that rising damp was a myth - it didn't exist.

Comments?

[Brian Gaff]

Well where does it come from then?

Brian

[sm_jamieson]

I thought he said that but I was only half listening. Tests of newly built brick walls seem to agree that rising damp is quite unlikely. However, I suspect old porous bricks or old mortar can wick moisture up a wall to some extent due to capillary action, but probably to a much lesser extent than blotting paper. Also, once a wall is already damp it might be more likely to continue. A bit like previously damp walls attracting more damp due to hygroscopic salts. And these two issue could interact. For some reason rising damp seems to attract religious argument, much like human-attributed global warming ... Simon.

[jgharston]

Where I've found internal damp on walls I've usually found that it's the plaster that has been sucking the water up via capillary action. Cleaning all the plaster off has usually resulted in a dry wall. My best repair consisted of plastic tanking bonded to the brickwork and tucked through the floorboards into the cellar, 1/4" battens screwed through the tanking into the brickwork and two sheets of bathroom grade plasterboard board-screwed to the battens and skimmed. Your milage may vary.

JGH

[Dave Plowman (News)]

It's certainly *far* less common than damp proof course installers would have you believe.

[Tim Streater]

Last house we owned *had* to be kept damp - walls made of claybat.

[harry]

A lot of money been wasted on DPC/DPMs in that event. The man is a complete tosser. A few minutes with a damp meter can show rising damp in a suitable place.

[harry]

That's probably true.

[The Medway Handyman]

[Nightjar]

That was the conclusion the Building Research Establishment came to, possibly in the 1970s, when they stood various forms of wall in tanks of water for months on end. It was reported in the newspapers at the time, but didn't seem to make much impact on most people.

Colin Bignell

[John Rumm]

Yup, its not mythical, but its certainly far less frequently seen in the wild than they would have you believe.

The BRE did research on it that included building multiple piers of brick in a tank of water and seeing how far water would rise up each. IIRC, they found that you could get some rise with very soft bricks, lime / sandy mortar etc.

(BRE Digest 245 is often mentioned)

BS6576:2005 gives a diagnosis procedure - perhaps a summary of it in the wiki might be useful?

[Peter Parry]

Correct.

It can also show the most likely nesting places of con artists. A few minutes with a "damp meter" will show anything the operator wants. What it can't do is detect rising damp.

[stuart noble]

I have tried without success to get moisture to rise significantly by capillary action in a whole load of different media, mostly connected with gardening. They say it can rise up to a metre, in which case a low hanging basket might water itself. Fat chance!

[Nightjar]

My recollection is that, even in the worst cases, it only rose an inch or two - well short of where a DPC would be.

Colin Bignell

[John Rumm]

True

Which man?

I am not aware of any damp meters that can tell you the cause of the damp.

Analysis of the salts contained in the damp material is usually the only way to identify whether the water is ground sourced.

[charles]

that depends on how high the water table is. In times of exceptionally heavy rain, the water outside is only 1 brick below the damp course.

[Nightjar]

Bricks are 3" high. Where's the problem, even if you had very soft bricks, rather than commons?

Colin Bignell

[polygonum]

Just wondering if fluorescein (or another dye) might work in this context? Pour a bit into or around the suspected source, wait, shine UV.

[Kenny]

More Fry Bollocks, from the font of all knowledge. He's great with his sound bytes, but the content is often lacking.

I thought posters here read the Reg ?

[The Natural Philosopher]

he is as usual talking bollocks

Its not as comon as its supposed to be but it surely exists.