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Conservatory Roof/Damp proofing

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Sunday 8 April 2007 8.34pm
Rising damp does not exist.

It is an invention of 'specialist' 'damp-proofing' charlatans who want to take lots of money off you.

Penetrating damp is quite another matter. Water naturally moves from an area of high [water] concentration to an area of low [water] concentration. So if you have a basement the water will naturally move into the house from the surrounding ground.

Live with it. Put in some air bricks; turn on the central heating. Put in an extractor fan.

Central heating does not 'draw' water into the building; rather the reverse. Modern, hermetically sealed, living generates huge quantities of surplus water (power showers, kettles, gas fires, breathing humans).

Basements were never designed to be lived in - least of all as a sealed, separate 'house'. Sarah writes a lot of sense: "The surveyor we used effectively said that if we were worried about damp we should not buy an old property with a semi-basement. However he pointed out that the propoerty had stood for a long time and so was unlikley to fall down."
Tuesday 10 April 2007 1.18pm
Well as a fully paid up 'damp proofing' charleton myself, who spends lots of other peoples money protecting their buildings against water ingress, it is a surprise to find out there is no such thing as Rising Damp. Particularly as I can refer to the British Standard BS 6576 'Code of Practice for diagnosis of Rising Damp in Walls' 2005, or more usefully for Victorian Houses, the British Research Establishment's 'Treating Rising Damp in Houses. Good repair Guide 6' 1997. when asked how to deal with it.

Rising Damp ( and it really does exist )will travel a metre or so above floor level within the brick walls and then evaporate into the building. As the moisture is drawn into the room it will leave patterns of salts on the plaster surface leached from the plaster as the water travels through. It will eventually cause the plaster to crumble away. It is rare but not unusual in Victorian houses, particularly those built before 1875 ( I think ) as these would not have had a damp proof course in the construction.

What was acceptable to the Victorians is not necessarily acceptable now, and therein lies the problem with the damp. It comes down to what level of compromise you will put up with living in an old house, and in a changing world what you believe will be acceptable for the next buyer.
Wednesday 11 April 2007 11.48am
Tell me, how do you detect rising damp?
Wednesday 11 April 2007 12.25pm
by a process of elimination usually

Damp in houses is more often caused by condensation and/or penetrating damp from an exposed wall.

Rising damp would be the probable cause of a damp loadbearing wall in the centre of a house. It would have a pattern of tide marks parallel with the floor which when inspected would be crystalline in nature. The plaster below would have lost its nature and be crumbling away. There would be no evidence of damp above, apart from maybe some secondary condensation dampness due to the wall being cooler.

It would be hard to identify on a north facing solid brick wall for instance because brickwork walls are not waterproof and will always show dampness within the brickwork if tested. And north facing walls have a slower evaporation rate.

In basements that are predominately dry the breakdown of the wall tanking would be more likely, with water tracking to a weak point which might be the floor/wall junction
Wednesday 11 April 2007 3.19pm
>>>by a process of elimination usually

So... if having eliminated the obvious likely causes you still cannot justify the cause of damp, you attribute it to 'rising damp'. Clever!


I presume that you use a damp meter?
Thursday 12 April 2007 12.49pm
Falling somewhere in the middle, what I was trying to say is dont asssume rising damp. It can be all sorts of things. Hence using a reliable builder or a sensible surveyor. (Trick here is to walk round with them, even on a house valuation, as they are usually prepared to say more than they will ever put on paper.)

In another property, which we bought in the dark as the electricity had been cut off, damp that showed up in the valuation survey as rising dame from the back wall of the Victorian extension proved to be a pipe leaking under a concrete floor.

So do I agree with both Rick B and Mapmaker? Make sure you elimate everything else before assuming rising damp.
Thursday 12 April 2007 1.33pm
We've now had an offer accepted on a new build with garden and had our valuation for mortgage done today. Exchange and completion within 28 days. No worries re damp etc so we are happy!
Thursday 12 April 2007 2.31pm
But potential problems with condensation. Damp in another form. Some new build properties are so sealed that there is nowhere for the moisture to go.

I am being mean. Congratulations. Where is it?
Thursday 12 April 2007 6.44pm
Silence from our 'expert' I note. And that will be because capillary action just doesn't work that way in a wall built from bricks and mortar. Damp can certainly track up between bricks and plaster - so yes, it can rise. However, these damp-proofing charlatans who diagnose 'rising damp' treat the rising damp by injecting the brickwork with a 'chemical damp course'.

Several problems follow:

1. The chemicals used are highly toxic. You really don't want them in your house if you plan on living there.

2. The problem is not with the brickwork. The problem is with the brick-plaster interface. Therefore... injecting the brickwork with a dubious chemical is not a solution to the problem.

3. Injecting brickwork... how on earth do you inject brickwork? Bricks are pretty solid things; you can't inject dubious substances into bricks and expect the bricks to absorb said substance!

4. The work will be guaranteed. (Just like timber treatment.) But these treatment companies have a nasty habit of setting up a new subsidiary company on a regular basis to make these guarantees - so your guarantee becomes worthless as their previous company, who guarantee your work, is liquidated.
Thursday 12 April 2007 7.07pm
It's in Nunhead.

Mapmaker you are right re guarantees- that's what happened to my parents.
Until recently they had a 5 storey house in Hampstead including a basement that had been converted into a dining room and utility room.
The damp course had been installed by previous owner and it had a 15 yr guarantee.
Of course the damp was still a problem and the room was very cold. They just could not not get rid of it. The firm who did damp proofing found some way of getting out of honouring it and my dad said those guarantees aren't worth the paper they're written on.
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