Exposed Cotswold Stone Wall Needs Sealing

[Aidan]

Cement behaves like Goretex? Cement mortar behaves like cement mortar. Even Goretex stops acting like Goretex after a surprisingly short time.

A wall will absorb some of the driven rain. Also the wall is permeable and airborne water vapour will penetrate it from both inside and outside. When it stops raining, the water in the wall will evaporate through both the inside and outside surfaces.

In the UK we have to heat our houses for about 6 months of the year. The warm inside air can carry a lot more water vapour than the cold outside air. The usual mechanism is that the moisture is entering the wall from the internal surface and evaporating from the outside surfaces, but it is constantly changing with the internal and external conditions.

You seal the outside surface at your peril. I'd suggest you might find it interesting to research interstitial condensation before you commit yourself..

[biff]

Quite right, Aiden, er... except that my point was that cement does NOT behave like Goretex (at least not when the Goretex is acting like Goretex and not like my anorak which does not keep me dry when it rains

- right again Aiden)

[Mike]

I bet that's what the people who paid for it wanted to builders to do before they went bust :-)

But I do see a lot of these ties appearing when a simple re-build of part of the structure would do a far better job to my mind.

[Mike]

18th century ? Could they cast strong enough metal threads in those days or is this carved oak based ? Would love to see this.

Mike

[Anna Kettle]

Wrought iron not cast, therefore much stronger

Anna

~~ Anna Kettle, Suffolk, England |""""| ~ Lime plaster repairs / ^^ \ // Freehand modelling in lime: overmantels, pargeting etc |____|

01359 230642

[Anna Kettle]

If you are ever in Suffolk, give me a ring then. I love showing off my hovel :)

Anna

~~ Anna Kettle, Suffolk, England |""""| ~ Lime plaster repairs / ^^ \ // Freehand modelling in lime: overmantels, pargeting etc |____|

01359 230642

[Anna Kettle]

Whats the problem with that? I don't expect you do plastering for charity

Anna

~~ Anna Kettle, Suffolk, England |""""| ~ Lime plaster repairs / ^^ \ // Freehand modelling in lime: overmantels, pargeting etc |____|

01359 230642

[Anna Kettle]

I wasn't actually thinking of rising damp, which I agree can generally be traced to banked up earth or somesuch. More, I was thinking of the design principles of the house. Old houses were built with a bit of flex in them, a bit like bridges are built today so they don't snap in a strong crosswind. New houses are built with rigid foundations so they move as a complete unit and so there is less chance of the mortar cracking and allowing water to get in

I think its horses for courses

~~ Anna Kettle, Suffolk, England |""""| ~ Lime plaster repairs / ^^ \ // Freehand modelling in lime: overmantels, pargeting etc |____|

01359 230642

[Aidan]

"...my point was that cement does NOT behave like Goretex..." And I agree with you.

I think Goretex is made from stretched PTFE but it's vapour permeable property seems to be quite volatile. I read somewhere that about 80 days wear is all you can expect, not something that the manufacturers mention in the sales literature, for some reason. Not something you want to discover in the field. Micro-porous paint seems similar in that it's a good idea that is not entirely reliable.

My point was that, given the warm moisture laden inside air and the cold & (relatively) dry outside air during the heating season, the prevailing direction of travel of water vapour is usually from inside to outside, driven by the difference in the partial pressures. Putting a 'plastic mac' on a building will usually create more problems than it solves; the water vapour condenses when the temperature falls below the dew-point and the wall becomes saturated. The manufacturers' seductive literature is full of impressive before and after pictures, showing gleaming bright walls. The acid test would be to speak to the owners or monitor the moisture content of the walls after 5 or 10 years. Strangely, this is also something that isn't much mentioned in the sales literature.

[Mike]

Might be worth a trip. Didn't realise metal wall ties were so old. Do you have a more precise date on when it was installed ? Also any photos ?

Many thanks

Mike

[biff]

that it's a good idea that is not entirely reliable.

Yes, stay with real linseed oil paint.

[Anna Kettle]

The crown post tie was cut out at some point and the house started to fall apart - some of the timber joints have opened up 1.5 inches. I am guessing that someone panicked a bit and all the metalwork was put in at the same time to hold the house together. If so then there is a fairly precise date of ... umm if I remember rightly .... 1730ish cos elsewhere in the metalwork there is a device which is the precursor to the nutandbolt and which was in vogue for only about 20 years so I am told

I've no photos of the tie which is mostly hidden in the ceiling plasterwork so not very photogenic

Anna

~~ Anna Kettle, Suffolk, England |""""| ~ Lime plaster repairs / ^^ \ // Freehand modelling in lime: overmantels, pargeting etc |____|

01359 230642

[Mike]

I'm quite amazed they used metal for this purpose that early on when I would have thought such metalwork would still have been very expensive. How long is the tie ?

A real pity. I assume you don't intend to be re-doing this plasterwork anytime soon :-)

[Anna Kettle]

Maybe still cheaper than a new house? but I'm not at all knowledgeable about old metalwork. The tie is about 23 feet long and an inverted U shape. Cue ascii art:

------------- / \

[Mike]

Any ideas as to why they would have put it there in the first place ?

[Aidan]

I'd understood (engineeering background) that screwed fasteners had been made individually from wrought iron by blacksmiths until Whitworth established uniform interchangeable screw threads. I'm not certain of the facts. A bit of Googling found the Blacksmiths' Gazette home page (!) and this item;

"On a more modern reference, in the 1703 edition of Mechanick Exercises or the Doctrine of Handy-Works, Joseph Moxon refers to the screw-plate and its taps as a standard piece of equipment in the blacksmith shop. He describes the screw plate as having several holes in it, each less than the others. He says that these holes are threads grooved inwards, into which grooves fit the respective taps that belong to them. Sounds like the tap was made and then a hole was punched or drilled and a threaded hole was made in the screw plate with the tap. The screw plate was used to make the external thread and the tap to make the internal thread. A screw plate with several taps would be similar to a set of taps and dies today. I had recently researched this subject trying to determine exactly when screw threads were invented and the methods for making them in those early beginnings. If someone comes up with something better, I would be most pleased."

I think this would have been within the abilities of most smithies by early 18thC.

[Mike]

It wasn't so much the actual use of threads so much as them surviving the force that would needed to be applied to pull a house back together again that I found impressive for the time. Anna's tie was so long I doubt the average smithy could deal with it.

[DJC]

...

There is evidence that the making of screw threads in both wood and metal was known in in Greece in the second century BC. For a wonderful survey of Hellenistic Greek technology and science see Lucio Russo. The Forgotten Revolution. Springer 2004 (isbn 3-540-20396-6)

[Aidan]

It was probably hammer welded from shorter pieces of iron. This technique would also have been within the abilities of the local smith I'd think, but I don't claim to be an expert. At that length, it would have to be fabricated nearby or on-site.

[biff]

It wasn't so much the actual use of threads so much as them surviving the force that would needed to be applied to pull a house back together again that I found impressive for the time

Could it be that the tie bar's function is to limit further movement rather than to actually pull the house together again?