Surveyor disagrees with damp proof people

27col

Another excellent post David. I don't know what we did without you.

dampdaveski

an excellent and generally informative post David,
However a couple of points

The contractor who recommeded the dpc four years ago will have done so on the back of using an electrical damp meter similar to the one your Chartered Surveyor has used. The meter is basically a battery with two wires leading to probes and the easier it is for the electric to run between these two probes when applied to something the higher the reading on the meter. If you stick your hand on the end of such a meter you will get a high reading but clearly your hand does not have rising dampness.


You strike me as the sort of person that doesn't make wild accusations / assumptions, yet you state exactly what testing equipment the contractor used to determine the original works, you may well be right, but for all you know he used calcium carbide tests / took samples etc,

Well we know the dpc contractor did not actually prove rising rising dampness when they said the property needed a new dpc. The contractor simply took a guess at this simply because that is what they are there to sell. If you pushed for detailed laboratory investigation the results may well be no rising damp is now present but the laugh of this is clearly the question is this because the original dpc remained effective and the new dpc was never required (i.e the damp was due to something else) or is it because the last dpc installed by the contractor is controlling previous rising damp?

You don't actually know that at all, you've made an unqualified assumption on your previous assumption because it fits in with your 'all contractors are theives' sales pitch

I hope the above helps at least give you some idea. Clearly without blowing my own trumpet one perhaps can see the benefit of having an independent specialist surveyor look at the problem rather than a general building surveyor or a dpc contractor looking for work (and then usually saying there is nothing wrong with their previous work). A list of such Independent specialist surveyors may be found upon the Property Care Association (PCA) website and look in the section 'find a member' and then select Freelance or Consultant (the rest are contractors looking for work) for one in your area to have a chat with. Hope this helps, kindest regards David Aldred Independent damp and timber surveyor.

As i've said before, you advertise on the PCA website because you're a freelance surveyor looking for work. Without 'blowing your own trumpet' you advertise yourself on here every time you post.
It's your slating of all preservation companies in virtually every post you put on here that is getting beyond irritating. The industry does have an awful lot of fools (bordering criminals) in it and it does need to be shaken up, but you painting ALL contractors as criminals and all freelance surveyors as angels doesn't really help to move the industry forward at all.

Anyway moan over, it's good of you to take the time to help bubbly, and the above excepted I think you have given excellent advice

DD

David_Aldred

Hi again,
Regarding a carbide meter mentioned in Dampdaveski's post this is another type of meter often used by damp proofing contractors and some surveyors. Typically a dpc contractor may have one for their re-inspections and in the right hands they can be a useful tool for the surveyor but perhaps some explanation of there use on site may be helpful in light of dampdaveski's post.

Say for example a dpc contractor recommends a damp proof course on the back of their electrical damp meter readings as discussed in my previous post. As indicated such a recommendation is a guess and not actual proof or confirmation of dpc failure. Then for example the client puts their faith in the dpc contractor and has the work the dpc contractor recommended and inserts the new dpc that the contractor was there to sell.

Now in this hypothetical example the client decides to sell the property at a later date and a Chartered Surveyor inspects with their electrical damp meter and finds high readings in the same areas as before. Remember the dpc contractor in our example recommended that their chemical dpc be injected on the back of such high electrical damp meter readings so now in our example the dpc contractor is in a bit of a fix if they want to avoid the client saying yet another dpc and associated re-plastering is again required but this time all free of charge as it is under guarantee.

What can the contractor do to avoid this additional work for free? Well initially they can deny the high readings are anything to do with dpc failure such as saying they are condensation / penetrating dampness related etc (which they may entirely have been due to originally if the reason was misdiagnosed don't forget). If this tack fails to impress the client they can charge the client to come back and re-inspect for typically around £100 plus VAT.

Okay says the client it's worth the £100 I'll pay up and they get the dpc contractor back who then produces a carbide meter. If you have never seen one do a google image search for one they look like a drugs kit with powder a flask and scales! They are basically a pressure flask with a gauge on the bottom. The contractor drills into the wall away from an outside wall and a chimney breast to remove a sample of it and then balances it to a known weight before putting the sample in the flask and mixing it with calcium carbide that reacts with any water present to produce acetylene gas (don't smoke whilst doing this or you will go bang) that pressurises the carbide meter vessel and you get a reading on the gauge.

The contractor is hoping (well praying usually) for a low reading (typically under 5%w/w) and to this they say hey presto the wall is dry and there is nothing wrong with the dpc thanks for the £100 and off they trot.

