Injecting a DPC

[Zebra]

I have a house some centuries old, which is 9" solid brickwork on the ground floor. Most of the builders and experts who have seen it say I really must have it injected. But I don't think so! What are peoples experiences of injecting DPCs in old houses?
The ground levels are no lower outside than inside, and on one wall the outside is 300mm higher (I am going to install a French Drain - see my other post on the subject).
So it seems that if I injected a dpc, it would have no effect on those courses below the injection anyway, so I'd still get damp low down, and on the one wall where the ground is higher outside, the injection would have to be above external ground level, so what would be the point!
I need back-up please!!!
Many thanks all..

 

[Flyfisher]

I seem to have mislaid my copy of "The Rising Damp Myth" (http://www.askjeff.co.uk/rising_damp.html) so I can't give more precise details but I recall a fairly detailed description of the pitfalls of injected DPCs - quite apart from the whole controversy of whether they are needed or effective in the first place.

Basically, the criticism was based on the speed and or pressure at which such works are typically carried out, making it effectively impossible for the injected waterproofing agent to adequately percolate through the bricks and completely fill the spaces between the holes drilled for the purposes of the injection, thus physically defacing the property for no effective gain.

Damp can be a contentious subject but, given the considerable sums of money usually at stake, I'd recommend as much background research as possible - including reading this book.

 

[biffvernon]

Most of the builders and experts who have seen it are wrong. Don't bother with injections.

It's funny how so many people seem to be be wrong about so many things but there it is.

 

[Matt Green]

Most of the builders and experts who have seen it say I really must have it injected.

Why? Is there evidence that a problem exists that requires solving with an injected DPC? If so can it be definitely traced to a lack of DPC?

Basically, the criticism was based on the speed and or pressure at which such works are typically carried out, making it effectively impossible for the injected waterproofing agent to adequately percolate through the bricks and completely fill the spaces between the holes drilled for the purposes of the injection, thus physically defacing the property for no effective gain.

That really outdated to be fair. Even the worst in remedial DPC companies will use silane/siloxane creams injected into mortar courses these days, less noticeable but still irreversible. The Old House Handbook (M. Suhr) is a little more up-to-date on matters.

M
-my cagey wording is deliberate. :|

 

[JoceAndChris]

Don't do it Zebra. They always try to give the hard sell for this but you're better off opening the window and going out and buying a nice antique for your lovely house!

 

[robgil]

Wont this force all the moisture out through the bricks beneath the DPC thus prematurely blowing the faces off them or rotting the mortar?

 

[Zebra]

Is there evidence that a problem exists that requires solving with an injected DPC? If so can it be definitely traced to a lack of DPC?

Quite! There was cement render on the bricks inside and out. They'd "tanked" it, basically, in the 60s. The paint on top was blistering, and there were days in the winter when you could burst a blister and water would run out of it.
However, I've taken all that cement render off, the bricks are breathing, and have dried out nicely. Clearly I won't know til next winter whether I'll have water running down the walls again, but with a French drain outside, and other measures I could take, my instinct is to keep the builders' hands off it, wait another winter and see how I go!

Most of the builders and experts who have seen it are wrong. Don't bother with injections.

Thank you, yes! A bricklayer came the other day, I thought to give me a hand with lime repointing, and he said "That wants tanking, that does" Aaaaaaaaauuurgh!

Wont this force all the moisture out through the bricks beneath the DPC thus prematurely blowing the faces off them or rotting the mortar?

Well quite! It will make the courses beneath the DPC wetter! Does mortar rot? Come to think of it, there were courses below external ground level where the mortar courses were full of mud....

 

[CatherineB]

Zebra, while what I know of damp outside of this forum could be writ large on a postage stamp, I would agree with your instinct. You have already taken, and are proposing to take further, very sensible steps to reduce the damp problem in the cellar. I would see what effect those steps bring before taking the "experts'" advice of injecting a DPC.

 

[robgil]

Well quite! It will make the courses beneath the DPC wetter! Does mortar rot? Come to think of it, there were courses below external ground level where the mortar courses were full of mud....

Your bricks are softer than modern ones so might not like being saturated more than they need to be.I am no expert but any lime mortar I've found here that had been damp for long periods has turned to dust.

 

[Merlin]

Having spent the last few weekends digging out the foundations of the brick outbuildings, I was surprised at how well the lime mortar and bricks had survived 115 years underground. The mortar was still solid, and binding to the bricks. The bricks were in superb condition and still entirely intact.

I must admit to wishing they were in worse condition, as they would have been much easier to get out of the ground.

 

[AMc]

FWIW the lime mortar that I've seen seriously deteriorated here has been both wet AND exposed - I presume that's the interaction of temperature change with the moisture.
When we dug the test pits to show building control the footings the mortar was fine despite being 4 feet below the surface.

