penetrating damp


  #1  
Old 11-07-01, 02:11 AM
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Hi

I'm from the UK so I apologise if any of the terminology I use is wrong to the rest of the world!

I've recently bought a detached house. It was built in 1880 as an industrial workshop but eight years ago it was converted into a home. A damp proof course was applied.

The house is on two stories with the bedrooms downstairs and the living areas upstairs. It's built out of local stone (it's in Derbyshire, for those who know the UK, so we're talking a fairly wet and windy place).

In one of the bedrooms there's a damp in the corner. This corner gets little light and little ventilation. The damp extends from the corner down one wall around two/three metres, and around a metre on the other wall. It's roughly triangular from the corner downwards (like a tent in shape), with the highest point in the corner of the damp appearing to be around a metre/one and a half metres high.

I suspect it's simply condensation -- the brick walls are around 20cm thick and get cold at night -- but a 'specialist' from a damp proofing company reckons it's penetrating damp. I ought to point out that the house is on a hill and the left hand side of the house is effectively starts a metre underground, with the right hand side being 'above ground', as it were.

What I'd like to ask the forum is if anybody knows any tell tale signs of various kinds of damp - condensation, penetrating, and rising. For example, we're told that if it is condensation then behind the skirting board shouldn't be damp free, but there's damp there (in fact, it's very damp, as it happens, much more so that any of the plaster).

We've knocked some of the surface plaster off but the render (ie plaster applied to the bricks) is staying put - surely if it were penetrating damp then this would be falling off too?

Any help would be appreciated.


 
  #2  
Old 11-07-01, 08:12 PM
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Not to worry, English is fluid. We have a hundred or so dialects in the USA alone. Ebonics, (Oakland, California), almost became an officially recognized dialect. "Yo, les' kick-it". And, sofa, couch, davenport, and chesterfield, are one in the same. Ifn' u cypher strange... do it rea-l slow, cousin.

Test for condensation: hang a mirror against the wall or seal clear plastic to the surface with tape then wait. Moisture on the exterior surface of the plastic or mirror is condensation.

I really "love" damp definitions! Someone, [salesman, no doubt], strained to make simple appear more complex than it is. I especially love horizontal and lateral penetrating damp, and falling damp. [Rising damp is the only one that lingers in the U.S.}.

Rising Damp: water is drawn from the ground up through the base course of masonry work by capillary action. [Normal soil percolation, inadequate drainage, failed damp course, rising ground water table or an underground spring that has changed course]. [If either of the latter two apply, you have a real problem].

Telltale signs: wet ground at or below the foundation, delaminated "render" or plaster and crystallized surface salts, wet and dry rot, mold and fungus. Apparent wet spots or salts rising on the surface from the base course. Remember, a damp course does not divert existing subsurface water. The same water may form as condensation instead, if it's not dealt with.

Penetrating Damp (subs horizontal and lateral): collectively water penetrates through exterior masonry work from the atmosphere or from a ground source at any course level. Typically "horizontal" means rain, heavy due or fog, sleet, or snow, and lateral means sideways from a ground source at any masonry course level.

Masonry is porous. It is not vapor proof. Vapor barriers (including water repellents) and drainage are standard defences. In your case, after 100 years of compression, settling, and weathering, repointing may be necessary. A consolidation treatment for severely weathered stone might be on the table. Areas with heavy rainfall typically have acidic soil. Acid [weak sulfuric] chemically weathers and degrades masonry. Deal with excess soil moisture, and don't supply it from the surface or allow it to collect,
if it can be avoided.

Falling Damp: inane, ceptn' for ifn' ya got a creek in yur neck. Typically it's applied to chimney breasts, roof, gutters, leaders, and anything else above yur head bone.

Since the sales office missed them, I'll add a few interior damp definitions of my own. Tea kettle and coffee damp, Shower damp, Biffy damp, Flora and fauna damp, and Too stupid to close the window or damper damp. [This could be the start of a new damp spin-off industry].

Summary: Repoint degraded mortar. Possibly treat severely weathered stone with a consolidate. Apply vapor barriers (above and below grade... liquid or otherwise) and caulking as required. Move surface water away from the foundation (starting at the roof level) and use a drainage system for subsurface water. For condensation move the air, dehumidify it, or raise the temperature of the surrounding surfaces.

When all else fails, remember, this is a box. It is not a rocket ship. And, dealing with the majority of water related problems is not rocket science.

Sales humor:
The ground water table rises just beyond the foundation. Wet soil transfers mositure to the masonry. Now we have penetrating lateral rising damp. If it rains, we have penetrating lateral rising and falling damp. If the wind blows we have penetrating lateral rising and falling horizontal damp.
 
 

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