Back to daub

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Exposed clay daub

After focusing on  a new timber framed extension for so long, we’re now back to repairing the old building. Weak bits of of a rough cement render have been dropping off  the front wall, as the picture shows. The cement is just a thin layer skimmed a few decades ago onto clay daub.

We’ve been expecting this, but took a decision early on to let it happen by natural weathering, and then patch repair bit by bit.  Looking at the evidence of what’s there, we think patching is the way the walls have been maintained for a very long time – any weakness, then they just slapped on a bit of clay and limewashed it, and owners only recently took to adding cement as well.

In 2009, we repaired a lot of bare clay patches on both the front and back walls which were being ravaged by woodpeckers in search of insects. After attending an Essex County Council course at Braintree, we did all the repairs with a render of lime and sand.

Since then, as set out in previous posts, we’ve discovered that sand and lime render is not the authentic Suffolk method at all.  The local specialists use a plaster of chalk, lime and fibre on outside walls instead. Having done a gable wall that way, we’re now absolutely convinced it is best. Once limewashed, it is weatherpoof, it sticks much better than render to any substrate and when dry it is very strong yet still flexible. So no more clay, sand and lime render.

Instead, the plan is to use a new daub of clay and straw with a little sand to repair holes in the old daub. We have saved a few barrels of the pale grey boulder clay that lies under the house and pond for just this purpose. Its colour when dry exactly matches the clay exposed on the wall.

One option would be simply to limewash the clay, which as far as we can tell is the only protection it used to have. There’s a whole wall on the farmhouse next door that is clay protected only by limewash.

But because the exposed clay is rather fragile and crumbly, we think it is best protected with a thin layer of plaster to replace the cement render that has just dropped off. This will protect the old clay indefinitely.

How do I reconcile this with the decision to  completely re-render a big gable end wall with Savalit boards and lime plaster (see earlier posts)? The answer is that the gable had been rendered with concrete on wire netting, and all the concrete had to be removed. There was no clay at ground floor level, so patch repairs were not an option. The clay higher up would be protected by the boards. We’ll probably want to use the same method for the other gable. But there is enough clay in the front and back walls to make it worthwhile patching in the traditional way.

Other commitments will delay the work till later in the summer, but by then it is almost certain more will have fallen off. Below is a temporay solution to keep another large patch together. A quick application of lime plaster with chalk and fibre to the cracks is strong enough to stitch these pieces together for a few months longer.021

3 thoughts on “Back to daub”

  1. Enjoy reading this – your journey and deliberations seem to match ours – trying to think about what is best and why.

    We reconstituted some daub and then added more materials to it. Used clay, dug from the site, chalk and lots of straw. Don’t think we added any sand. The end result seemed to match the original. It was lovely to work with and had almost no shrinkage when it dried.

    1. Thanks for the comment. I’ve wondered about the usefulness of sand. Was advised to include it but not obviously present in the old daub. I’ll try leaving it out. Peter Rodgers

      Sent from my iPhone

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      1. Thanks – if it is any help we got the chalk from Needham Chalks – they do a fine one and one with lumps in, I preferred the lumpy one. Also, we used chopped straw such as they use for horses /animal bedding – saves chopping it yourself. Surprised by how much straw it could hold. Think we found animal urine in the old daub, but decided against adding any more!

        Of all the materials we have used on the house, daub has got to be the most satisfying. Will be repairing some internal walls with it soon. This time we have some old clay lump blocks that we will reconstitute – it will be interesting to see if they have any sand in them.

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