Marianne Suhr: Limewashing exterior walls

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The project: Corner Cottage, an 18th-century, two-bedroom, rubble stone house undergoing restoration.
This month's challenge: To limewash the repaired exterior walls.

Last month we featured the first part of the restoration of Becky’s little rubble stone cottage (rubble stone being, specifically, stone masonry with irregularly shaped stones bonded by mortar). With volunteer helpers we removed the modern masonry paint and cement mortar from three of the exterior walls then repointed with lime putty mortar. The modern materials were trapping moisture within the walls.

While some people might relish the idea of revealing the rough, uneven texture of the rubble stone exterior and leaving it as the finished surface, it would be historically inaccurate for the period of the house. We now know that nearly all rubble stone walls would have been covered, at the very least, with limewash – white or pigmented – painted directly on to the stone.

For grander houses, rubble stone would have been rendered or roughcast with lime plaster. Becky was keen to put back an authentic finish to her house, so we enlisted some more volunteers and set about mixing our own limewash.

I love the simplicity of limewash – all you need is a tub of lime putty that can be bought, all over the country, from your local lime supplier. Becky had an old dustbin for mixing in, and laddered tights that made the perfect sieve. While we all agreed that the house needed limewashing, the subject of colour was contentious and it was hotly debated over a cup of tea and a chocolate biscuit.

Colour conundrum
I already had a tub of powdered earth pigment that had been left unused in my garage for several years, just waiting for a good home. Called ‘Marigold’ it produced a glorious salmony pink hue when added to the limewash, but Becky’s fiancé Robin insisted that he couldn’t possibly live in a pink house.

I tried to explain that it wasn’t the usual sickly pink colour of masonry paint, but a gorgeous, deep traditional shade that would make the cottage look quite beautiful. Despite my hard sell, Robin was having none of it, and was determined that this was an affront to his masculinity. We then had a play with yellow ochre. A tiny bit will create a creamy off-white tone, a larger quantity can produce a rich yellowy orange.

The great thing is, because limewash needs five separate coats anyway, you can experiment with different tints in the early coats and if you don’t like the colour, simply paint over it.

In the end I decided to leave Becky and Robin to make a decision and they opted for a clean, sharp, white. I continued chipping away at the masonry paint to prepare the surface.

Suddenly a big flake came resolutely away, and underneath I found a miniscule trace of the original colour – guess what, it used to be pink (but don’t tell Robin).

Limewash recipe:

You will need:

• Clean plastic dustbin
• Tub of lime putty
• Trowel or scoop
• Electric drill fitted with circuit breaker and whisk attachment
• Bucket
• Jam jar
• Earth pigments
• Old tights
• Goggles and gloves

1 Wearing goggles and gloves fill the dustbin part full with water and add the lime putty at a ratio of about 3 parts water to 1 part putty.
2 Mix thoroughly with an electric drill until it is the consistency of semi-skimmed milk.
3 Sieve the limewash by knotting the legs in the tights and placing over the bucket. Pour the limewash through.
4 For tinted limewash, mix the powdered pigment in a jar of water and shake well. Add to the limewash until the required depth of colour is achieved.
5 Wet the wall using the hose before applying the limewash. Brush the limewash well into the surface and allow to dry before reapplication.
6 Once the previous coat is dry, dampen the wall and apply the next coat. Continue for 4-5 coats on bare surfaces.

Expertise: Removing old masonry paint

• For rubble stone, it may be best to chip off the paint manually; use a ‘scutch’ hammer.
• For finer surfaces such as brick, dressed or ‘ashlar’ stone, a chemical stripper is more gentle and less likely to damage the substrate.
• For carved stone and fine detail, consult a conservator who may recommend the use of specialist equipment.

WORDS & PHOTOGRAPHS MARIANNE SUHR
Featured in the January 2010 issue of Period Living