On buying our last (ground floor) flat, built 1890s the 'survey' showed rising damp around the entire outer skin of the place. Now, we couldn't buy without making a commitment to rectify it because the bank threatened to withold a portion of the mortgage.
Now, having recently seen 'surveyors' in action - the buyers 'surveyor' took 8 minutes to 'survey' it when we sold it and flagged up damp again
- apparently the recent chemical damp-proof course had holes in it which we had to pay to have fixed.
Yes, we had to pay because the 25 year guarantee we had was worthless since the company had mysteriously folded and re-surfaced under a practically identical name... We found out later how common this practice is.
Aaaanyway, the damp meter that the guy used was "a professional one" and showed damp in places my obviously amateur one didn't.
Now, the questions - how good are damp meters, how are they calibrated, does it take an expert to use one ? Is this whole damp thing just a scam between the suryeyors, the bank and the damp-proofing thieves ?
Damp meters are useless. This is because they measure the surface damp, which is almost always caused by condensation. They tell you nothing about the overall state of the wall.
I know, 20:20 hindsight . We were young, foolish and trusting (now old, wiser and cynical).
Still, worth letting everyone else know s'pose.
It was amusing when the guy from the original company turned up to give us a quote. Man, he must have had b*lls like melons to think he could get away with that. SWMBO went to town on him.
There are two sorts, the electric ones simply measure resistance and were designed originally for the quick assessment of moisture content in timber during seasoning and after kiln drying. In this role they are relatively accurate as the conductivity of different types of wood relative to their water content is pretty constant. Rather than displaying resistance the scale could be marked in water content for different wood types and a numpty could be let loose with one.
At some stage someone decided they could be used for measuring moisture in walls. At this they are almost completely worthless as the resistivity of wall material is variable and not proportional to moisture content alone. Funnily enough the damp proofing "industry" is something almost unique to the UK, "rising damp" and the worthless chemical injection "damp proofing" doesn't appear to be an issue anywhere else in the world.
The second group of measures involve taking a sample from a wall using a core drill, weighing it, drying it and weighing it again. These need a trained operator, will give fairly accurate readings and invariably find little or no evidence of "rising damp"
See
formatting link
(lots of other information on that site as well)
For wood. Fir at 7% moisture will show a resistance of about
22Megaohms falling to 0.5Meg for 25% moisture. Walls are anyones guess.
Yes, to do it properly. Given to the usually salesgrots with an IQ in the low 20's found in the dampscams there are an endless number of errors they can make by accident (never mind the deliberate ones) including:-
Diagnosing condensation as rising damp. This is the most common as condensation will occur more on lower (cooler) parts of the wall than higher up. The numpty with the meter will find higher readings further down the wall than higher up and declare its "rising damp".
Conductive wall materials. Many old houses used clinker blocks (breezeblock) derived from coal or steel industry waste. This is naturally conductive and will always show "damp" even when bone dry.
Empty house. Any house which has been empty for some time with no heating on (other than during summer) will have damp walls. As the heating is turned on the moisture content of the air rises and moisture condenses on the walls increasing (temporarily) their moisture content. The numptymeter will show increasing damp readings at lower wall levels (I've seen a Rentokil "surveyor" diagnose rising damp in a first floor bedroom using this "varying resistance" assumption. When asked how it got 15ft up the wall he declared that damp was cunning stuff).
Those I have seen are nothing more than electrical resistance meters. They can give a fair idea of the moisture content of timber (for which many are designed it seems) but tell you lots of random stuff you don't need to know about walls (like they are built of electrically conductive (high carbon content) cinder blocks that always look damp to a meter, or you have a foiled wallpaper)
Calibrated, yeah right ;-)
expert con artist perhaps.
Smiley not required IMHO - you hit the nail right on the head.
Damp meters do have some use on walls, but its not what its generally interpreted as. The only thing they can do is prove dryness with a high R reading. A low R means more or less nothing,as it has a number of causes: damp problem, damp but no problem, normal transient surface moisture, conductive building materials, salt contamination with or without damp (eg due to a drink spill), conductive foil vapour barrier, fingers across meter contacts, and so on.
Forget the scam merchants, look at the wall and tell us from that if you have damp. Do you have salt crusting with plaster blowing? Do you have water dribling down the wall? Black mould on the wall? If you've got none of those, the walls dont have a damp problem.
What about solutions? Since these salespeople say whatever suits them, I'd try inviting another one in for a free damp survey. And mentioning when theyre about to start that youve had some nonsense talk of damp, are angry about it, and will do a core sample if their check doesnt confirm the obvious fact that there is no damp problem. This is likely to frighten them into behaving and giving an all clear, then you have evidence to give to the bank that there is no damp problem.
Its a joke that lenders tke this stuff seriously, but they do. They havent seen the house and dont know what state its in, and want to avoid any risk to themselves. If they had more integrity they'd recommend a genuine damp expert check up on reports of damp, though these are few and far between. And they'd warn surveyors that they recommend follow ups of such disagnoses with proper checks, and will not employ them in future if they falsely diagnose damp. But its easier to just sit and watch the customer get scammed.
Easily the best answer to a question I've ever had on a newsgroup. Thanks Peter.
The meter used in the buyer's survey had two prongs and was clearly a resistance type. It's as accuracy and functioning sounds similar to that of a Ouija board.
Considering the amount of money, time and effort it cost us I'm simply staggered that the banks put so much insistance in pursuing the findings of such things. Not to mention the fact that it could have sunk the whole housebuying chain.
With both "insurance backed" and Credit Card claims you will I have no doubt be absolutely amazed to find out that most of _their_ surveys show no trace of rising damp but lots of condensation - which isn't covered by any guarantee :-)
It's definitely a scam, in the sense that it is not dealt with properly, and the DP companies take advantage of this.
Lenders and buyers have a habit of suing surveyors, so the surveyors cover their backsides with these meters which dont tell the whole story.
To be honest, there is no collusion between any of the parties, and we probably get the surveys we deserve.... just like we get the estate agency service we deserve......
I was about to get into giving you a detailed response to this post when I notice Peter Parry had provided a link to the page on my site that covers more or less everything you were asking - almost.
To the specific questions above however: a good damp meter is very good but the way it's used is crucial . Unfortunately the majority of surveyors, both chartered and damp-proofing, use them incorrectly. Electronic moisture meters can only indicate moisture, they cannot quantify it, and this is important because the vast majority of older houses have a degree of dampness, which in most cases is completely insignificant, in the base of their walls. It'll have been there since
- in your case 1891 - and it'll be there till 2891, without doing any harm whatever. As these extremely sensitive meters will detect the smallest amount of moisture, the poor old punter is on a hiding to nothing.
It isn't a scam between the surveyors the bank and the others. It's a result of litigation. As someone else pointed out on this thread, chartered surveyors don't want their PII premiums to rocket; so they don't take chances. When their meters show 'damp', or sometimes, even if they don't, they slope their shoulders and tell you to get a 'specialists' opinion. And this is the unbelievable part of the whole debacle; because what they are actually saying is "go and ask the opinion of someone who makes a living by inserting damp proof courses. He might not want to earn any money today and, instead of giving you a 'quickie' (in more senses than one), he may even take the trouble to ascertain the true cause and severity of any dampness and advise you that his services won't be of much help to you. I know that to do this it will take him at least an hour and a half and probably won't make him any money, but you just might get lucky. I don't really care one way or the other though, because it won't be my insurance policy that gets caned if it all goes wrong. Bye Bye"
If you think I'm cynical you're absolutely right, but then again, I get asked every day whey I don't do 'free' surveys. But that's a different story!
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