This of course begs the question why did they not use a carbide meter to test the wall in the first place which would cut the number of dpc's being put into houses through misdiagnosis by one hell of a lot. Clearly recommending a dpc on the back of an electrical damp meter reading yet re-inspecting with a carbide meter is moving the goal posts and the client quite rightly may feel put out as to thinking what was the justification for spending the money on the new dpc with a red light on an electrical damp meter and then ignoring the same red light at a later date when a carbide meter test is done? This is when the client has that sinking feeling that they realise the contractor did not prove there was anything wrong with the old dpc when they recommeded a new one with their electrical damp meter.

The story does not end there though because some people think a carbide meter used in this way is telling them whether or not rising dampness is occurring when in actual fact it is not doing that at all. Let me explain:

The sample of masonry put into the flask will have some degree of moisture in it absorbed from the air and possibly but not necessarily some from anywhere else. That 'anywhere else moisture' could be moisture from penetrating dampness, condensation, leakage, rising dampness whatever. The meter cannot differentiate between these moisture sources when used on site in this way and simply gives a TOTAL moisture value within which there might be allsorts of moisture as a component of it.

A carbide meter can give very high readings indeed simply from moisture absorbed from the air especially to properties where condensation within the fabric of the building and high relative humidity issues are a real problem. Some contractors will recommend a dpc again and again when they find a high carbide meter reading thinking it is rising dampness when it has turned out to be entirely composed of moisture absorbed from the air. (I can't understand it this house has had 5 damp proof courses and it's still damp says the contractor).

BS6576 the British Standard for chemcial dpc's remarks that readings on a carbide meter over 5%w/w usually require further investigation and a dpc contractor will often say to a client for example "ah the reading is 4.8%w/w the wall is dry we do not need to re-treat". This statement is rubbish and depends entirely on the porosity of the wall material being tested which can vary from one brick to another quite significantly and for example a hard dense brick can be wet at just 1%w/w total moisture content. The British Standard does not say all readings below 5%w/w are dry, it just says readings over this value should be investigated which is not the same thing at all. Hence you really need to know what you are doing with these meters, what the results are actually saying and where and when they are appropriate for use.

So how is rising dampness diagnosed? Well out of preferance once all other obvious sources of moisture have been resolved and the property allowed to dry down at a rate of 25mm wall thickness per calender month wall samples are removed up the height of the wall say at 300mm intervals for each and every wall under investigation.

The samples are sealed immediately in air tight containers and taken to our laboratory or somewhere similar where they are weighed on laboratory scales which are extremely accurate (and cost thousands to buy in case you are thinking of doing this yourself). The weight readings noted the samples are then placed in a laboraory oven for a period of time and all the moisture present in the samples is evaporated by heat form the samples. The samples are then weighed again. So now we have the original wet weight and the weight without any moisture. What we then do is place the samples in a humidty chamber for a period of time and afterwards weigh the sample again. This last process tells us how much moisture that sample will absorb from the air alone.

The smart folk here will see that we then compare the weight of the sample taken from the wall, the weight that sample is when baked dry and the weight of the sample when it has absorbed as much as it can from just the air alone.

If the weight of the sample removed from the wall is greater than that which it will simply absorb from the air then that amount of 'extra' moisture came from somewhere else other than the air. If we did all of this testing on an inside wall away form condensation / leakage issues then this 'extra' element of the moisture is likely to be from rising dampness so what we would then do is look for any salts in these samples. Nitrate salts and sometimes chloride salts are associated with ground moisture amongst other things (nitrates can also come from leaking drains and chlorides from unwashed sands / coastal exposure etc).

Doing this type of analysis we plot the results for each and every sample on each and every wall under investigation until we get moisture and salt profiles that can be compared with rising damp profiles to see if we have correlation. Be aware that if we were doing this on outside walls we would find it hard to differentiate penetrating dampness and other moisture sources from any rising dampness components.

From the above one may appreciate that this is destructive and bloody expensive to undertake in addition to very time consuming. The British Standard for chemical dpc's is well aware of this issue and also recognises that with the majority of UK housing stock built with a dpc that does not disappear and because rising damp is so difficult to prove the recommendatioin is to resolve all the moisture sources other than rising dampness and then monitor for drying down to see if the situation resolves before considering whether the laboratory investigation discussed above is justified to investigate if there is any rising damp occurring as a component of the problem.

Finally coming back to the comment made by Dampdaveski that I presumed the dpc contractor had not undertaken all of this laboratory analysis the answer should be quite confidently yes we can assume the dpc contractor will not have undertaken all this laboratory anlaysis at their own expense for a typical free survey for their own profit especially when they are trying to sell a dpc not justify why the existing one is fine.

Even if the dpc contractor had by some wild stretch of the imagination undertaken such laboratory analysis the dampness mentioned in this case is on the outside wall and the Building Research Establishment (BRE) Digest 245 which describes the process of laboratory analysis recommends not to take the samples from outside walls simply because if you have understood the above you would find it very difficult if not impossible to differentiate between the rising damp component if present at all and any penetrating dampness / moisture resevoir accumulated within the base of the wall.

