Rising Damp?

Cash-Is-King

This is very simple and it will save you a lot of money.

What you have done seems perfectly logical but it is flawed thinking and I will explain why.

You have damp so you thought, get a damp specialist to confirm or deny this. I am sure they did the survey for free, saving you a few bob? Wrong.

The question you need to ask here is, what line of business is the specialist in? He wants to carry out a damp proof install, why would he try to argue against the surveyors assessment? Answer, he will NEVER say the surveyor was too cautious/the damp is more localised to a small area, you have no rising damp issue! It would be commercial suicide.

The right way to think about this is this... You have suspect damp. Get an INDEPENDENT QUALIFIED expert in, he should use a Speedy Carbide meter as opposed to a battery operated damp meter. He is there to give fact. He isn't there to give further service. Yes he may charge a couple of hundred quid but wout you rather have an expert report for £200 to say you should open your windows more or pay some rogue £1500 for something you dont need?

I am a a professional consultant and I know there is a lot of mis diagnosis of Rising Damp. Buyer beware etc

David_Aldred

Hi,
Good answers from everyone and hope the following may help a little as a general comment:

Your surveyor noted a dampness problem and asked you have it investigated. He appears not to have commited himself to what the moisture source was.

You have asked a company selling damp proof courses to diagnose the moisture source. They diagnose rising damp and for you to pay them to install a new damp proof course - gosh there is a surprise. I wonder if they wrote out all the other moisture sources that could be contributory and to recommend these be resolved first then to monitor for drying down before considering further investigation of the dpc as suggested by BS6576 which gives guidance for those looking at dampness and whether to consider if a chemical dpc is justified.

The house in question will most likely have been built with a damp proof course probably in slate or bitumen or some other material that does not disappear. The property has already had another damp proof course installed so it already has two damp proof courses.

So if the two dpc's have failed how did that occur? An original slate or bitumen dpc may crack with settlement of the house but how much dampness would come up through such cracks ? It would not be full wall lengths. So even if cracked (and we are not saying it has even done that) we have a tiny amount of rising dampness up through such cracks but then we have a second chemical dpc that has lined the pores of the masonry and made them slippy to resist moisture rising up through the wall by capillarity (rising dampness). Yet it is still damp - don't tell me the previous contractors dpc was no good and theirs will be much better........mmmm.

The contractor has guessed and not proved the problem is rising dampness. Rising dampness can only be proven by laboratory analysis of wall samples as set out within BRE Digest 245 and even then you would have to rule out other moisture sources to external walls and around chimney breasts which may not be easy to do.

An electrical damp meter will give a high reading to a base of the wall for a whole number of reasons other than rising dampness and all they do is highlight areas of concern that should be further investigted. Did this contractors report have suggestive wording of "indicative of rising dampness", or "of a pattern associated with rising dampness", or some other phrase all of which is short for "we took a guess at rising dampness because I am paid on commision to find work for the lads and my boss will fire me if I keep coming back with no jobs booked in".

Recalling the contractor who installed the second damp proof course (dpc) they will probably undertake a carbide meter reading on site and hoping that they do not have to do any further work for free hope the reading is under 5%w/w. If it is below 5%w/w they will deny the problem lies with them and blame penetrating dampness / occupancy induced condensation. If it is over 5%w/w they may offer to re-inject which from experience is unlikley to resolve the problem. They will probably be charging for the re-inspection unless the reading is over 5%w/w and issue guidance notes on condensation for occupiers.

At ths point you probably would either accept their findings and continue with the purchase, back out of the purchase or argue the cost of the works your dpc contractor has suggested which the seller will deny is necessary arguing the re-inspection comments from the other contractor.

Any comments without seeing the case are speculative other than those which are a matter of fact.

1. The original damp proof course the house was built with will probably be generally intact. The second chemical dpc was probably installed through misdiagnosis from a contractor selling damp proof courses. Because they failed to resolve the true reason for the dampness the problem has re-asserted itself. Tests for dpc failure will likely come back negative since there is likely nothing wrong with the dpc the house was built with though this would require tests to confirm.

