More adventures in cob

Back from the lime course yesterday which I can heartily recommend to anyone currently residing in (or considering same) a period property which include stone built and georgian. Mike Wye runs this course several times a year and the first course of the year was completely booked.

But first the pics (I seem to have mastered the gallery function!). From left to right first pic is one of the crack in the wall with modern filling solution. Second is a close up of the concrete flue which needs to be removed and the hole in the wall repaired. Third photo was taken during the big snow of my favourite morning trees but this time from the office which was formerly impossible due to the chimney stack being in the way.

Back to the Course

The course was a little bit of most of the basic things that go into building and maintaining cob and other traditional buildings. The things that weren’t covered were working with mass cob or any joinery work. I personally would not want to tackle any structurally important work myself but would be happy to try plaster/render inside when the time comes.

Making cob blocks

I had the camera in my pocket but got engrossed in the course and didn’t take one image so you will have to endure my description.

To preface this I don’t reckon forming your own cob blocks/bricks is really a viable solution for most enthusiasts except for those who want to self build and are competent.

Treading: Fairly simply clay, straw and water are tread into a well mixed mass. The role of the bullocks was taken up by 10 course members in wellies. Jolly hard work too even on a cold drizzly day!

Fill the metal form: The next step is to put the web cob mix into a metal form which is roughly breeze block shaped and sized. Pack it in well using wellied foot. Once full . . .

Remove from form: making sure there are no stones in the way of the flat metal plate that is just smaller than the form, two people using excellent hold, lift and plunger action slide the wet block out of the form. Now leave to dry for 6-8 weeks.

Building the stone base:
We went through stone work (very difficult for someone like me who is rather picky and slow) There is definitely an art and an eye needed to do this work ‘quickly’. The stones are not uniform in shape. Don’t think I will tackle this sort of thing for important structures. I might have a go at remaking the well ‘housing’ though.

Pointing:
Again I’m not a natural but could be persuaded to have a go at removing shot pointing and repointing. I don’t have any traditional walls that require this though (whew!)

Plastering/Rendering:
This was the part of the course I was most interested in. It is a minimum of 3 stages but two of those are normally repeated.

Harling – basically flinging in a controlled and skilled manner lime render slurry at bare cob or brick walls. This is the key stage for helping the next layer of render to bind to the wall. Good coverage but thin. Very messy! Can apply the next coat of render in 1-2 days in ideal conditions.

Haired course – a much firmer lime render mix with hair teased in. The hair reduces slumping. This course can be about 10mm or so thick. The action of applying render is different to modern skimming plasters. A second coat of haired lime render/plaster can be applied. Hollows in the cob are filled with this plaster mix. Building layers are ‘roughed up’ to create a key for the next layer. A slow process as it needs to ‘dry’ and times between coats can be 7-10 days in ideal conditions.

Smooth (unhaired) course – Internal work – this is a slightly looser mix (think ever so slightly runny porridge). The first course of this is about 1mm thick. At this stage internal plaster can be sponge finished and you are done. Or you can add a second finer plaster. If you add a finer plaster the coat is finished with a devil float which is just a wooden float with a nail slightly protruding. I quite liked the look of that but the final coats of plaster cover it up.

External work is slightly stiffer and thicker but again you can finish it with a sponge and tight circular motion.

Other important details

The lunch was in an old pub at Shebbear. I was too knackered to notice the name! However, excellent food and divine chocy fudge cake!

Closing

Buckland Filleigh is a bit tricky to find! But I didn’t go too wrong except when I doubted myself. This was the first time I had driven somewhere that is totally unfamiliar to me since Steve died. Steve was the navigator and map reader as I am hopeless at it. I left at 6.45 for a 9.15 start and it took most of that time. Got back in plenty of time to fetch Socks from the vet. He is still not himself.

What next?
Monday the builders show up to replace two windows in the extension and replace the guttering. Yeah!