Lime render

[MetManMark]

All

We are looking to re-render our house shortly.It is a Georgian place that is currently rendered with sand and cement. The rear of the property hasn't been rendered and is stone on the ground floor, brick first floor but having done quite a lot of internal work we have discovered some cob primarily around the fireplace. Our question is regarding whether to render using pre-mixed lime or using NHL. We would look to buy the product from Mike Wye as we have had a fair amount from them and they have been jolly good.

Thoughts on relative merits would be much appreciated. Having tried unsuccessfully to upload images the house can be seen on google maps at EX15 1JY - at that stage missing a couple of chimneys at the gable end of the house but sporting security cameras (installed by the council when they rented the building).

We are using our regular builder who we have used a fair amount. He is confident using lime and has done his own house in NHL which still looks good.

Thanks in advance.
Mark

 

[MatthewC]

Have you asked Mike Wye for advice? I found that they were very helpful especially when I did my limecrete floor. I think NHL will set faster if that's an important factor in our current weather.

 

[plasticpigeon]

I'd have thought something with some hydraulic set, so something slightly hydraulic. Putty does take an age to carbonate and strengthen. NHL 3.5 does eventually go very very hard, almost like cement after a year or so. I'm not sure there is a definitive answer to this but I'd have though NHL2 or 3.5 would be a good compromise. Funny that you should ask, as on a forum such as this, one would think that some definitive answers to quite common questions would have been nailed down by now!!!!Maybe Joce will pop up and let us know what her very prestigious restoration builders are planning to use to render her very elegant Georgian cottage/house.

 

[JoceAndChris]

Oh sweet I was mentioned, I'm still waiting on Skillingtons. Where's Gervase when he's needed? Hopefully someone more knowledgeable can answer.

 

[Flyfisher]

Coincidentally, I was talking to our CO about this very subject today and was pointed in the direction of a hair/chalk lime mix.

However, I should point out that ours is a (mainly) timber frame house and this type of render is apparently ideal for a structure that will move slightly with the seasons, so I don't know if it would be suitable for a brick/stone building.

Some interesting reading here:

http://www.ihbc.org.uk/context_archive/84/summerling/one.html

http://www.anglialime.com/pdfs/HairChalkMix.pdf

 

[Keith Bowman]

I've used hair and chalk/lime from Anglia Lime onto wood laths and can agree that it is flexible, relatively easy and fun to use - but I was only patching a few square feet. I finished it off with a fine chalk mix, also from Anglia Lime.

 

[michael]

I would be interested to know if the existing cement render is original to your Georgian property or a later Portland cement addition?
Portland cement (an artificial cement) came along in 1824 but before that they were often using natural cements commonly known as “Roman cements”
Natural cement is more breathable than OPC but less breathable than lime. It dose however have a harder finish than lime and sets quickly, so it lends itself to things like stucco and façade detailing.
Natural cement seems to be almost impossible to find in the UK nowadays due to the onslaught of Ordinary Portland Cement but if it is part of the original finish on your building and you want to keep some authenticity, then this French product ‘Vicat Prompt’ is the nearest thing to it that is still available here.
http://www.womersleys.co.uk/acatalog/prompt_technical.pdf

 

[elizabeth]

The builder who worked on our cottage used 'Vicat Prompt', about a 30cm line along the bottom of our cottage as he wasn't happy with the lime plaster failing to cure there. The cottage is stone and cob up to 2m. and cob thereafter. We have a concrete path running along the bottom of the cottage which didn't help as the rain splashed up against the then lime. The 'Vicat Prompt' did develop some hairline cracks as it cured but it was much quicker at setting hard.

The rest of the cottage, as mentioned was rendered in lime with horsehair. We have a couple of fine 1mm cracks running vertically just on the corner of the cottage as a PO had built up the cob there using house bricks thus causing the cob, stone and brick to expand and contract at different rates. We expected this. On the whole we are pleased with the result. We are planning to render another wall of the cottage this year - we have a very high ground level to dig out first.