Advice Needed RE Damp

[Mark A]

After completely renovating our house about three years ago we noticed some damp in one particular room. At first we thought it was condensation so placed a dehumidifier in the room but over the past four or five months some wet patches started to appear.

We called back the company who installed the DPC and they said to take off the skirting (which I did tonight) and see whether the plaster extends down to the concrete screed underneath the pine T&G floorboards. They said if it touches then that is the source of the rising damp, but if it doesn't then the DPC may need to be redone in parts.

When I took off the skirting the back is wet and covered in green and black mould. The wet patches on the wall extend max. 30" above the skirting.

We would like to be armed before calling the company because they are reluctant to accept responsibility.


Any thoughts on this would be greatly appreciated.

Cheers,
Mark

 

[RogerBoyle]

Was the plaster touching the floor ??? it shouldn't be

things to check
are there any pipes that go underground or along the wall in the vicinity of the damp you may have a leak
Is there an external door or window near the damp as water could be wiking its way in

if not then usually there are 3 reasons for the damp
1. your Damp course on the brick work has failed
2. Your DPC under your flooring has failed
3. or more unlikely though still possible Cavity wall insulation has dropped and is allowing the damp to track over

You could always hire a moisture meter from tool hire place.. that will give you an idea of the level of damp that you have got as well as a general direction its coming from
and then Get them back out to it

I cant see how they can say parts of the DPC may have failed as common practise is to use a single piece rather than lots of bits in the same room

 

[Mark A]

Was the plaster touching the floor ??? it shouldn't be

things to check
are there any pipes that go underground or along the wall in the vicinity of the damp you may have a leak
Is there an external door or window near the damp as water could be wiking its way in

if not then usually there are 3 reasons for the damp
1. your Damp course on the brick work has failed
2. Your DPC under your flooring has failed
3. or more unlikely though still possible Cavity wall insulation has dropped and is allowing the damp to track over

You could always hire a moisture meter from tool hire place.. that will give you an idea of the level of damp that you have got as well as a general direction its coming from
and then Get them back out to it

I cant see how they can say parts of the DPC may have failed as common practise is to use a single piece rather than lots of bits in the same room

Thanks for your reply.

I didn't mention the external walls are 2' thick stone and the DPC was injected. However, there is no access to the exterior of the room which is affected by damp due to a neighbour's outbuilding (something which would never be passed now) so the DPC was only injected from the inside there.

There are no doors or pipes anywhere near the damp, and we've replaced the silicone around the window only recently yet the damp is still present.

Cheers,
Mark

 

[carlb40]

The outbuilding is more than likely the cause of the damp. Have they got sufficient airflow between the 2 buildings? How do they discharge the rainfall?

 

[RogerBoyle]

Sorry where I have said the DPC under the floor I meant the DPM ( damp proof Membrane)

I take it part of the neighbors outbuilding and your external wall are the same ???
If so are the floors of a similar level ???
do you have a DPM under the wooden floor and has it been taken up the sides of the walls higher than the injected DPC (tanked)

I do tend to agree with carlb40 though that it is most likely coming from the neighbors outbuilding

Roger

 

[Dusty]

Evening Mark
Sorry to give you the bad news , but the injected DPC will be totally useless and wont work . Trust me , My brother inlaw owns a very successful damp proofing company and I worked along side him for 6 month and he does my work , I gleened alot from him and one thing he never did was inject stone walls unless directed to and had in writing that the customer understood it carried no warrantee !!!

The reason it will not work is simple , an injected system works on saturating the substrate ie brick . with the proofing system , wether water or silicone based . It is the reason you see on houses a row of holes , two per brick all along one course . The bricks are drilled and the injection rods fitted and then the pump pressure the fluid in to the brick and forces any moisture out and seals the whole brick and the joints either side of it . You can see happening on softer bricks . This works by creating a solid barriers horizontaly .

With a solid stone wall you can not guarantee that the whole of each stone has been injected as they vary in depth and as the wall was built there would of been voids in the middle that were filled with rubble etc and these can not be injected .

