Dear Dave It is not clear to me for certain, but it appears that you are disagreeing with the assertion that rising damp exists and that you think that no treatment is needed and are citing Geoff Howell as an appropriately qualified, experienced source of unbiased opinon based on good science and statistics. If so, I beg to differ. I do not share Geoff Howell's opinion on rising damp and what it appears that he is claiming. Where is he is right is that many, if not most, dpcs recommended to be put in by unqualifired firms are not needed. Where I think he is wrong and biased is his apparent assertion that rising damp does not exist. He managed to get a substantial grant to research RD at, I think, the University of the South Bank (the old building Poly) which was in many parts a repeat of the work done decades before by the BRE to which anonther post has referred. I will reply to that post as to why I think the BRE work did not work but that is only my opinion! I have surveyed houses for considerably longer than Geoff and have more academic qualifications in more fields - general biochemistry as first degree and specific timber biodegradation as PhD and an Masters in timber engineering. I also have taken and passed with credit in all three modules the CSRT. Geoff has as far as I know a BSc and I understand he is a qualified bricklayer as well but may be wrong. What I do know is that none of the colleagues I have worked with in universities or in the BWPDA or BRE agreee with his theses and I have yet to see a learned paper from a peer reveiewed scientific journal with evidence to support his views. I have seen rising damp in many hundreds of houses
If I were to guess how many houses are needing treatment versus the ones actually treated I would think that it is a minority as Geoff is quite right that lots and lots of treatment is done which is quite unnecessary
I am familiar with this work and some of the people that did it. I put forward the possible answer as to why it was the case
RD is actually hygrocopic salt deposition in plaster and mortar. It happens over decades I happens mainly in old houses for that reason Most houses post 1886 or thereabouts had to have a dpc Put a pile of bricks in WATER and water will be conducted up not ground salts even if salts are in the water there is a huge difference in the environment of a lab (trying to accellerate a process that normally takes decades) and the real thing Walls have an environment which is opent to the air and sun and are based on ground which is a complex material
The BRE experiments simply did not replicate what happens natrurally over decades
The argument of lime v cement mortar may well be not relevant as observations that it occures onoly in lime mortar buildings could be related to the dpc regulation of the 1880s and the introduction of cement a couple of decades later who knows? Chris
Dear Tim I suspect we have corresponded before. You have a namesake that is an engineer that used to work with Stephen . I graduated from Trinity in '69 and regularly go back for DUBC occassions still pulling an oar and keeping in touch! Happy to advise you pro bono on any such property and have considerable expertise (that is practical experience) of internal insulation. Is the house in ~Dublin or beyond the pale (as one might say in the old days) Wicklow is great and good for a commute! let me know off line and I can help Chris
interesting, as a lot of them don't. It was quite normal for houses not to meet local regulations in the 1800s.
good point. Tap water contains salts but less salts make it a slower process.
... over decades, no. But there are (unintentional) experiments that have. I must dig up the details when I have time, but to summarise in some countries masonry houses have been built in rivers, with the ground floor above the water line, and centuries later no rising damp.
You make some good points.
From a practical pov, I think that damp at the base of walls is much more often not RD than is. Penetrating damp and condensation, plus salting due to ground splash or poor use. And piling up rubbish by the wall doesnt help.
The downside is that any water that gets trapped behind the celotex has only one way to go. Inside the house. Makes the injection even more critical. That means you HAVE to create a really good water barrier outside the celotex..
Conversely you have a lot of thermal mass inside the insulation which is excellent in summer, as it will moderate the hottest part of the day down. Conversely, in winter, it ,means you need to run heating earlier to get up to temperature (if timing).
With a timer cald outside though, its not a bad way to go. Replace vertical battens by maybe 2x2 pressure treated, celotex between, and foil tape the lot before re-boarding.
Pay attention to window and door openings: I'd be inclined to use expanding foam to seal any gaps between celotex and the masonry, and board over afterwards
The limit of capillary action is inches, not feet. My house suffered very badly from it, but it was limited to at best 12" above the local 'water table' - that was with extremely porous brick and probably lime mortar.
If you have damn around skirting height, rotten floor joists and blowing plaster an inch or two above that, its almost certainly rising damp: Above that its almost certainly not.
Well at least you agree that water penetrates brickwork. Injection stops that dead. The only issue is whether its capable of rising from where its in contact with it. My experience says yes, although not very high. But high enough to be an issue when floor levels are only 4-6" above very wet soil indeed. Go up a foot or so,and you are mostly out of danger. However that means a definite 'step up' into the building.
