Feb
Cob Repairs – Repairing Hollows
There are many ways in which we can repair cob walls. Cob repairs may be required to a number of different issues, however the most important thing to remember is to try and use like-for-like materials where possible. Cob walls are made of very basic materials…clayey soil, fine and coarse aggregates and straw. Being mindful of these humble ingredients is crucial when introducing additional material/s to a cob repair.
Cob is made from clay, sands, aggregates and straw
This article will focus on the cob repairs to hollows that are sometimes found when the existing plasters or renders have been removed. Assuming careful removal of existing cladding/s has been achieved, the underlying cob walling can still throw a few curve balls your way…….like this one we uncovered recently.
Base of the cob wall exhibiting a lateral hollow
The hollow in the above image was revealed when we removed the top plasters. Running (from left to right) were 2 heating pipes (circa 1950’s) that had been installed by the [then] plumbers. Rather than surface mount these pipes, they decided to chase-out the low-level cob and ‘bury’ them into the wall. OK, these things happen. Structurally, the cob wall wasn’t compromised and I guess the plumber was delighted to have had such an easy time ‘digging’ the cob out to make way for the pipes – as opposed to grinding away at stonework all day!
Does this area actually need a cob repair?
This is a good point. Does it really need to be addressed? With a uniform thickness of plasters the cob would be stabilised and the end result would be satisfactory. The only downside to this approach would be the aesthetic ie the finished surfacing would be significantly different to rest of the cob walling locally and on other cob walls [within the room].
Another approach would be to incorporate cob bricks into the hollow, however in this instance, existing cob would have to be removed to accommodate for the depth of the cob bricks….thus negating our ‘preservation of historic fabric’ mantra here at The Cob Specialist.
The introduction of cob blocks and/or cob bricks into cob wall repairs is far from unusual. We adopt this method many times a year….but only where necessary and only where the existing cob fabric/s warrant it.
Let’s just recap on what we have here. There is a hollow in the base of the cob wall that is too shallow to introduce cob bricks and not shallow enough to accommodate a generous thickness of lime mortar. So, here’s what we do….
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