So in the end we come back to the recommendations I made within my previous post to simply investigate the matter further by looking at how this property was built and how perhaps its construction has changed since that time which may albeit have been done with the best of intentions but which may have increased the moisture resevoir within the walls rather than reduced it.

I rest my case your honour :T

Kindest regards, David Aldred CSRT, MIWSc, CSSW, AInstSSE, Independent damp and timber surveyor

keystone

When all's said and done what we have here is:

a) A building surveyor applying (well most likely IMO) the CYA principle to avoid the prospect of a compensayshun claim. This environment, again IMO, rendering most pre-purchase surveys largely meaningless these days.

b) A DPC contractor protecting his back on work he did previously.

The two are unlikely to meet even halfway. So the OP either has to engage another independent survey or take it all at face value.

Just IMO.

Cheers

AGBAGB

Enjoying the posts

Bubblybee, If we distil all this down. Yes, there could be indicators of some damp but its obviously debateable. The dampcourse guarantee isn't going to help. The surveyor has covered his #rse. You need to decide if it's worth losing the house over.
Old houses do need maintenance, Often previous works (doubleglazed windows, cement renders/morta, non breathable paint, blocked ventilation, built up ground levels etc.) compound problems and might need putting right, useually with simple solutions. Is the "problem" as it is really a big problem? Or is it something for slight price negotiation with the vendor? You could end up paying a small fortune for someone to make definate, guaranteed decision for you.

bubblybee

Wow, thank you david, dampdavski and everyone else. I really appreciate the effort you have put into the threads. I think where we are from reading all your posts is buyer beware. There may or may not be damp, if there is some damp it may or may not be important at this time, because of the way the house is set up and because it is old we are going to have to budget for works in the future, But, as AGBAGB says, is it worth losing the house over. The answer is No. It's just we want to know where we are and if there is a BIG problem that this is understood now. Am I getting the correct message? I'm not really looking to negotiate on price, I think we are getting very good value for money, I more need to prepare for either fighting with the damp course people to correct work or plan for remediation in the future.

Is there anything I can do now to protect myself for getting the damp proof people to put things right in the future?

Once again thank you so much for being helpful.

David_Aldred

Hi Bubblybee,
You are right with your appraisal of the situation. In the meantime try and find out if the area that the new dpc was installed was also re-plastered and if so whether the dpc contractor did that re-plastering themselves or a third party.

Also request the original dpc survey report (th eone the dpc contractor should have done) form the vendor, the dpc guarantee and the dpc contractors sketch of the areas treated indicating how they were treated. In addition ask for a copy of the re-plastering specification and dpc injection system (if chemical system) from the dpc contractor that their dpc manufacturer requires that contractor to comply with in order for that contractor to be one of their approved installers.

I am not saying you would win a case or anything but these documents are required if you want to go down any such route in the future so better they are chased up now prior to purchase along with a copy of the re-inspection report from the dpc contractor for your file.

If the wall was re-plastered by a third party your chances of a successful claim against the dpc contractor themself drop off quite sharply in many cases. If re-plastered by the dpc contractor one of the first things I would do is see if that plaster is contaminated by salts / is to specification by sending the plaster and the specification to an independent laboratory experienced in this type of work such as UK Analytical (www.ukanalytical.com).

The dpc contractor may offer to do a plaster test in house or using their dpc manfacturer's labs but you may not know what tests should be required and obviously somebody truly independent may be better to give you piece of mind as it wouldn't in my experience be the first time a dpc contractor doctored the results of any such tests to make the client believe everything was fine when it was anything but.

The design function of the plaster is to hold back residual dampness and salts within the wall and if the plaster is damp then looking into compliance with the plastering spec is obviously a good place to start. In addition put the issue into perspective regarding hassle and costs - if it is 2 metres of a problem area you might as well just sought it out yourself. If it is every external wall then it might be different. Hope this helps kindest regards David Aldred Independent dampness and timber surveyor

AGBAGB

Bubblybee, I'd class major structural work as a "BIG" problem and the surveyor hasn't found any of that. If it's the right house at the right money a bit of possible damp wouldn't worry me. (but then I'm used to old houses)

Look on the bright side, It might be when you move in, heat and ventilate, the "problem" doesn't exist.

If it is real then you can start to investigate possible building related causes.

dampdaveski

at the risk of bumping this thread and going off topic,
David you've not actually responded to the points I made in my earlier post, yet again you've created a hypothetical situation where the nasty DPC contractor is eating puppies and mugging old grannies and the brave and mighty freelancer comes along and saves the day. You choose not to respond to the 'awkward' statements and tell us all about gravimetric testing.
for clarification awkward being YOU advertise on the PCA site, and YOU are looking for work on there just as much as any contractor, and most annoyingly YOU are advertising yourself on this forum.