I don't claim any particular expertise here, but a vapour barrier is used to prevent warm moist indoor air migrating to a cold surface where condensation will form. If you have external insulation and it is moisture-proof such as foiled celotex/kingspan, then there isn't going to be any place where condensation can form. However, in practice, it's unlikely that the celotex/kingspan is going to be your only insulation layer. For example, if your inner skin is thermal blocks, then they will also contribute to the insulation, and the junction between the block and Celotex will be colder than indoors, and there's scope for condensation there. My guess is that is not likely to be enough colder to be below the dew point and plastered walls won't be sufficiently moisture permiable, but I would seek some expert advice here, and there are probably applicable building regs.
The other thing is that thermal blocks don't have a lot of thermal mass anyway (compared with bricks or clinker/breeze blocks). I was thinking rather more of victorian houses with brick walls when I made the comment about external insulation. It's worth thinking about for a newbuild, and I share your dislike of drylined walls. If you can get non-thermal blocks (with higher thermal mass) cheaper, possibly in exchange for another 25mm of celotex, that might be a good idea.
Dear Chris, I note from your company's website,
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, that you are mainly concerned with timber decay, wet and dry rot. You give extensive data and information on timber problems and treatments and only THREE SENTENCES regarding 'rising damp'. One sentence tells us to see a link all about fungal decay in wood. Very helpful. The other two sentences tell us what rising damp is, and what you will do about it.
As you give so much technical detail about timber problems why don't you do the same for 'rising damp'? Why don't you show how you prove that the dampness is coming from the ground ? Why don't you describe the test gear/equipment you use ? Where are the details about various bricks, mortars, cements etc.? Where are the graphs showing how damp rises up walls ? I'm sure clients would be reassured and impressed to see similar details as you provide for timber treatments.
I do hope you drilled out a sample of brick and did a chemical analysis of the water/salt content and not just poke an electrical resistance meter at the walls of these ' many hundreds of houses '.
As you are based in London you must have heard about Lewisham Council offering a cash prize a few years ago to anyone who could demonstrate a case of rising damp to them. I believe the man involved at the time was Mike Parrett. I hope you claimed your prize.
Oh, yes. If you are plasterboard lining a modern block structure, simply use foil backed, and accept the fact it screws the phones and radios..but the celotex will do that anyway! You shouldn't have any problems anyway though if celotexing outside..IF you make the celotex airtight to the block, the 'cold' surface is the outer skin of the celotex. But its already got its own vapour barrier.
Should work. Im a bit leery about battening over and through the celotex..but there is no reason it shouldnt work. I would be more inclined to use exterior timber screwed to the block, mount a slab against it, and then another stud and so on. Then batten over that nailing to the stud. Breathable paper in useful to stop rain driving in past the weatherboarding and getting to the battens, or battens and studs.
Definitely last bit of woodwork should be vertical with an airgap to the celotex to allow air behind the boarding. That should vent near the DPC and at eave level.
I must say if you atrer wood cladding ousisde, i wonder why you ise block at all..use a timber frame, plate in ply, then paper and battens and weatherboard, and stick the celottex inside between the studs..
Thats what I have. More or less. Cavity brick up to about a foot off the ground, with a DPC.batts inside, then sole plates and studowork above. Outside is rendered over wire rather than boarderd., otherwise its the same.
Not a problem really. Build a softwood treated frame outside the blockwork there.
Piece of piss to screw that to the block and attach windows to it. You can run the boarding over the top of that, and if the window is left a bit proud, up to the edge of the window. I.e. dont fit the windows till its all boarded up. Then a bit of mastic will seal 'er up nice.
Its a bit of a cold bridge, but life is never perfect..so is the window frame anyway!
Then line the alcove with plasterboard. and a nice window board. And maybe tidy up outside with a drip board and some lead run under the board above and over the drip board top.
:-) Actually its NOT capillary action in a tree. Its summat else. whose name I forget.
Ok its is a sort ocapillary action, but not as we normally understand it..
Its not surface tension per se..
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You can see it in an un-DPC'ed wall..it comes up from the ground a few inches..maybe a foot.at most. It doesn't 'cut off' so much as evaparate out faster than it gets sucked up.
This is where meow gets it muddled, and starts talking about water proofing making things damp. Of course, if you stop it evaporating OUT it evaporates IN as it were, and you get soggy plaster.
ergo the typical problem when a crumbling brick plinth is rendered over, leading to a damp problem inside.., the answer is subfloor injection, to stop it rising.
My old house had that, both, and it all worked BUT they couldn't inject the fireplaces/cho=mneys or certain walls that were unreachable and below floor level in teh middle of the house These suffered massive damp and rotted the floorbards and led to plaster coming off the brickwork.