Damp will rise up to 1400 mm high in a wall just through capillary action alone , let alone when under pressure . The only true way to deal with damp in a solid stone wall is to tank it . This where you need to strip the wall back to stone to a minimum height of 1500 but to be honest you might aswell work up to the ceiling , I always do otherwise you can end up with an expansion crack . The tanking systems vary depending on the manufacturer . I / we use Sovereign and the system is .....

Scratch coat with SBR mix
2nd coat if needed with in 24 hours
tanking slurry / heydi
Thermal plaster / Renderlite
Finish plaster .

It is not cheap but it is something worth doing properly once only .

I hate to say it but I doubt your warrantee is worth much .

This is there website ....... http://www.sovchem.co.uk/tanking/hey-di-system.html
Have a good read through their technical section on the damp proof injection fluids and they state hole centres of brickwork etc but no mention of stone work .

I do hope this helps and dont want to put a downer on it , but if they have guranteed the work they should be putting it right irrespective and if they fob you off , ask them who the manufaturer of the damp proofing gear is and call them they "should" send out some one who will advise .

Kind regards Sam

 

[RogerBoyle]

Dusty
unfortunately you have just confirmed my suspicians
Many thanks for the info

If memory serves if it is a party wall then you may be able to get your neighbour to pay towards it if you can prove it is coming from his side
Part wall act or something along those lines I believe covers it

 

[Lons]

I agree with Dusty, however you have absolutely nothing to lose by allowing the original contractors to try and put it right, as long as there is no cost to you involved.

I've never injected walls but have been involved with constructions where we have used outside contractors. Our last grade 2 conversion however we decided to install a dpm right from ground to ceiling level for exactly the reasons stated and no problems seen in 8 years (touch wood).

Virtually every old stone wall I have worked on has been constructed with inner and outer leaf of varying stone thickness and the centre filled with loose rubble. Had many an encounter with a stuck core drill due to loose stuff falling down.

Bob

 

[Dusty]

Glad to be of help Roger . I would agree with Lons on the tank it to the ceiling .

As far as the company asking you if the render/ plaster goes down to the footings ....1) it is highly unlikely as it is / was not done , as it would of bridged any possible slate dpc and would of been a waste of materials . , and most likely this is just their way of trying to avoid coming back on their warrantee / guarantee 2 ) It does not matter ...why ....this is the most important part ...........

........They surveyed the problem , recommended the solution , did the recommended work and then ......charged you for it .......and it didnt work , so therefore they Have to come back and rectify the problem at their costs and that does not mean you pulling off the skirting board and pulling up floor boards for them .

If they had done the it the tanking way , then there would not ( hopefully ) be a problem now . They charged you for a solution for which did not work .

If you get stuck , you could always call Sovereign and 'feign' being a potential customer and ask them for their recommendations of how they would propose doing it to gain their warrantee , but with out stating that some one else has had a go ! , see if you can get a reply by email and you will have enough paper evidence on the correct method .

I am only advising on working alongside a Sovereign approved contractor for a duration and him doing my work ( as it gets me the guarantee . I did my own at home about 7 years ago and have not had an issue to date .

Ultimately you can take up the guarantee with the manufacturer as that is who ( normaly ) holds it . But to do it properly you have to give them a fair chance to rectify it , normaly invite them to check it , give them an opportunity to then correct it in a timescale that is acceptable to both them ( not yesterday ) and acceptable to you ( not next century ) . Failing that , contact the guarantee issuer , and failing that , small claims procedure ( £50 ) but no body wants that on their record and you will need to provide independant reports / surveys to back up your claim and will no doubt cost you for their reports .

I would start by asking them this simple question which puts the ball in their court ........." how do you propose to rectify reoccurring damp that is still showing ?" But do not be tempted to throw any knowledge you have now as it may only put their backs up and make it more awkward from the off start . Just play it cool at first but dont be fobbed off .

It is their job to prove it is not their problem , not yours to prove it is !! I have not seen your house but given what you have said , I am confident in what I say ( not cockey lol ) .

