Rising Damp

S

simp

Registered User
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Hi All:-

Renovating an older house, so need to address a damp problem in the walls. Am getting some conflicting advice, though!

The previous occupant appears to have just put up dry-lining, which didn't work.

Our builder says that he'll remove the plaster, put a uPVC layer into the wall in front of the damp, and reseal.

The damp experts say they want to remove plaster and inject a chemical Damp Proof Course into the masonry.

My architect friend says that it's not rising damp, that it's spreading from elsewhere (bad guttering), and all you can do is address the cause and let it dry out. Moreover, injection of a DPC might just drive it further up the wall...

Your thoughts?
 

If there is a more obvious underlying cause like a leaking gutter or downpipe this should be rectified first before you consider chemical DPCs etc. In fact leaking gutters, roof defects, bridged DPCs (for example where floor beds bridge a DPC) damaged renders and spalled brickwork are quite often to blame when it comes to damp walls within buildings. These types of water ingress are relatively easy to diagnose and fix, especially if you have access to a moisture meter. I'd eliminate any and all of these possiblities before spending big money on chemical DPCs and the like (and they do cost).
 
We will need to replaster the wall where it has been affected by damp already, and get rid of sodden dry-lining, so the builder will be stripping back the walls anyway anyway...

And while the masonry is exposed, a DPC specialist has said that he'll treat the affected walls for €350+VAT, with a 20-year guarantee.

Would it be worth our while getting this done anyhow?
 
Yes I think so, if the specialist can give some kind of written warranty as to the the performance of the materials and what you can expect to achieve from their use. €350 sounds kind of cheap for a service like this with a meaningful gurantee.
 
A gentleman from a reputable damp-proofing outfit in Crumlin came out and quoted us €4,000 for them to strip back the walls and inject the DPC.

When he heard that the builder was stripping back the walls to the masonry anyhow, he said that his guys could come round and just do the injection for €350+VAT.

The space affected is around 20 m2.

It does sound very reasonable, but they are (I think) reputable, and he did offer a 20-year guarantee. So I think we should certainly go for it...

By the way - any thoughts about our builder's suggestion of the uPVC layer? It sounds a little crude to me. And perhaps superfluous if we have the DPC injected? It may even cause extra problems if it stops the wall 'breathing'...
 
Yeah, you're right there. Don't do it - fix the cause instead. You've got good advice so far....
 

OK based on the above, €350 sounds like a very fair price. As for the additional work by the builder- I don't really understand what he's proposing. Is he going to line the walls with a vertical vapour barrier? If so I'd be wary of this. Normal procedure in drylining (if that's what he is doing) is to fit treated battens to the existing wall, fit insulation between the battens and then overlay the lot with a plastic vapour barrier before finishing in a plasterboard lining. The golden rule (which is often broken) is to always fit the vapour barrier on the room/ warm side of the insulation. The thinking being that warm, moisture laden air will travel through the buildings fabric and condense once it meets a cold surface. You don't want this moisture vapour to travel through your dry lining to condense on the vapour barrier and soak the insulation (if fitted incorrectly).
 
Yes, I too am unclear on what the builder is proposing! So I confusing you as well... But according to my notes, what he proposes is:-
  • Strip
  • Expose wall
  • Apply sealer
  • Insulate
  • Foilback slabs
Does this sound like best practice? It seems like he's proposing to apply the vapour barrier directly to the masonry, which you advise against...

(I should probably call him again to ask him to explain it for the Nth time..!)
 
It's hard to be definitive about the solution offered, what is the existing wall construction (brick/ rubble/ cut stone/ concrete blockwork) and is the structure a protected one? How old is this building? Sealing the inside of the wall will prevent the wall from "breathing" and this is contrary to best practice in terms of conservation. Old buildings were designed to "breathe", modern materials and methods are generally not compatible with old properties unless their performance and function is understood. Foil back slabs will certainly help with condensation as the foil acts as a vapour barrier. Sorry I can't give a definitive answer here.
 
The house is made of brick and is not protected - but is just over 100 years old. I take your point about the importance of the house being able to 'breathe' - and I don't think that the builder is really so worried about this. That said, both a DPC and a vapour barrier might be overkill, or it might be just what we need. The best thing for me to do might be to go back to the surveyor and ask for his advice! Thanks for your advice.
 
simp said:
he did offer a 20-year guarantee.
Click to expand...

I always feel these guarantee's aren't worth the paper they are written on.

Does he have an insurance policy or bond in place to cover the recurrance of problem 19 years later! At this stage the company could have ceased trading, or gone bankrupt, the trader could be deceased.

I always take these guarantees with a pinch of salt and consider the contractor on his merits. IMHO i would want to see references from satisified customers.
 

Agreed, most guarantees and warranties are worthless unless backed by an insurance policy. In the case of the major flat roof membranes a registered installer will give a guarantee based on an inspection by the manufacturer who will issue a guarantee underwritten by an insurer.
However in the case of a small job like this I'd be quite happy if the product was an established one, applied by trained personnel etc. Afterall what plumber/ plasterer/ kitchen fitter/ tiler etc guarantees their work? No guarantee underwritten by insurance in most instances anyway. Talk to your surveyor- afterall that's what he's paid for. The application of a DPC where none previously existed (or where it has failed) is certainly a desirable course of action. Drylining with insulation and an appropriate vapour barrier is also acceptable but coating the inside of the wall with a barrier of some sort is not conventional practice- unless your builder is using a "platon" membrane- but that's another story
 
Thanks for that - I'll get on to both the builder and the surveyor and try to figure out exactly what is planned...

But I'll take your tip, Carpenter, that it's the room side which should be
sealed, and not the wall-side - in the event of dry-lining.

And, of course, NiallA, I take a 20-year guarantee with a large pinch of hygroscopic salts - but it's at least reassuring to be offered one...
 
Hi all,

I am currently self building my own house, nearly at the final stage!!
Early in the build I was informed by me stonemason that my bloklayers did not put a dpc in the house. There is a radon barrier in place but no dpc above ground level (150mm above ground level). I asked my engineer about this and he said it would be okay as the radon barrier acts a dpc, and just to make sure to put my path level below radon level. He also said that putting a dpc in place is just like wearing two c*ndoms! You are being extra safe!! Has anyone got any thoughts on this? I am worried about rising damp in the future.....

Thanks,
 
The vapour barrier method is a cowboy measure, even battening out a wall then adding dry lining is asking for trouble on a damp wall as the mechanical fixings in the damp wall acts to draw the moisture through the barrier and into both the timber and plasterboard resulting over time in unsightly growths of mould.....usually long after the cowboys have ridden into the sunset. P.P.C injection is an excellent method of eradicating rising damp and would advise you had the whole propert injted in one go to save any future problems.
 
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