Lime plaster and render – saving The Old Brewhouse

Long-lasting lime plaster for repairs

I’ve just done a few pre-winter repairs of the outside walls in spots where surface render has lost its grip on the clay daub beneath. To my surprise, chalk lime plaster bought in 2014 is still usable.

It appeared to have solidified under an inch or so of water. But after scraping at the surface it quite quickly began to recover its original consistency. Lime putty when stored properly lasts many years – I still have an old tub of it in good condition – and this plaster is simply putty, chalk and fibre.

It is not entirely traditional: it uses synthetic fibres and they last indefinitely in the tub, unlike haired plaster, where the hair begins to disintegrate after a month or two.

*Chalk-lime plaster – quick repair ahead of the winter*

The old plaster is not ideal, because it takes hard work with a trowel to get back to the right consistency. But having forgotten to order a new tub, it’s good enough to protect small areas of exposed clay from rain and woodpeckers for a while. Next, I must order a new tub.

Chalk-lime plaster used externally has proved extremely effective over the years in temporarily patching areas of old wall that we haven’t fully repaired yet. A thin layer behaves almost like a sticking plaster over the cracks where old render is beginning to come away from the wall. Once cured, it has considerable strength and resists tearing.

There’s one quite large patch where the old render has almost entirely lost its grip on the clay – tapping reveals a hollow behind – but plaster over the cracks has kept it in place for the last few years.

It’s admittedly a bodge, but we wanted to delay full repairs as long as possible while effort and money went into other priorities. In due course the whole of one gable and about half of one wall still await a full overhaul.

Both will be a challenge. In the days when our house was part of a farm, a lot of running repairs on the clay were done with cement render. A bit less than a third of the walls is still cement render. The rest is our past repairs and some areas of wall that have been untouched for many years.

The latter are not even rendered, but are clay daub covered with many coats of limewash over a long period. The limewash has built into a thick layer that, until we examined it closely, we thought was in fact a render. So our farm building’s exterior walls may once have been rough clay daub given a protective limewash.

Cracks

The hot, dry weather has produced many more cracks than usual in our front wall.

Much of it is plain clay daub with thick layers of limewash and here and there a smear of recent cement where previous owners had tried to stop the clay falling out. There is no evidence of it ever having been rendered or plastered on laths. Continue reading “Cracks”

Back to 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. Continue reading “Back to daub”

PS on lime

I gather that there is questioning among some East Anglian lime specialists of the claim reported in the previous post that traditional hair mixes are significantly prone to failure.

As I mentioned, this is not about the well known deterioration of hair if it is left too long in a wet mix before being used, but about intrinsic faults in the hair, especially if it is imported. Continue reading “PS on lime”

Back to tradition – lime plaster

We’re using lime plaster to finish the outside walls. Lime is a fairly recent revival as a building material, and people are re-learning the old trades as they go, so there are still a lot of disagreements about the best way to do things. It’s not yet Lime Wars, but there are regular skirmishes.

Lime plastering the outside — Lime plastering a gable

As we’ve noted before, the Essex way (as taught on a course we attended near Braintree) was to use lime and sand as a hard render on the outside of a wattle and daub house. We repaired a wall like that, only to be told off a year later by a local Suffolk expert: the true vernacular coating in Suffolk was a plaster made from chalk, hair and lime, which is tougher and more flexible. Continue reading “Back to tradition – lime plaster”

Removing cement render – 2013

…. in preparation for the extension

Repairs on a building this age are never really finished, but there is a list of essential jobs we want to do before starting on the extension, for which we won planning permission in late 2012. The first step is to finish the external repairs to the end of the old building where the extension will be built. This means removing a large amount of cement render. Continue reading “Removing cement render – 2013”

Moving on – chalk and woodwool boards

Our thinking has moved on from when we started work in 2009 and 2010. One advantage of repairing a house very slowly is that it gives time to learn as you go along.

This applies particularly to the question of which materials to use when repairing walls and infill panels and when plastering and rendering, and to the question of energy efficiency. Continue reading “Moving on – chalk and woodwool boards”