Rising Damp - A Myth?

[Man at B&Q]

No, you want the evaporation to mimic real world conditions. How many walls have hard plastic shells?

MBQ

[Man at B&Q]

All of which are easily cured and do not require "treatment".

MBQ

[polygonum]

That was what I meant, really. The outer surface evaporation rather than from the top of the pipe/column.

[Man at B&Q]

Which is easily diagnosed and fixed without "treatment".

SWMBOs g-father used to fit slate damp courses a few feet at a time. I'll leave it to the reader to figure out why they didn't do the whole house in a day.

MBQ

[Man at B&Q]

So they actually knew what they were doing!

The customer needed an expensive cure to believe in.

MBQ

[Steve Firth]

Because they didn't own a diamond chainsaw?

I saw one of those being used to fit a physical DPC to a cottage in Surrey. The chainsaw had crawler tracks. One man drove it around the outside of the house another followed inserting the DPC by hand. They also worked a few feet at a time but it took less than a day.

[stuart noble]

As a starting point I'm more interested in how far the damp can rise in ideal conditions, and in an ideal medium. What would be the ultimate capillary type material? If we say 4 sand to 1 chalk is roughly what old lime mortar walls consist of, then dry sand alone might be a good enough guide. But how to explain why the sand on a beach is dry quite close to the water's edge.

[Peter Parry]

Oh yes, in more ways than one :-) Quite a few people actually felt a bit sorry for them. They had been around for some time and were known for doing very tidy work. When TS investigated they were, I gather, quite surprised that they couldn't find a single dissatisfied client

In nearly all cases the damp was of course caused by the soil and shrubs on the outside walls, clear those away, lower the soil level a bit and the vast majority of penetrating problems go away by themselves. The chemical damp proofing bit is rarely needed.

The customers of course did think they were buying a chemical DPC (and were charged for one), not just a days work by labourers clearing abound the house but all they needed to buy was the days work.

[harry]

[Big Les Wade]

The sun, via evaporation.

[harry]

So how can the water be "sucked up" more the 30 feet? (The max for absolute vacuum)

[polygonum]

Sorry - are you saying that more sun is required to evaporate a single water molecule from the top of a tall tree than from a blade of grass?

(Obviously, controlling other parameters such as atmospheric pressure, temperature, humidity.)

[Andy Champ]

Surface tension. Roughly.

The Wiki article makes some sense.

Andy

[Grimly Curmudgeon]

He's full of shit, as usual.

[usenet2012]

In message , Mark writes

And a headline and a paragraph.

"Rising damp is a myth, says former RICS chief

26 June, 2009 | By Richard Waite

Stephen Boniface, former chairman of the construction arm of the Royal Institution of Chartered Surveyors (RICS), has told the institute?s

40,000 members that ?true rising damp? is a myth and chemically injected damp-proof courses (DPC) are ?a complete waste of money?."

[Big Les Wade]

You're right. Transpiration doesn't draw water up the trunk. The truth is that every tree has a little angel hidden in the roots, equipped with a stirrup pump with which he constantly pumps water up the stem. Every now and then God feeds the angel a special communion wafer packed with angel-energy to keep him going.

Conservation of energy is maintained because, every time God issues a new wafer, he slightly reduces the value of k in the equation relating the energy tensor of matter to the Ricci tensor.

[The Natural Philosopher]

capillary action.

[Big Les Wade]

I don't think I commented on that, I just said that transpiration works largely by evaporation. Some other mechanisms help as well, such as root pressure and capillary action.

[harry]

There is a (poor) explanation here.