Insulating Solid walls

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John Rumm wrote:

why did you analyse these mortars?
NT
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John Rumm wrote:

unless I'm mistaken thats normally due to mortar failure over a century or so. Repointing only usually replaces the outer layer. I'm not convinced it means the original mortar was almost all sand.

... and an unstable wall that goes very wrong very quickly.
NT
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snipped-for-privacy@care2.com wrote:

bear in mind that wall stability was a perennial probem with lime built walls. The lime was so slow to set that building progress was hindered by poor wall stability due to wet unset mortar. Saving a few pennies on lime would make the situation much worse, it just wasnt worth it. In fact interior plaster was often overly fat on lime, economising on lime just wasnt usual practice.
NT
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This Victorian pile is built of pretty porous London stocks and lime mortar - and has no damp proof course. When I bought it many years ago the BS insisted on a woodwork and damp warrenty - so I got quotes from several firms. All but one wanted to install a chemical damp course and re-plaster the external walls up to a height of 1 meter or so in a waterproof render - which would have meant removing the beautiful 14" skirting boards, and they would never have gone back correctly. The decoration in the house was all old, and wallpaper everywhere. Non of which was showing any damp - or loose. And I bought the house in the early spring after a long wet winter. No central heating in the house either. So I concluded if it had survived ok without a damp course for the best part of 100 years, why did it suddenly need it?
The reason there was no damp showing was simple. The suspended wood floor was some three courses above ground level, and there was the further 3 courses or so not plastered because of the skirting. Good air circulation in the cellar too. So any water penetration to the bricks simply dried out afterwards. If you add a waterproof render to the inside of the wall as was the practice then, the bricks can't dry out so easily.
There were a couple of minor wet rot problems where joists went into the walls sat on wood plates which were easily fixed.
--
*Happiness is seeing your mother-in-law on a milk carton

Dave Plowman snipped-for-privacy@davenoise.co.uk London SW
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Rob coughed up some electrons that declared:

What are the other 350 credits about then?
I dread the response...
When my Mum did her diploma in catering management at Battersea Poly, they had the students undertake every job themselves that they might be expected to manage others doing in the future, eg cleaning the loos.
One of the students discovered the hard way that acidic cleaners and marble tiles don't go well togther.
By strange coincidence, Battersea Poly closed and re-opened as Surrey University, and I worked for a while in what was the same department by a slightly different name (one or two of the Battersea people were still around).
Nothing like that now. They still get to do actual cooking and more "restauranty" things, but no cleaning the bogs or mundane stuff that I'm aware of.

I've seen far too many fraction of a million projects with a bunch of admin idiots running the show who won't listen to the people who have to actually make it work. Usually ends up with the customer side tech folk dealing directly with the contractors (who also want to leave something that works) on the quiet to sort out various lack of thought and outright lunacy.
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Tim S wrote:

:-) - policy, strategy, design, finance, management, development, bit of economics/politics/sociology (30-odd credits), dissertation (now called a project, 40 credits), research methods, marketing, professional practice, with a year placement. In fairness it's preparation for a job that's always had an identity problem, swinging between social worker and property manager. At the moment it's more a regulated portfolio manager type of course. But it is one of the few courses that does actually lead to a decent job.

Quite right.

Social housing (20% of all UK housing, about 5 million homes) has suffered some gross mismanagement. Ironically* (well, not ironically in my view) most has happened in the past 25 years with the introduction of managerialism and market pressures. Created a lot of jobs though ;-)
Rob
*I gather quite a few on this NG are believers of market over state.
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On 2 May, 08:58, snipped-for-privacy@care2.com wrote:

Dear Meow2
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
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snipped-for-privacy@atics.co.uk wrote:

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.
NT
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snipped-for-privacy@care2.com wrote:

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.

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.

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The Natural Philosopher wrote:

tell that to a tree.
Whether it's a problem in brick walls is of course another question...
Andy
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Andy Champ wrote:

:-) 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..
http://www.nhm.ac.uk/nature-online/life/plants-fungi/magnificent-trees/session2/index.html

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.

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The Natural Philosopher wrote:

http://www.nhm.ac.uk/nature-online/life/plants-fungi/magnificent-trees/session2/index.html
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.
NT
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snipped-for-privacy@care2.com wrote:

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The Natural Philosopher wrote:

Correct. You've offered us no experiment that demonstrates your belief in widespread rising damp, and no logical reason to believe it either. I've offered 3 experiments that cast great doubt on it, and elementary logic makes it clear that there is more than one cause of damp at skirting board level. Bring us some facts you can substantiate.
NT
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pssst "transpiration" ....
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jim wrote:

Your walls are transpiring? I've heard of green buildings, but that's ridiculous!
Actually it's scary reading NP's very good article. Not only does it contain things I'd forgotten, it also has things in that explain features of the wood that were "just there" when I last studied it...
Andy
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for others "at the back" my answer was to the following ;-)

jim
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That's what happened at my house, so I've dug a trench around it and am scraping the crud away and it's drying out, it's nicely situatied on a local rise, water drains away in all directions so i dont need any damp course in this particular case.
But will put some DPCV plastic under the new floorbaord joists
[g]
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george (dicegeorge) wrote:

Which will then rot the joists :-)
Sorry, only kidding.
For sure ther are more ways of tacking damp - even rising damp - than a DPC, but its simple cheap and very very effective, which is why its used.

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what?
I have been meaning to ask what to put between the joists and the small supporting walls under them- slate or some kind of plastic?
[g]
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