More Boring Work Stuff

Phil A · Nov 2, 2011

OK, so you all helped out fantastic on the last article I did for the website,
ta very much for that

Started writing this one when sober but then it crept into Ziggy's happy place hour so it may have gone a bit Uber.

COB CONSTRUCTION
In areas of The Country where there was little suitable building stone or where transportation of materials was a problem buildings were often constructed from a mixture of Chalk Mud and Straw. This is known as Cob.
Cob Buildings and Walls can still be found in places such as The West Country, Salisbury Plain and East Anglia.
Construction started with a Stone or Brick plinth, about a yard wide by a foot or so high. On top of which, layers of well mixed cob were built up, either by pitching it on or by compacting it between shuttering.
Layers were allowed to shrink and partially dry before the next layer was added. Lintels for Doors and Windows were added as the Walls grew.
When Wall Plate level was reached the most common roof construction was a wide Thatched Roof, to keep the rain away from the Walls.
The Cob would then be rendered in a breathable Lime Mortar and Limewashed.
The internal floor could be either Rammed Earth, Lime Ash or Quarry Tiles.
This type of construction will last for centuries as long as water does not penetrate the walls. It must not however be allowed to dry out completely, as this could result in loss of cohesion in the Cob.
The thickness of Cob walls provides excellent thermal and sound insulation, once the walls have warmed up, the thermal mass holds the heat very well. Unfortunately, thermal mass is not taken into account by the current Energy Performance Certificate, but that is another story.
COB PROBLEMS
As I said, Cob Buildings and Walls have been around for hundreds of years. Many Walls were hastily built in Hampshire to protect vegetable plots from being plundered by hungry troups returning from the Napoleonic Wars. They disembarked at Southampton and were left to fend for themselves. These walls are typically capped with Double Roman Clay Tiles.
As long as they had "A good hat and dry feet" they performed well. Some damage has been caused by Rodents digging into the walls, you often find broken glass in the first layer to prevent this.
After a wet winter followed by a deep frost Cob will often suffer surface damage. This is not a major problem if repaired sympathetically with the correct materials.
Problems arise when patches are repaired with cement render. This is totally inappropriate with Cob. It will not adhere in the long term, it is too heavy and brittle compared to the substrate, but in the short term it will crack and allow water penetration without the ability to let the water evaporate out again.
Now a bad repair might cause some localised damage to a wall, but consider a totally inapropriate renovation of a Cob Cottage.
I mentioned the rammed earth floor earlier, that is important. The floor area needs to be breathable, both inside and out. Its highly unlikely that there will be a damp proof course in the masonry plinth. So any groundwater needs to evaporate before it starts getting into the plinth.
If a waterproofed concrete floor with a damp proof membrane is put into a Cob Cottage then this will force ground moisture to "wick" up through the lime mortar bedding of the plinth. This might not be a problem if it doesn't rise as far as the Cob itself, but the next thing that could happen is that soluble salts will start to come through the lime plaster on the inside of the house. There will be wetting and drying zones as the heating is turned on and off in the house causing plaster failure.
The modern aproach would be to strip the bottom metre of internal plaster and "tank" the walls (applying waterproof bitumen before re plastering with a modern gypsum plaster).
This is very bad for Cob buildings.
If this had been done then the problem would manifest itself on the outside of the building. The damp has to come out somewhere, so the same process would lead to low level failure of the lime render this time with frost action being a factor as well as salt crystalisation.
Now if a contractor not familiar with Cob buildings were to be asked to remedy this situation he would more than likely suggest a waterproofed cement render and an injected chemical damp proof course.
This would be the final kiss of death to a cob building.
The Silcone damp proofing injection might work on a bone dry plinth, but not on one where the masonry and bedding mortar are already saturated with water, silicone will not push the water out of the masonry.
The waterproof cement render will only serve to keep the water in the Cob wall and when it cracks due to its inability to flex with the natural movement of the building this will compound the problem, letting water into the structure that cannot easily escape.
The result will be the Cob will become so saturated that it will turn to liquid, resulting in total structural failure.
The weight of the roof will crush the entire building to ground level,most likely killing all the occupants.
Still, a general builder is cheaper than a specialist.
Your Choice.
Click to expand...

