De humidifiers not getting rid of damp!

paddypaws101

I had a leak from pipe work buried in concrete kitchen floor about 2 months ago. Plumber mended leak and replaced whole run of pipe through kitchen ( pipe lagged and laid in soft mix so it could move slightly ) Builder then laid self levelling screed over top to level. I have had a big de-humdifier and fan in the room for several weeks now...but when the damp firm came to check the floor readings where still sky high.
They say that either the damp proof membrane has been breached ( but had no obvioius damp prior to leak ) or that the new pipe is leaking ( water meter not moving )
Anyone had experience of a similar situation? One flooring company said to forget the dehumidifier and lay a damp proof screed across the floor which they say would sort the problem. Insurers and damp firm dont rate this idea and wont 'sign off' on the job on that basis.
It is an old house, though the extension is 70's, won't there always be some damp hanging around?

Wookey

Is the de-humidifier working properly? Run its outlet hose into a bucket so you can make sure it is drawing moisture out of the air on a daily basis, a decent domestic machine should draw up to a bucketful of water per night at this time of year out of a saturated room ie. new walls and floor just built/plastered.

paddypaws101

Yes the machine is working fine, I checked and it is pulling about a pint an hour...but the damp readings on the floor are not going down at all.

Wookey

Was the pipe that was fixed on heating or plumbing? Isolate and drain of whichever one it was and leave it for several days, you may also need to blow out any water within the pipework, if with the de humidifier still working the dampness doesn't disapear fairly quickly then there may well be a rising damp problem. If the concrete floor was chiseled out with a jack hammer of some sort then it may well have cut through the damp proofing, i would find it hard to believe it was this though as it would take your house to be situated below ground level for the machine to be constantly removing a pint an hour.

You say your water meter isn't moving, if it was a central heating leak and you are on a sealed system you would need to check the pressure gauge on the expansion vessel to make sure the system isn't loosing pressure.

It is mostly trial and error at this point to identify the problem, there is a couple of other options to check for a leak but they are best left to qualified plumbers.

paddypaws101

The plumbing firm is sending a guy round tomorrow to have a look. It ALL seems to be a bit trial and error....with me picking up the bills! Original leak was hot water from boiler, and I do understand that all the digging around could have torn plastic membrane and created a new problem. ( insurance love that idea as it gets them off the hook ) I have checked the new condensing combi boiler and it does not seem to have lost water.
I feel caught between the plumbers ( who I am pretty confident did a good job, but obviously I cant guarantee) and the damp company/ my insurers who are a bunch of numties!
It feels like the dehumidifiers are sucking damp into the kitchen rather than removing it!
Any other ideas so I can at least be ready for negotiations with plumber? (

Wookey

Other possibilties include kitchen sink waste pipe/overflow leakage, the prv on the combi boiler (assuming its a sealed system), a damaged sewer (where damage could have been caused by the digging up of the concrete and reasonably fresh water is leaking out from kitchen sink, highly unlikely this though as most sewers will run round the outside of a house and should also be far deeper than any digging that occurred). If tubolit/armaflex lagging was used check all radiator joints in the immediate vicinity, a leak at the bottom nut joint can travel down thru the lagging and show itself in the floor. If it is an old kitchen is your mains water pipe coming into the house running thru the floor in the kitchen, if so it would need to be isolated and ruled out. Thats about all i can think of at the minute.

dampdaveski

Paddy,
Is this a damproofing firm or a 'drying' company appointed by your insurers?
If there is not any physical dampness to look at on the concrete floor, the chances are the 'sky high' readings are being falsified by salt contamination of the floor, this is not necessarily a problem.
If this 'damp' company knows anything at all about identifying dampness they would use a calcium carbide meter test (or speedy test) to physically check a sample of the concrete. If they have never heard of this type of test, then they are half trained franchisee halfwits who should be dragged outside and beaten (joking about the violence). Another option is to use a less well known (but equally effective) test called the fugenex wallprotect test, this involves drilling a hole and placing a test 'stick' in the hole for 24 hours, if it reacts then the floor is 'wet' if it doesn't then it isn't! www.fugenex.co.uk more info there

hope this helps

paddypaws101

They are definitely a bunch of half wits who seem to know as much about damp as I do. They talked about drilling holes but were concerned that they would damgae the plastic dsmp proof membrane.
Plumber visited today and patiently dug up the whole area around pipe work he had replaced. After wrapping pipes in tissue we agreed there was NO leak from pipes, although there is definitely a damp area in underlying concrete surrounding the pipes which seems quite localised. Of course this is the area where the original leak was running for some time...but the de-humidifier has been pulling loads of water out of SOMEWHERE...just not the floor!
I will go and look up that specific test mentioned above.

dampdaveski

Hi paddy,
the dehumidifier will have been pulling moisture from all over your house if you didn't have the doors shut, as it's starting to get a bit colder now it will be dragging this extra moisture out of the air too. There is always the possibility that there is a second leak elsewhere under your floor (hopefully not though)

Damaging the membrane won't have caused the concrete to get damp in approx 2 months either, unless your kitchen is in a basement!
Sounds like it needs a dose of looking at
if you need a second opinion you could have a look at the PCA website www.propertycare.org most of their members are pretty good (i'm one of them )
Good luck