Straw bale construction

[Andy Dingley]

Yes, but the _really_ real stuff is lead-dried. 8-)

The lead drier works better with high humidity, manganese driers with low humidity. Lead-dried oil is also more flexible and is essential if you're trying to make oilcloth. The best formulation (and that used for centuries) is a mix of both. A mixture is the one that avoids the shrinkage problems.

If you're using it for rifle stocking, you also care about the residual acid levels, which many of the supposed "authentic" makers are somewhat lax about.

There are very few buildings where it's important to use lead paint for authenticity. However there are rather more bits of engineering that aren't "buildings", where it's much more appropriate. Trying to convince English Heritage (or Cadw, in this case) of this need for a non-building is a whole new can of worms.

[biff]

I know of a couple of Lincolnshire windmills, the Maud Foster, Boston and the Five Sail, Alford, that use lead paint on their sails.

The Sweedish Allback TiO2 + manganese drier linseed paint that Holkham Paints sell comes with a manufacturer's recommendation of a 14 year maintenance cycle - a coat of linseed oil after seven years then a coat of paint after a further seven years. This lack of labour, plus the reduced risk of timber rot under a truely breathable paint, plus the environmentally relatively benign ingredients, gives it a clear advantage over alkyd paints. The even greater durability of lead paint justifies its use in extreme situations such as windmill sails where small children are unlikely to chew it. But I wouldn't recommend it for straw bales - where is this thread going?

[Pete C]

Hi,

Copper napthanates (Cuprinol Green) and borates aren't too bad in this respect.

cheers, Pete

[Pete C]

What might have been a factor is soot deposits in the chimney containing hygroscopic salts. Had a quick search and found an interesting post:

Maybe if it only occurs with wood soot it would explain why loads of vic houses in London built on clay don't suffer damp chimneys in the same way.

In any case, lime mortar can be quite porous so even if the bricks don't suck up damp the mortar might do, though porosity isn't necessarily the same as absorbency.

BTW what wood were the sole plates of the old house made out of?

cheers, Pete.

[The Natural Philosopher]

It was soft 16th-17h centurey brick set directly in wet cvaly and the efflorescnece came up about 4-8" depending on whether it had rained in te last few days. It had rotted the floor boards in contact with it and the skirtings as well

We had sever problems in many areas as it transoierd The house had had the opute plinth injected, and here damage was ionfined to breaches in te outer skin roof and bargeboards - i.e. not rising damp, but penetrative.

However there were several internal walls built in the same way, and these had not been injected: Here there was considerable rising damp which made a mess of skirtings and wooden floors, and in a colder areas appeared to have rotted parts of the sole plates from beneath.

However it was hard to be sure, because the moisture levels in the old house were so hight that we had to run a lot of heating to keep it dry internally, and that probably meant condensation within the old and colder parst of the structure.

Naturally it had been repaired extended and bodged with a selection of more or less inapropiate techniques over the last 150 years

I can however vouch for the use of supermarket shopping bags (tescos mainly) as a crude damp proof membrane...

[bigcat]

yeah, there are a few possibilities, but I didnt think he was in the mood.

Rising damp does exist, and does happen, but the odds of any case of ground level damp being rising are very small. There is increasing evidence that indicates that almost all cases diagnosed as rising damp are in reality not rising. Which makes dpcs fairly pointless, even in cases such as these which have long been interpreted as rising damp.

Salt contamination causes absorption of water from the air, and is a particular problem with chimneys.

Condensation can occur when the bottom is in contact with a source of cold, eg wet ground.

Theres also penetrating damp, sometimes due either to the difficulty of repointing at or below ground.

I also question the exact mechanism of the common occurrence of green at the base of walls, often due to rain bouncing off the ground. If it were no different to rain, one would not expect to see the green, since it would dry almost as quickly after rain. I suspect the rain bounce may be bouncing water containing salts and dirt onto the wall, which are hygroscopic and plant food. Having this on the outside of the wall will worsen the odds of the inner side staying dry.

NT