Exterior lower wall black paint for Devon cottage

[Been_There]

Hi Folks - any ideas? I am living in a typical 400 year old Devon cob & thatch cottage on granite footings. On the exterior walls the white is really solid and thick, but the 40cms of black on the bottom of the walls is rather worn and tatty. Is there a special type of paint to be used for this, and are there any essential preparation works that need to be done first?

 

[DJH]

Hello Been_There. What an apt name that is. We all of us have been there for certain. I don't know the answer to your question but it was in danger of falling off the page. In the days before I knew better I would have said that black weathershield type paint is best but not now!!

Someone will come up with the right answer for you I've no doubt. Where abouts in Devon are you roughly?

Doug

 

[vicky whitworth]

Hello, we live in a rubble stone cottage in Devon and had the same issue. I'm pretty certain I sought advice on this forum and the view was that it was tar/bitumen that was used in the past, and Weathershield these days. It's a tricky one as my understanding of its purpose was to weatherpoof the lower part of the walls from the drip splash up as rainwater fell off the thatch. But in doing so it stuffs breathability. I decided not to have it on the rubble stone walls which are limewashed down to the ground - and have a nice high-tide mark showing where the walls are damp. I suppose some people might not like this but it doesn't bother me. Then on the modern extension which has a modern dpc with lime render above I have used Weathershield black paint up to dpc height. Some people might also not like that one half of the house looks one way and the other half is different. But I have one half of the house painted black and white and the other painted blue, and it has been said that I'm not normal. It was two cottages hence the intention to differentiate.

As Doug says, where in God's county are you?

 

[Been_There]

Hi Folks - Thanks for your responses. I am high up in the Teign Valley, well away from the valley floor and above the main spring line, so, as you say, it is just a question of dealing with drip splashes on the lower walls - luckily the thatch has a really good overhang, and the house is south east facing and well sheltered behind, so avoiding the worst of the weather.

 

[andrew gayton]

pure coal tar not bitumin.

 

[Penners]

pure coal tar not bitumin.

That's an interesting comment, Andrew. Could you give a bit more information, please? What makes coal tar suitable, whereas bitumen is not? I confess that I'm not sure what the difference between the two substances is.

 

[andrew gayton]

coal tar, on drying, is actually vapour permeable (it has almost a cryptocrystalline structure) where as more modern products are film forming and not permeable. coal tar dries to a very matt finish while thye latter does not.

 

[Penners]

A day when you learn something new is to be treasured.

Thanks, Andrew.

 

[CliffordPope]

Here's the stuff:

http://www.promain.co.uk/product/_Refined_Coal_TarBrushing_Tar_25_litres_id3646


Also traditional marine chandlers, especially narrowboats.

 

[worms]

coal tar, on drying, is actually vapour permeable (it has almost a cryptocrystalline structure) where as more modern products are film forming and not permeable. coal tar dries to a very matt finish while thye latter does not.

That's really interesting. How does that differ chemically from a coal-tar-derived creosote?

Without ever having looked into the science, experience suggests that exterior damp timber painted with creosote dries out, suggesting that the creosote prevents water ingress but still allows a degree of water vapour movement out of the timber.

 

[Penners]

Hasn't creosote been banned by the Wise Men of Brussels?

 

[worms]

Hasn't creosote been banned by the Wise Men of Brussels?

Yes, banned for non-professional use. But so has coal-tar.

 

[andrew gayton]

when one goes to order coal tar, the supplier will ask if one is a 'professional operative' - how one answers this will dictate the suppliers decision on allowing one to purchase said coal-tar.