Does anyone know if silicone injection damp-proofing is effective? I have what appears to be rising damp along the two walls of a room in my 1900-built house. (The damp can be detected up to about 4 feet above the floor). I suppose it could also be damp penetrating through from the outside skin of the cavity wall, if the cavity has some debris in it. Due to the 104-yr old age of the house, I guess it was built with a slate damp-prroof course if anything. Would silicone injection likely cure it - and if so, how long for?
If it is effective, can anyone ecommend a cost-effective place to hire the gear from and where to buy the liquid? Any tips on actual application?
have a look at the brick pattern of the walls, if it's the same as a modern house with bricks overlapping by fifty percent then it's likely it has a cavity, if as with mine it has one long edge of a brick followed by the short end of a brick (flemish bond) or layers of ends of brick over sides of brick( English bond) then it's likely you do not have a cavity. Also if there is no cavity then the wall will only be nine-ish inches thick whereas a cavity wall will be at least 11 inches
In my limited experience of *Real* serious rising damp, ( are you completely sure you do have *rising* damp?) silicone injection is a complete waste of time and money. Internally you will still need to remove all plaster/render upto 1.2 Mt and apply a water/salt proof render coat to the walls before you can re-plaster. By doing this you stand a far chance of pushing the damp somewhere else FWIW the fluid and the injection equipment can be hired from.
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A cheaper and more effective method however is this
It is probably effective in the sense that it will introduce a damp proof layer in a wall. However whether that will cure your problem is a very different question. It would depend on why it is damp.
Detected how? Have you drilled samples and tested for moisture content in the removed material, or just used an electrical resistance tester?
The most common causes are "bridging" (i.e. soil/path level above DPC), broken down pipes/gutters etc. Lack of heating and ventilation (blocked air bricks, fitting DG windows and hence eliminating natural ventilation) inside the building and hence condensation.
It could well be a solid wall at that age. A slate layer would be a typical DPC for that age. Assuming there are not extensive cracks in the wall, how exactly does a bit of slate "fail". Does it cease to be slate? There is a possibility (although unlikely) that no DPC was ever installed, in which case adding one may help.
Can't help you there - although I am sure the kit can be hired, and it will presumably work out much cheaper than getting a damp proofing company in to do the work.
In other words, the wall consists totally of stretcher bricks with no headers? Ie all the bricks are lengthwise with none end on?
All the true cavity walls I've ever seen have a damp proof course. If you can't see it for some reason to be sure, then that needs to be addressed first.
On its own, a silicone damp course won't cure the problem. It has to be combined with a waterproof re-plastering of the inside. Which beggars the question as to whether the silicone does anything worthwhile at all.
I would caution the OP about this path of action. 1900 houses handle damp entirely differently from modern buildings, and dpc injection can result in the fabric of the building beginning to disintegrate near ground level. It is not suitable for Victorian buildings.
Nor is it effective in such buildings, it hinders the damp control system more than it helps it. It seems to me you need to understand how your building deals with damp, and what things you can rectify. To speak with the experts, I'd suggest:
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other general interest, most Vic houses had no dpc of any kind, and there are indeed 9" thick cavity walls, its called ratbond. Vics with dpc usually used slate as the dpc material, and slate dpcs often become ineffective due to them being bridged on the outside with mortar. Of the few slate dpcs I've seen at least half were bridged by inappropriate repointing technique. However if this has been done, one should be wary of breaking the mortar off, since cement in sound condition is a lot stronger than slate.
The strict answer to your questions is Yes. But it won't do it by itself. An injection damp proof course is part of a system with the other part being the re-plastering. If you need the injection, you need the replastering!
You have to ask yourself whether you have 'rising damp' in the first place and a good place to start is to look at your 104 year old house, its 104 year old skirting boards and its 5?/6? year old decorations. If these are ok then, even if you do have rising damp, it isn't doing much damage is it? Just because it's there as a phenomenon doesn't mean to say you have to half wreck your house to clear it. If it's not doing any harm, leave it be and let evaporation take care of it.
By far the commonest damp problem experienced in the UK is caused by condensation. Show me an old property that has PVCu windows, a gas fire and as many other ways to block up ventilation as modern developments can produce and I'll almost certainly be able to show you a house that's suffering from condensation problems. Especially on North and East facing outside walls. It also mimics very well the appearance of rising damp, much to the confusion of building society surveyors whose sloping shoulders then contribute to the joy of the damp proofing industry! (But that's another story).
Having said that, if you really *do* have a visible tide mark at a height of one metre or so and your wall paper is peeling then it's time to look into it further and to consider an injection dpc and replastering. (Why hasn't anyone else who's lived there before you been troubled)?