 

[MatthewC]

However, I've taken all that cement render off, the bricks are breathing, and have dried out nicely. Clearly I won't know til next winter whether I'll have water running down the walls again, but with a French drain outside, and other measures I could take, my instinct is to keep the builders' hands off it, wait another winter and see how I go!

Absolutely, trust your instinct. Don't rush it, let it dry and see what it's like after your improvements.

 

[Lime]

However, I've taken all that cement render off, the bricks are breathing, and have dried out nicely. Clearly I won't know til next winter whether I'll have water running down the walls again, but with a French drain outside, and other measures I could take, my instinct is to keep the builders' hands off it, wait another winter and see how I go!

Absolutely, trust your instinct. Don't rush it, let it dry and see what it's like after your improvements.

Precisely.

 

[meljones35]

Our very sensible structural engineer, who is generally against DPCs in old buildings did point out that, were you to want to sell it, some mortgage companies would not lend on it without a DPC. Is this correct?

 

[MdB]

Our very sensible structural engineer, who is generally against DPCs in old buildings did point out that, were you to want to sell it, some mortgage companies would not lend on it without a DPC. Is this correct?

This can be an issue, however one of the experts here did post a rather well worded letter that worked on a number of occasions in getting around this problem. Hopefully somebody can post a link to the letter as I can't find it quickly.

http://www.periodproperty.co.uk/forum/viewtopic.php?f=1&t=10798&p=131001&hilit=dpc+letter#p131001

 

[Penners]

Our very sensible structural engineer, who is generally against DPCs in old buildings did point out that, were you to want to sell it, some mortgage companies would not lend on it without a DPC. Is this correct?

In such cases, I would get the sensible structural engineer to put that advice in writing, then show it to the mortgage company.

 

[philpjuk100]

Injected dpc`s do seem to have some effect,our property was given an injected dpc in 80s when it was "restored" together with concrete floors,gypsum plaster and repointing with cement mortar.The inglenook in the kitchen exibited a small amount of damp,up a couple of bricks from the floor(above the dpc which seems to have failed),we could put up with this until we could afford limecrete/underfoor heating and lime plastering.BUT this spring my neighbour whose property joins on to ours at the chimney had the builders in who injected his walls,the damp in my ingelnook has now reached shoulder height,the plaster now has bubbles and salt showing and sounds loose so some urgent attention is now required,I think that I will try removing the plaster let it dry out and replacing in lime as I cannot afford the floor/heating yet.My neighbour when I mentioned it to him said he would send his builders around but I told him that I would sort it myself.Take care,do it correctly. phil.

 

[AMc]

Our very sensible structural engineer, who is generally against DPCs in old buildings did point out that, were you to want to sell it, some mortgage companies would not lend on it without a DPC. Is this correct?

I'm not sure that's always true. My brother had an Edwardian basement flat which showed signs of damp on the valuation (with the magic meter which you can't trust) - as I now know from the cement render - the building society imposed a retention of £1000 on the mortgage. Basically any sum he tried to borrow they reduced by £1000 until he could show an insurance backed guaranty for an injected DPC. It didn't work of course but he was forced to do the work within 6 months of completing the purchase.

When we sold our last house their survey showed evidence of damp - which in retrospect I knew about following a fault on the phone socket in the wall. I now realise was a cement splash back that the previous owner had just fitted ajoining the crazy paving patio in front of the wall.
We offered £500 in respect of the works which the buyer agreed. I don't know if they had the work done but after a year our solicitor sent us a cheque for that amount which she'd retained waiting for evidence of the work which never arrived.

I think that if your house shows evidence of damp or moisture using the wood moisture meter that valuers use then you may have to argue with a lender but I think having the work done pro-actively when it is known to be of dubious benefit would be a mistake.

 

[Matt Green]

BUT this spring my neighbour whose property joins on to ours at the chimney had the builders in who injected his walls,the damp in my ingelnook has now reached shoulder height,the plaster now has bubbles and salt showing

That is not a result of the DPC, that happen due to the replastering that has gone on at the same time. Now your neighbour has new cement plaster on his walls the water in the wall has nowhere to go but through your side, raising to a point where the evaporation pull from the room and the capillary pressure in the wall are equal.

Cement plastering will prevent water evaporation and provide a water damage free decorating surface for a good few years even without an injected DPC.

 

[Zebra]

I definately do have rising damp though, because I have it on internal walls also, which used to be external walls once, and where the ground level is the same on both sides, but the wall is surrounded by a cement floor. The bottom few courses are affected.

Has anyone ever tried one of those electro-osmotic damp proof courses?