HAIRED LIME RENDER ISSUES

[tobydog]

We're members (Friends) of the Suffolk Preservation Society. We joined them after they helped us out in a dispute with Babergh planner over the apparent need to paint our oak clad extension black. Thankfully we won but that's another story which I know I've told before, however, we now get their half-yearly 'Suffolk View' magazine. We have just received their Summer edition which has the usual interesting articles and features but there is one I thought some of you might like to read about.

The article is titled "Holding on by a Hair's Breadth?" and relates to a surprising increase in the number of new lime render failures where hair has been incorporated. I would like to share this with you but I can't attach PDF's to posts (I've tried and failed). It's only two pages but over 630KB - any ideas?

 

[LadyArowana]

Once they have it on their website you will be able to post a link to that.

 

[tobydog]

Thanks Lady A. Unfortunately I don't recall how long they take to upload it so they are still on Spring 2012. Just trying to find a quicker way of doing it.

 

[Flyfisher]

I think only jpeg photos file can be posted here.
If it's only two pages, you could try converting it to two jpeg images. Photoshop can certainly do this and probably many other image programs.
You may need to tweak the quality setting to get a 'readable' photo, depending on the size of text, but it might be worth a try.

 

[Keithj]

Thanks for the pointer. I hadn't heard of them, and am in the process of joining.

If you have webspace, put a PDF of the article there and post the link here.
If you don't have webspace, e-mail the pdf to keef at keef dot org dot uk and I'll put it on mine and put the link in here.

 

[tobydog]

Thanks Keith. It should be on its way to you as I typed. Thanks for the other suggestion FF but that was beyond my capabilities, at least in the office .

 

[Keithj]

Click here to see the article.

It's a PDF, which most web browsers can handle with no further ado. Otherwise, try Adobe Acrobat Reader (free).

 

[Flyfisher]

Thanks for the other suggestion FF but that was beyond my capabilities, at least in the office.

Probably just as well, it was a bit of bodge suggestion. Keith's solution is far better.

An interesting article, though I was a little surprised to read the possible factor described in point 9. I understand the mechanism described, but I thought winters were historically colder than those we have now, so I'd have expected that factor to have been even more prevalent historically.

I also wonder if hair failure is definitely a modern issue. If not all modern hair renders exhibit these problems, is it possible that historic hair plasters also suffered the same degradation? The C17 example mentioned in the article would suggest this might be the case. Such renders are likely to have been replaced over the years, leaving no evidence of such failures.

 

[Keithj]

It's an interesting article, but it does seem to be missing some of the "known wisdom". Clearly, they didn't speak to the folks who did our house.

We had a particularly capable lady as brains of the outfit that carried out the repairs. They removed large amounts of concrete and replaced rotted-away sole plates before fitting the studs, laths, etc and rendering.

She insisted that the lime rendering had to be done after the risk of spring frosts was past, and that the hair had to be English, added in good quantity to the lime immediately before application, and that the haired lime had to protrude well through the gaps in the laths. She reckoned that haired lime needed to be used within a very few weeks of adding the hair: the lime needed to carbonate sufficiently to support itself by the time the hair had been eaten by the lime.

The haired lime was put on in a relatively thin layer, scratched to allow the next layer to adhere well. It was VERY hairy! The second coat went on about four weeks later.

She also favoured a render made of lime and chalk, with no sand. This is apparently not general practice, but known in Suffolk.

It's over a year since the lime render was applied, and I've seen no signs of deterioration.

 

[worms]

An interesting article

Indeed!

... though I was a little surprised to read the possible factor described in point 9. I understand the mechanism described, but I thought winters were historically colder than those we have now, so I'd have expected that factor to have been even more prevalent historically.

Is the suggestion that it is only haired, external renders that are failing? So the same hair used for internal plasters is working OK? If that is so, you could surely rule out all the factors (probably 1, 3, 5, 6 & 8 on the list) that might be common to both situations. The 17th Century plaster analysis quoted was on an internal plaster. How much evidence is there for hair in external renders from this period?

 

[robgil]

I amy be wrong but the chalk plaster, as far as I know was used more internally than externally , although I have read that somebody found a chalk rendered house at one time.
There is a chalk rendered house here in Walsham somewhere but this was applied 10 or so years ago.

 

[rebeccac]

Any chance of a recipe for the chalk/lime plaster as I'm experimenting with this in Italy and I'd love to know the quantities?

www.myabruzzohome.blogspot.com

 

[robgil]

I was using a 50/50 mix of putty and soft chalk, you might find chalk hard to get hold of in Italy? Anyhow it will depend on the temperature and humidity as to how wet you make it. I used goats hair in mine. You can also add sand to it if you wish.

 

[gill lime]

A number of colleagues across the UK and I have experienced lime failures in recent years. On analysis the common factor was the lime brand (regardless of whether it was NHL or fat lime). One of the problems was very slow carbonation even in favourable conditions - a symptom of this is that reinforcement hair is degraded due to long exposure to uncarbonated lime. We do not experience these failures using lime from other quarries. Perhaps, therefore, the degradation of hair is a symptom of another problem and some analysis of the lime used in these cases may be useful?