The fact that there were underfloor vents just above concret pathways meant not that the soil under the house was dry, but that water poured in and formed a lake, in which these internal walls stood!
about 4" up from the lake teh timbers and floorboards rested in these. They were literally like wet sponges. Being inside the house, there was no other way that water COULD be getting in except from below.
Two back to back fiers/chimneys and a bread oven all flued up a triple stack was the other area with major problems Both had been equipped with Victorian coal excrescences, and the walls then plastered up to those over the original brick. The plaster lasted bit the paint was peeling off - I made it good every few months.
If you didn't keep the rooms well heated they stunk of mould. You could see it all over the bottom 4-5 " of that wall area, but no higher. Since the whole effigy was about 4 foot thick I didn't see any possibility of injecting that either.
but that has nothing to do with reality at all. It is singularly ineffective, the fluid merely takes the paths of least resistance.
What does make a difference for a while is replacement of the plaster, removing salt laden and putting on fresh. This is why there were no complaints with the company that injected water - they replastered.
if only. a) injection doesnt stop water rising in the wall b) the problem usually isnt water rising
other than condensation
Again you tell us that if damp is only near the floor it must be coming upward. Its a non-sequitor. Colder near the floor means thats where condensation happens first.
How very interstingly *direct* your questions are... It would appear I may have stumbled unwittingly on a raw nerve...
Here are the answers to your questions
Dear Chris, I note from your company's website,
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, that you are mainly concerned with timber decay, wet and dry rot. You give extensive data and information on timber problems and treatments and only THREE SENTENCES regarding 'rising damp'. One sentence tells us to see a link all about fungal decay in wood. Very helpful. The other two sentences tell us what rising damp is, and what you will do about it.
As you give so much technical detail about timber problems why don't you do the same for 'rising damp'? Answer: Because after we did our first two rising damp jobs in 1978/9 as contractor, it became clear to me that there was no money in being a damp-proofing contractor if you were to provide a completely honest unbiased survey service as the cost of a decent survey was about the same as the cost of treatment and that was not fair on our clients. We simply stopped being a damp-proof installer.
Why don't you show how you prove that the dampness is coming from the ground ? Answer :Why shoudl we? I / We have not proved the dampness came out of the ground. We have made no such claim. I have merely read the literature extenisvely, talked to the chaps at BRE or ex-BRE who are recognised as being scientists and have worked in the field and, more importantly, kept a keen eye out on the several thousand houses I have surveyed from Craigievar (sp?) caslte in Aberdeen to Osborne House's Swiss Cottage in the Isle of Wight. I have observed not dampness coming "out of the ground" but dampness coming out of a wall plaster or in mortar as a result of hygroscopic salt contamination. The presence and quantity of such salts are very easiy "proven" by well- established tests that one does for "O" level or GCSE - it does not take a degree to identify them and prove presence. I have done such tests and proved the presence of such salts
Why don't you describe the test gear/equipment you use ? Answer: Because I do not need to for sales purposes on our website. Why would the client be interested in our Speed meter, our Sovereing capacitance meters (3No) and various resistance meters? Why would he/ she be interested in paying a four figure sum of a proper BRE 245 test?
Where are the details about various bricks, mortars, cements etc.? Answer: What aobut them? We are providing a service rather than a Wiki
- we provide information on or service. If however, a client makes contact they get a full hard copy of what literature we consider is suitable for their enquiry. Our call - our choice.
Where are the graphs showing how damp rises up walls ? Answer: Why should we show such graphs? Such data are in the public domain.
I'm sure clients would be reassured and impressed to see similar details as you provide for timber treatments. Answer: As we do not offer and have not offered a rising damp
*treatment* service as contractors since at least 1980, we see no reason so to do. We do, however, offer an expert opinon service and have, indeed, done the BRE test for hygrosopic salts and free water (Digest 245) using samples from drillings and equilibrating at RH 85% and they oven- dry weight
I do hope you drilled out a sample of brick and did a chemical analysis of the water/salt content and not just poke an electrical resistance meter at the walls of these ' many hundreds of houses '.
Emphatically not - why should I waste the client's money on proving something that any surveyor with experience and a brain sufficiently open to interpret what he sees and the results of meter assessments in the *distribution* of water in a wall combined with where necessary simple salt tests? Only where there is litigation is is necessary to use a ~Speedy meter as that is proof rather than opinion
As you are based in London you must have heard about Lewisham Council offering a cash prize a few years ago to anyone who could demonstrate a case of rising damp to them. I believe the man involved at the time was Mike Parrett. I am well aware of this but - as I say - we do not act as contractors and I will add that we stopped doing "Council" work pretty early on as they were such slow payers and tried to impose "their" rates on us. Most, when they heard that we charged for surveys, were simply not interested. It is only when they get into serious litigation problems that they tend to wake up and pay the man what he is worth.
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