If you've been using a moisture meter then check your skirting boards, top and bottom. If they have a moisture content of less than 18% (20% at a push), then the walls they're in contact with haven't got enough moisture in them to cause you any problems, at least as far as rotting skirtings are concerned. However, if you have a timber suspended floor and the joist ends are bedded in the wall, investigate a little further to see if they're at risk of rot. (Your moisture meter is calibrated to read moisture content in timber incidentally, not in other materials). Twenty percent MC or above and you need to take action - even though they may have survived intact for 104 years!
Don't bother with drilling holes and taking mortar/brick samples because, unless you have a carbide meter (Speedy Meter) PLUS gravimetric testing facilities, this isn't going to help you at all. Carbide meters only give the total moisture content, and the total moisture content is always the sum of ground/penetrating (free) water plus hygroscopic (aborbed from the air) moisture. You need very careful laboratory analysis to define the ratios. The total moisture content can just frighten you into the wrong course of action - eg., an unnecessary injection dpc. (Remember that when the man with the Speedy meter comes to call)!
If it's a real problem for you I would suggest you contact an independent Remedial Treatments Surveyor (if you can find one) and pay the hundred pounds or so he'll charge you in survey fees. It'll probably save you a fortune in the long run.
Something else to remember when thinking about adding impermeable layers / coatings / membranes to walls etc, it that much of the flow of water through a wall is from the inside to the outside. So sealing it can make damp worse.
I used a resistance tester. Also, the wall was plastered with some very moisture-absorbent plaster. you could actually see the damp in the unpainted plaster (as a darker area) after I stripped the walpaper off. You could feel it by touching it too.
Its a cavity wall. I've eplaced bricks in the outer skin, etc.
It's really hard to ascertain if a DPC is even present because the outside of the house had ben rendered with some strong mortar.
I reckon it might be worth a try. The re-plastering of the interior is the biggest nightmae though. I just want to sell the house. I'm now thinking it might be better to sell the house at an appropriate price and let the buyer worry about it.
The decor, the plaster and the skirtingboards have all ben replaced at some point in the last 25 years. The damp is quite bad. And it'd not condensation. It's definitely coming out of the wall. (the first four feet off the floor).
That has been my approach for the past 13 years, but even after painting the walls with waterproof damp-block paint, it's quite bad. I reckon it would scare off many buyers.
Who can say? Maybe they were troubled but couldn;t afford to deal with it.
They are. I had to repair some of the joists when I moved in, 12 years ago.
It IS effective IF the problem is rising damp. The comparisons between walls that had been injected and those that had not in my old house was startling.
Yes, that's the popular conclusion but perhaps it misses the point. An injection dpc is a system which consists of two parts. The purpose of the injection is to control the damp and restrict it as far as possible. It's highly unlikely, even in ideal circumstances that it will completely stop the damp but, in conjunction with replastering, it will control the problem so that it becomes acceptable. Merely re-plastering a wall could have unforseen consequences such as (if there really is rising damp) encouraging it to rise even higher to the point where it's above the level of the new plaster. This phenomenon is quite distinctive and is an indication that an injection dpc has actually failed.
The re-plastering not only stops any residual damp from migrating to the surface but it has another, and perhaps more important purpose which is to remove chlorides and nitrates which will have migrated to the surface of the old plaster. If they were left there then the wall would be forever hygroscopic and no matter what you did with injections, or physical dpc's for that matter, the wall would always be damp.
The presence, or lack of, salts in a wall is sure indication of whether there's ground water (rising or penetrating) in it but unfortunately it's a diagnostic method which is eschewed by the dpc industry. It's much easier to stick a moisture meter into the wall, listen to it buzz and flash red and con the poor househoder into paying for an injection dpc to cure the condensation caused by the double glazing which was sold to them on the basis that it would cut draughts and create a pleasant atmosphere. It all brings on five o'clock wouldn't you say?
What is your proof for this statement? If the house is built of brick or stone then why should a silicone injection cause it to deteriorate any more than a brick or stone which is in a house built in the 30's?
An excellent site but there are other opinions.
Sorry, this doesn't make sense. A mortar joint will cause only a minimal bridge and will not normally contribute in any marked degree to the passage of rising damp. It will to a degree but only marginally, especially if it's cement based (as opposed to lime). That's why a re-plastering base coat should be sand/cement!
Also, I can't see the connection between breaking off the mortar and the condition of the slate. Are you suggesting it's somehow become a structural item? I'm not being facetious,I'm genuinely puzzled.
Ratbond is a cheap way to build walls quickly and, according to BS6576, is not to be injected under any circumstances. But this is because of its construction, not its content!
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