2. A carbide meter test on site is taking a sample of wall and mixing it with carbide dust that reacts with water and gives off acetylene gas which pressurises the container into which it is placed.The pressure is measured on a gauge. BS6576 states readings over 5%w/w should be further investigated but in truth it depends on the material being tested and some bricks such as a hard dense accrington nori can be wet at only 1%w/w.

A carbide meter test on site gives a total moisture content value that is comprised of moisture absorbed from the air (called the hygrsocopic moisture content) and moisture from any other source. Used on site in this way it does not split the value and walls can give very high carbide meter readings purely from hygroscopic moisture content in the sample if the relative humidity is high enough.

Given that there is likely nothing wrong with the original dpc the house was built with the contractor is hoping to be on a winner here because although he will have diagnosed dpc failure with an electric damp meter when flogging his chemical dpc, he is now re-inspecting using a carbide meter and suddenly he discounts the electrical damp meter readings and shows you a low carbide meter reading (hopefully). Given the original dpc should be effective the carbide meter reading he is hoping will be low although it could well be high for other reasons such as hygroscopic moisture, penetrating damp etc. If he gets a high carbide meter reading and he still hasn't spotted the true reason for the high reading he will prob offer to re-inject which can be done in a couple of hours on a friday afternoon. What he never ever wants to offer is to re-plaster unless he really has to because that could take his plasterers off another job for a week which is a big loss and give him a major headache.

3. Your best option is to get an independent qualified opinion not one from a contractor who should look for all the moisture sources including not only rising damp but penetrating damp, blocked cavities if cavity wall construction, damp / wet sub floor voids, gaps between solid floors and walls, contaminated plaster and dew point analysis etc. They should check if the previous contractor worked to BS6576 which refers to chemical damp proof courses. Out of preferance ask the seller to go halves on such a survery as it is in both your interests to get to the bottom of the matter.

4. If the previous contractor is found to be at fault even with matters of clearing cavities / the quality of their re-plastering / not resolving issues to timber floors / solid floor and wall joints they should be asked to re-treat. The risk is that re-treatment work for free is usually "Friday afternoon" work to be done as quick and as cheap as possible at a few weeks / months time at the contractors convenience to get the customer off their back. The standard of such work is sometimes poor under such circumstances. This being the case you might want to insist on forgetting the previous contractor and going with a builder you can trust to sort out the true reasons for the problem as recommended by your independent surveyor in your area specialising in these matters as suggested by others. When you are dealing in thousands the relatively small cost of the specialist survey is worth the outlay for all concerned.

Hope the above helps, kindest regards, David Alded independent dampness & timber surveyor

jetsetwilly_2

Thank you for your detailed opinion.

I am torn between the independent survey, and just going ahead anyway and maybe having a bill later down the line.

You are right in the fact that damp proofing has been done before, so that gives me a degree of confidence that it isn't rising damp.

And again, correct in the term used 'there are signs of...."

Is there a directory of independent surveyors anywhere?

David_Aldred

Hi - please have a look on the PCA (Property Care Association) website under headings of find a member - there you can select to find a contractor, a Freelance Surveyor and a Consultant. The last two are independent and you should be able to find one or two within travelling distance of you. The comments are not meant to be an effort to convert folk as everyone has their own opinion on these subjects but just to open their eyes a little to what goes on with this game and you must always go with what you feel is best for you in your particular situation. Kindest regards, David

jassco

jetsetwilly wrote: »

So what are you planning to do?
I think the damp spotted for me was also by kitchen/porch. Property has been renevated, looks very good, but I wonder if there has been paper over the cracks?

Guess, all the surveys in the world won't give a full answer. Until you move in and live there, you won't know everything

I've asked the EA to arrange for a builder to go in and give me a quote on the work. Once I've got this initial quote, I'll then get someone else to have a look and give a separate quote. If the vendor also wants to get a quote from a builder they know, I'll happily take it into account alongside the two other quotes and take an average. Similarly for me the house has recently been decorated so couldn't see any signs when viewing.

When we've got a figure I'm happy with to do the work, depending on price we'll ask for a contribution from vendor (as to how much completely depends on what the builders say)