Rising Damp - A Myth?

I wonder if that's why the damp-proofing people always put a cement render on the first metre of a treated wall. They say it's because the treatment affects plaster, but it may be that it stops the wicking effect if their treatment fails (assuming it was necessary in the first place).

My

Reply to
GMM
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hard brick with string mortar no.

try soft Tudor brick and lime mortar covered in plaster, and watch the salts come bubbling out.

If it doesn't exist, why do we use DPMs and DPC's?

Reply to
The Natural Philosopher

I saw test in some brickwork showing 10 inches or so. That's about how high mine got.

What DPC would that be then? :-)

Reply to
The Natural Philosopher

When I purchased my current house the "surveyor" diagnosed rising damp in the outside kitchen wall. If he had looked a bit harder he will have found that the wall was shared with an outhouse with some missing roof slates. When it rained the outhouse filled with water to a foot deep. Replacement of a few slates and removing the plaster from the wall cured the rising damp.

The diagnosed rising damp to the front of the property was cured by replacing the sponge like wood at the bottom of the window frame.

Reply to
alan

the undiagnosed rising damp in my chimney stack and internal walls was cured by demolishing the house to reveal the lake that was formed under the floor when it rained. I stopped the carpets rotting using plastic bags under the carpets but I couldn't stop the plaster blowing on the walls..

MOST of the house had been injected, but not the internal walls.

There was no damp course., There wasn't much in the way of foundations either.

I later learnt it was a converted 17th century dairy.

Reply to
The Natural Philosopher

Fry was simply quoting the surprising opinion of some industry professional= s.=20 Most of the houses that were 'affected' by it were probably built with lime= mortar, which is apparently much more permeable than the cement stuff. Put= ting any sort of cement render on old buildings seems to trap moisture that= would otherwise evaporate harmlessly.

There must be some sort of test, like chromatography, that would show whi= ch way any moisture was heading.

Reply to
Onetap

A few minutes with a damp meter can show damp anywhere. Doesn't tell you if it is rising damp. Or just moisture for whatever reason.

Reply to
Dave Plowman (News)

You can buy a damp meter very cheaply and muck about with it yourself. I have hired the equipment and injected my own chemical DPCs and seen the difference visually. (Confirmed by the meter.)

All old walls with lime mortar. (Coincidence?)

Reply to
harry

Reply to
Mark

I do seem to remember a report by the Building Research Council about 10-12 years ago (maybe more) saying that although rising damp does happen in some cases, the vast majority of reported cases are in fact condensation of moisture on the walls. The moist damp air apparently sinks, and thus condensation happens in the first couple of feet. They had a demonstration of various building materials sat in a shallow tank of water and were tracking how far it would rise up. This may just be a brain fart - but I also seem to remember 'Tomorrows World' picked up on it and showed the demonstration.

AWEM

Reply to
Andrew Mawson

My Victorian semi has lime mortar. When I bought it in the '70s, it was common for the lender to require a damp and woodwork warranty. Inspections were free, so I got several. Most wanted to fit a chemical damp proof course which would also entail removing all skirting boards and plaster up to about 1 metre and re-plaster with waterproof mortar. Thus ruining the beautiful high Victorian skirting, which would be impossible to replace as was.

All their damp meters of course showed damp. But non of the old wallpaper did - in a house without central heating. Have you ever tried sticking wallpaper to a truly damp wall?

I eventually found and used a firm who were happy to just sort the woodwork, and who understood and was honest about damp. They said in a house with a cellar, the damp stays down there. ;-)

Reply to
Dave Plowman (News)

IIRC this came from a Jeff Howells column in the Sunday Telegraph a few years ago, didn't it?

See:

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Reply to
Lobster

I've got a 2-foot-high brick wall around my front garden, and that's got a DPC!

Perhaps it's just seen as a requirement for any brick wall that starts below ground level.

Reply to
BartC

Perhaps someone on QI might have queried that. They're supposed to be intelligent aren't they?

Reply to
stuart noble

I've just seen a wall with what looks like flowstone on the bricks - caused by the gradual evaporation of lime-rich water, leaving the lime behind. It stops cold at the damp course, so that one is doing something useful.

Andy

Reply to
Andy Champ

But how many times do you hear of "damp treatment" companies claiming that the original DPC must have failed - and hence needs an injected replacement? When you consider in most old buildings the DPC was a layer of slate, it makes you wonder when it stopped being slate and transmogrified into sponge cake or whatever they think it is now!

Reply to
John Rumm

but it is slate bonded with mortar with overlapping slates. It's quite possible for a bit of vegetation (moss for instance) to bridge the slate nad shoddy workmanship can easily leave aa bit of mortar across the slate layer. On the outside, soil can also build up against the wall above the dpc.

Reply to
charles

While true, neither of these mean its failed or a likely cause of rising damp.

Soil piled against a wall is a case of bridging, as is moss etc. In either case removing the soil or moss will fix the problem.

A wall that was built badly in the first place would have always been damp if that were the root cause of the problem.

Reply to
John Rumm

my old house was soft tudor brick + lime mortar laid on wet clay.

Injection had solved MOST of it. Too late to save the timber above its true.

Reply to
The Natural Philosopher

I don't think you would claim that the original DPC had "failed" in that case though - it was just never there.

Yup sure, when you have genuine rising damp rather than some other cause, and no DPC at all, then an injected one will probably be a massive improvement.

Reply to
John Rumm

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