Re: Damp in 9 inch brick wall *LINK* *PIC*

[Anonymous]

No, I'm not a wizard at all. And neither I must be accepted with my experience. All I want to do is giving my thoughts to some questions and problems, I am in contact with since 20 years. OK, may be I'm an expert too. But my expertise will always base on experienced methods, not only hypothesis to sell something to 'moistured' home owners.

What to do against the damp is (I hope) written clearly on the webside. The most important thing is not to do weird actions against the not existing.

So analyze the real source of dampness, then everybody can find the simple way.

And get rid of the fools!



Working against rising damp

 

[Anonymous]

> I nearly got convinced with your improved termination.

Poor Matt

 

[Anonymous]

"But please teach us
- why should the damp take the rising tour under 'your' conditions and will not sink deeper in the ground? "

The last time i passed a Physics exam, it was pretty difficult to get water to move against a pressure gradient.

The water does not want to be in the wall. It want's to get out. Putting wet earth against a dry wall will lead to the wall being damp to at least the height of the earth. I think we can both agree about that.

Ok. If the surface area of the other side of the wall is equal to the surface area of the wall covered with earth the water should not rise, but move straight through the wall and evaporate from the other side. This is not the case in buildings with plastered internal walls. The presence of plaster (or cladding) will reduce the evaporation rate from the internal surface. With the evaporation rate reduced the water inside the wall (still under pressure) will require a larger surface area from which to evaporate.

It can not evaporate from the wall either underground, or through plaster at the same rate as it is moving into the wall and the earth backed against the wall is still exerting pressure on the water. The ONLY way is up.

Partially fill a drinking straw with water (and put your finger over the end). Put a few holes in it just above the level of the water line. Blow through the straw. Not all the water leaves the straw through the holes does it- some rises up the straw past the holes. Pressure differential. Physics in action. Try it.

"- why will the damp not rise (besides the tides) in Hamburg so nearest the much of pressing water (see pic) ? Is there an other, more strong and climby sort of damp in merry old England? "

This is laughable. Cover the river with concrete slabs and the first metre of the wall with render. Now we have comarable conditions to water penetration into a building wall. River water doesn't need to rise into walls to evaprate- surface evaporation works well enough. The pressure over the surface of the river is lower then the river itself-the river loses water to the atmosphere.

You agrue the cause for a understanding of physics, yet you seem to have real trouble with understanding pressure.

Matt Green

 

[Anonymous]

Matt, I also seem to have real trouble with understanding pressure, at least as you've described it. Can you explain again why the water in the wall should rise higher than the earth. What pressure is it under. Your explanation does not seem to be invoking capillary action or movemwnt along vapour pressure gradients and subsequent condensation.

 

[Anonymous]

"Can you explain again why the water in the wall should rise higher than the earth. "

Because it's the shortest possible path to a low pressure environment.

"What pressure is it under. "

The fluid pressure gradient from earth-wall-air

"Your explanation does not seem to be invoking capillary action or movement along vapour pressure gradients and subsequent condensation. "

If capillary action had any effect on water movement in masonry, you would see those effects in the German experiments. You don't, so the effect of capillary action is so small in most cases as to be irrelevant. I say in most cases: what a lot of people don't realise is that the term 'Rising Damp' was originally coined to discribe movement of water through porous stone walls bedded in clay with a high water table. In that situation, you might just get true rising damp. I've never seen it, and obviously the term has been massively over-applied by the remedial industry to great effect. The situation must be very rarely, if ever, correctly identified.

Water moves as a fluid in walls, not a vapour: hence fluid pressure gradiant.

Condensation has nothing to do with penetrating damp rising in walls. Masonry core sampling determines the moisture content from the middle of the wall: condensation is a surface effect. It's pretty easy to tell the two apart as condensation is fresh water and contains no dissolved salts. Ground wayter salts also inhibit mould growth- so the visible appearance is different too.

I shouldn't have started rebutting this. I don't think I've got much to gain. Essentially all I'm doing is allowing Konrad to post yet another link to his site and earn him more money from the advertisments there.

If anyone wants to call me at the office and talk this through, please do.

Matt Green

 

[Anonymous]

Hmmm… If fluids took the shortest possible path to a low pressure environment my beer would be heading for outer space. Fortunately gravity intervenes. I still don’t understand how liquid water can rise above the local water table other than by capillary action.

In a glass tube, water rises to a height given approximately by this formula. Height in cm. = 0.3/diameter of tube in cm. But the characteristics of the materials involved are significant and bricks and mortar are not made of glass with long thin holes. We have seen evidence that capillary action in walls does not wet the wall more than a few cms up.

So Matt, I don’t understand your comment “Water moves as a fluid in walls, not a vapour…” Why can’t water move as a vapour? Walls have interconnecting pore spaces – they are ‘breathable’- so vapour should move through and up the wall along any vapour pressure gradient. Just above the base of the wall where it saturated by a high water table and what limited capillary action has happened the relative humidity may be 100%. High up in the wall, in areas from which evaporation can occur, the humidity will be lower. Water vapour will move, upwards. If the vapour encounters a local dew point condensation will occur. Adsorption by hygroscopic minerals may occur even above the local dew point. Timber will also absorb water from vapour at air at below 100% humidity.

 

[Anonymous]

Oh Matt, this thread seems to increase to a really professional scientific discussion between water lovers - and I'm such a stupid greenhorn concerning english pressing water and water pressing!

Please accept that my scientif english is quite pidgin although this forum is filled over with so highly culturated and well establihed native speakers, poetry lovers and so on. I feel a little bit foolish and hesitate to presentate my poor thoughts and meanings in english. But in spite my doubts I will try it once again - my contribute to common interest to thsi topic which I supposed in UK too.

What you are saying about the behaviour of english pressing water and water pressing is really astonishing for me. Never had I thougt, that render - for instance lime render - can moisture up walls in such cases. I supposed onto now, the bigger surface of the porous lime render will help to dry out moistured walls, and this is my experience here.

Besides I have never found rising damp (or better damp rising?) in spite of absolutely water-proofed inside layers on the wall.

German water prefers to sink into the ground, also if it is in the wall and the foundation base wall has a perfect (against rising damp senseless, you know my opinion) damp-proof course. The rules of gravitation will force german water into the ground and if it can not go there and the wall is filled up onto the ground level, it will prefer to go besides the wall in the garden, because german foundations and walls mostly have more resistance to water pressure than the typical german meadow and soil.

And if there is a so high water pressure in the german soil, maybe it will create an artesic fountain spraying out and water the garden or it will decide to fill up a new lake or a little brook and search the next river before it decides to do such strange things in our walls.

Even rain of the damaged gutter dropping in the wall will find the way to the german soil some time after filling up a both side water-proofed wall, plastered with most disgusting plastified layers.

When german water comes in walls under pressure from the nearby damp soil, it will stay there quite willingy up to the time when it is forced to come out by rigid means like effective heaters in the water-filled pore system. Which not often happens, as I suppose. Besides there is a natural damp degree in our walls, remaining until the last days, I suppose. What I want to say is that the german water will refuse rising in all cases in german walls.

So it is from Kiel to the Alps and from Rhine to Oder, at least what I know. Exiting to hear about the strange water in England, really! And many thanks for the astonishing water lecture, i'm really willing to learn more about it.

Sorry for the long thread.

 

[Anonymous]

Im afraid Im loosing the will to live and feel its time to move on.

Bye Bye.

PC

 

[Anonymous]

Live and let dry!

Good luck!

Konrad