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).
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.
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.
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.
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.)
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.
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. ;-)
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.
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!
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.
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.
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