Hope thats no too tedious. Managed to get that together between finishing the pumpkin wine(making it that is, not drinking it:DOH processing the last major batch of tomatoes, sorting the next bit of the candied apples, making a pasta, giant puffball & banananana shallot meal for the kids, sorting out a new paypal account & complaining to google ads about their terrible website and totally refinancing my accounts.

Be good to get back to work tommorow for a rest

Val.. · Nov 2, 2011

I noticed that the word inappropriate has 2 'ps' Likelihood is spelt with an 'i' not a y

Val

HYDROGEN86 · Nov 2, 2011

"Still, a general builder is cheaper than a specialist. Your Choice."
:OUCH:

Sheal · Nov 2, 2011

Another good article Ziggy. It made sense to me anyway!

Right, a couple of things.........Towards the bottom, the paragraph starts.....The silicone damp proof injection...........you missed out an I in silicone.

Also there are a lot of words starting with capital letters that needn't be!

You asked! I'll get ready to duck, when that missile heads my way!

clueless1 · Nov 2, 2011

It is very good until about two thirds of the way through, but then it starts to get a bit angry.

I know you are passionate about your work Zig, and that is good, and potential customers will want to know that too, but its best to stay objective.

HYDROGEN86 · Nov 2, 2011

Lmao that's what I felt but could not quite put my finger on it. I like the ending it reminds me of an episode of horizon

Phil A · Nov 6, 2011

Cheers all,

Advice taken and amended

Heres the live page

https://sites.google.com/site/searc...ration-or-conservation/cob-construction?pli=1

Scrungee · Nov 6, 2011

Cob Buildings and Walls can still be found in places such as The West Country, Salisbury Plain and East Anglia
Click to expand...

A form of cob buildings & walls is also to be found in Buckinghamshire, where it's called Witchert, Whitchert, Wychert and the stone plinths are called Grumplings (I worked on a project involving major reconstruction of a badly fire damaged Listed wychert cottage many years ago).

Phil A · Nov 6, 2011

Oo, I love that Scrunge. Grumplings, best word of the month so far

Chert being a type of flint, so Whitechert being a good description of a chalky flinty mix I guess, not heard that before, but never been to Buckingham that I know of...... runs away to google where it is:o

Phil A · Nov 6, 2011

Oh, I have been there, only to see Bowie in concert though.

Jack McHammocklashing · Nov 6, 2011

Paragraph COB PROBLEMS

Troups TROOPS

Jack McH

Phil A · Nov 6, 2011

Cheers Jack,

Sorted, thats why I need you guys

Axl · Nov 6, 2011

I'm getting this message from your site; "This site has insecure content".

Chrome is telling me this;

"locking Insecure Javascript
When a website is secured via HTTPS, the web site designer must also ensure that all of the scripts used by the page will be delivered in the same secure manner as the main page itself. The same requirements also apply to the plugins and external CSS stylesheets used by the page, as these have the same considerations as javascript.

When this is not the case (sometimes called a “mixed script” situation), visitors to the site run the risk that attackers can interfere with the website and change the script so as to serve their own purposes.

Traditionally, browsers have run the mixed script, genuine or not, and notified you after-the-fact by a broken lock icon, a dialog box, or a red https:// in the location bar (in the case of Google Chrome). The problem with this approach is that by the time the script has run, it is already too late, because the script has had access to all of the data on the page.

Google Chrome now protects you by refusing up-front to run any script on a secure page unless it is also being delivered over HTTPS. Data on the page remains secure even in the presence of an attacker, but the downside is that this may cause pages to display improperly. You may wish to let the website owner know that their site is not properly secured. (Note that a poorly-written extension can also sometimes cause this).

You can bypass this protection by clicking “Allow Anyway”, in which case Google Chrome will refresh the page and load the insecure content. You will then see an https:// displayed in red in the location bar indicating that the page could not be secured."

Nice article though, really informative.

Phil A · Nov 6, 2011

Ta Axl,

Not sure what to do about that, my browser doesn't seem to like pics added from Photobucket either:(

Axl · Nov 6, 2011

I know what you mean. I've just loaded it again and clicked 'load anyway' and nothing on the site changes. There are no corrupt links, the image from photobucket is fine. I guess Google are just playing silly treetreetreetreetreetreetree :/

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