Forum rule :9.2.2 post or transmit advertisements for or solicitations of business;

I've had this situation several times, a house goes on the market, valuer goes round and sticks moisture meter on wall my company has treated, we get call -(we don't usually charge for call backs). We have a look if there's no problem we confirm there's no problem and that the guarantee is valid, house sale goes through everyone is happy. just read through all the above posts to determine who could hypothetically (of course) be creating a mountain out of a molehill just to create some revenue?

David_Aldred

Dear Dampdaveski,
I am most certainly not advertising for work or seeking work from this forum. As I have said to you before I do not give the Company details on my post that I am employed by, I simply give my name, qualifications and profession so that people know the opinion given is from a person who is qualified and professional indemnity insured to give that opinion in the matters discussed which are hopefully helpful to those that posted the query and for persons who choose to read that information.

Failing to post ones name and profession immediately calls that opinion into question as to whether it can be relied upon or not. For instance a milkman (sorry no offence intended) advising on here how to defend a person on a charge in court is perhaps not to be relied upon, so that is all there is to it so please do not read any more into that than there is.

The feedback in thanks relating to the information I have taken the time to give on this forum speaks for itself and whilst I appreciate that some of that information may not sit comfortably on the shoulders of those that are quite happy to take money off laypersons on the back of a high electrical damp meter reading then rubbish the same high reading at a re-inspection I am afraid I have no sympathy for whatsoever.

I can tell you that prior to becoming a surveyor my wife and I purchased our first house together and had to have a dpc installed as a condition of mortgage. On selling that house we had to knock thousands off our asking price to reflect the fact that yet another red light appeared on a damp meter of another dpc contractor. Many years later I was asked to inspect the same property and by means of investigation we established that the original dpc the house was built with was perfectly intact at point of sampling. Somewhere between all that I worked for dpc contractor and over a period of time discovered and learnt what tricks contractors sometimes get up to within the industry.

For instance drilling holes in walls to inject a dpc but never injecting the product to save time as the plaster would hold the damp back for a bit, putting fingers over the ends of electrical damp meters to show a high reading, pretending a mobile phone was a damp meter, back handers to estate agents to get enquires fed to the company, spraying insecticide onto the top of flooring but not the underside, turning loft insulation over to make it look like the loft timbers had been sprayed when they hadn't, pouring unused chemicals down drains, drilling holes in walls and never putting the wall ties in, taking 4x3" section joists out and putting 4x2" back, saying timber was pre-treated with preservatiuve when it was not, cutting a decaying suspended timber floor and dropping it into a sub floor void then concrete over the top, never issuing guarantees when they should have been issued, putting skim plaster into cement render to make it set quick, knocking out to clear cavities but never clearing the cavity just putting air bricks back, hiding a brick sample and shaking a carbide meter to look like you are testing a sample when you are not, changing info on 'in house' lab tests to suit so no re-treatment required, doing six inspections of houses a day including writing up to earn that nice fat commision. Lads scared they will lose their job so not doing half the work on the job sheets, lads balanced on triple extension ladders on their own 40 feet up drilling wall ties because the boss wants to save money on scaffolding hire costs.

Yes my friend I have seen a lot of this industry over many years so please do not try and educate me about bad contractors being in the minority because experience still shows it is the good contractors that are by far in the minority.

A contractor who does a good job and inserts a dpc when justified, sprays a property competantly when an active infestation of woodworm at signiciant levels is found and who ties a cavity wall properly if the wall can be saved has nothing to fear from the posts contained herein.

If you do not like the information, then please do not read my posts it's as simple as that - this is an open forum and I will not argue with you. You may disagree with the information and I may disagree with your information but that disagreement is of no consequence to me as the purpose of the forum is simply to answer the query of the person posting the question as best we might and you certainly cannot please everyone else reading that post but that is never the intention.

A contractor may whince and protest at the revelation to the public of how open the system is to abuse but the fact remains that sticking your fingers on the end of a damp meter and getting a red light does not confirm you have rising dampness and neither does sticking the same meter on a wall and getting the same red light only to be told after spending thousands on a dpc that the same red light found on the same wall years later does not then justify re-treatment if your the same contractor but if your a different contractor it means yet another dpc.

The industry as a whole needs to change if the public is to have confidence in the system and the industry will not do so in house by themselves without the public grabbing hold of the industry by the scruff of the neck and demanding change so that all work is environmentally, morally and financially justified.

You may well respond negatively but I have given the information that was needed to answer the original post to the best of my ability and been thanked for doing so by that person who originally posted which was all that was required and certainly not to debate my posts with you my friend. Kindest regards, David Aldred Independent damp and timber surveyor