As to your neighbors contributing , I dont know , but normaly it would be recommended to deal with both sides of the wall equally otherwise , if you tank your side , your neighbours will suffer worse . I dont know of any legality to notify your neighbours but if you were to knowingly cause damage to their property by your works it may cause you problems ££££

Good luck with your problem and do keep us posted as it will be interesting to hear their solution .

Kind regards Sam

 

[Eric The Viking]

You *can* inject stone walls -- I've done it with success -- but you inject between the stones, not into them (they'er usually not porus, but the mortar is). The exception being Bath stone, which is porous (although limestones usually aren't). In the case of the house I did, it was a Dutch mortar construction, which is essentially two faced stone walls (inner and outer) with a rubble infill. It used a huge quantity of Sovereign chemical, but it worked!

I don't trust chemical DPC companies, anyway. Round here the results are patchy at best, and our present house, which has engineering brick, was injected into the bricks (a while back), not the joints (black mortar) - a futile exercise. It's not at all uncommon, and tantamount to fraud IMHO. I'll have to redo it properly at some point if we stay here, as predictably, it's failing.

The other problems are that often the holes aren't deep enough, or clean enough to seal at the necessary pressure. Or they skimp during the actual injection, and don't let it pump for long enough.

Doing it right is nothing like as easy as they'll have you believe.

If it's done correctly, and it sounds like Dusty's brother does that, it will last for a long while and it is cost-effective. I cannot imagine though how you can do one side of the wall and not the other without it failing. You can drill from one side (deeper holes to do the farther side), but it doesn't work as well, because at some point one set of holes will drain the other set (if you're using enough pressure and chemical).

The biggest nuisance issues though are bridging the DPC, and condensation being mis-identified as rising damp. The other one, as mentioned, is a leak from somewhere. Dusty's quite right -- these people put it about that they're 'experts' and they sold you a fix for a problem, not a process.

Document everything carefully - lots of photos, and be non-agressive but firm about what you want - which is a fix!

E.

 

[Mark A]

Hi guys,

Apologies for the late reply - problems with Virgin Media....

The contractors called back last week and told us to hack off the plaster behind the skirting to expose the original stone wall. This afternoon they redid the DPC in the affected areas free of charge, which confirms that it must not have been done properly in the first place!

Eric - the DPC was done by this company the way you mentioned. Before this contractor, we paid a guy recommended by a neighbour to install the DPC. He drilled a nice neat hole in the centre of every other stone around the house! It almost came to the small claims court to get our money back!


I'll give it a week before I put the skirting back on to see if the problem has truly been rectified.

Thanks for all your advice,
Mark

 

[Eric The Viking]

Hope that's sorted it!

Make sure they use a properly waterproof render mix, too. I'm told the waterproofing powder additive is just a very fine flower to fill the voids in the cement, and I don't trust it on its own for this task.

You can add a fair amount of PVA ("Unibond") to the mix. It's not so much to keep the wall waterproof, but to stop dissolved salts migrating to the inner surface as the wall dries out (thus damaging your decoration). Don't ask me how I know (sigh!), but salts happily move through traditional paper and crystallise out on the surface, wrecking it in the process.*

I've used a dehumidifier in the past, The commercial ones work well, but the challenge is that drying too fast causes cracking in the skim coat, and encourages the salts to move to the surface. Once there, they're a PITA to remove - you might have to resort to polyurethane stain block (or sizing with a fairly dilute PVA solution) to get a surface good enough to paint/paper onto. So better if your render is pretty waterproof to start with.

I'd size with dilute PVA anyway for wallpapering. You can use paste, but in my limited experience you still get some 'suck', enough to make positioning hard, especially with lighter weight papers.

Regards,

E. (who can't stand painting anything, but likes papering!)

*If it does happen (over a few months) you can minimise the visible damage by using a soft clothes brush (shortish bristles) to remove the crystals. They need to be pretty dry, and you need to be pretty gentle otherwise you risk damaging the surface further. You won't remove the signs altogether though it just makes it a bit less visible.