Re- rendering chimneys

[tulipcocoa]

The render on our chimneys is cracked in places and sounds hollow when tapped. Our architect says that the render is cement based and the replacement render should be the same. Is this correct? The building is listed and I thought we should now be using lime based render.

Appreciate any thoughts/advice.

 

[BMcD]

It depends if it was listed as having cement based render I would have thought. The person to ask is your Conservasion Officer they should be able to give you an answer

 

[NT]

Cement can permamently damage many building materials, lime doesnt. Cement traps damp, lime lets it evaporate. Cement breaks in response to building movement, or causes the brick or stone to break. Lime does neither, it microcracks then self heals.

So yes it should be lime.


NT

 

[BMcD]

But if it's been listed as a cement rendered chimney then a cement rendered chimney it ought to be. Not everything listed was built with lime you know.

 

[NT]

If its historic cement, as might be the case, it should not be replaced with modern cement, which is much stronger and liable to damage the brick or stone. That leaves the question of what to use. However in most cases lime is the right answer.


NT

 

[sarahj]

Our stone cottage was listed in 1986. However, it has many years of patchwork repointing done both before and after listing, yet just because it was done before listing does not meen that that was correct or that the CO would approve of replacing it with the same.

You could probably 'get away' with replacing it 'like with like' and not getting permission for it, but the CO could well suggest that lime render would have the most benefitcial affect on the structure (which is after all what you would presumable want). If indeed it was originally rendered in cement at the time it was built then fair enough!

 

[NT]

If it OTOH it had /original/ cement on at time of listing, replacing with modern cement would not be a like for like repair. FWIW.

NT

 

[Gervase]

Houses have also been listed with uPVC windows and Sandtex paint. it doesn't make it sound a practice to use them.
But, to be on the safe side, ring up the council's conservation officer and run your plans past him/her.
If s/he does insist on you using cement, let me know ASAP, as it will help enormously with some research I'm doing at the mo.

 

[Nemesis]

I do think that the architect may be thinking along the 'like for like repair' basis, but that isn't always the best thing to do - it all depends.

I suspect that the chimney render is a later - much later - addition. When was the house built? What does the listing desciption say?

 

[tulipcocoa]

Thanks everyone! Next stop the Conservation Officer. The house is part Georgian/part Queen Anne (I think). The listing doesn't refer to the render as far as I am aware.

 

[BMcD]

If a building is constructed or altered with materials using modern cement and consequently considered to be of architectual impotance and therefore part of our heritage then it is right and proper to use modern cements in any repairs.

NT wrote:

If its historic cement, as might be the case, it should not be replaced with modern cement,

At what point do historic cements become modern and useing lime instead of a "modern" cement where an "historic" cement was used would be less in keeping with the feel of the building than useing "modern" cement.

I accept that as it transpires lime in this case is probably the corrrect way but as a further question, can the CO say that since the render is coming off and since I (the CO) don't believe it was ever intendend to be rendered
you then have to renovate the brickwork?

 

[Nemesis]

In many cases, the use of cement in a historic building is a modern one - eg pointing - and it can be damaging, both to the material to which it is applied and to the way the building functions. So if the opportunity arises to replace it is better done with non-damaging material eg lime.

There is most certainly a case to be made for the best solution for any building - in this case removal and re-pointing may be the most acceptable solution. Recording that cement was removed is possible.

Early cement buildings, such as Castle House, should be repaired with cement - although as that was so experimental it's probable that different formulations will have to be used, as early cement mixes didn't prove really too durable.


Conservation isn't always about things not being able to be changed, if such change, carried out sensitively, ensures the furure of the building.

 

[BMcD]

Nemisis I agree with what you're saying but you may be able to help with the point I'm trying to make.

Do you know of a building (in Kent I think) which started life as a tudor farm house or something and has had a major extension built in about 4 periods of architercural significance since. It was listed in the 1980s fell into disrepair and has recently been restored to the condition it was in when listed eg carved tudor panelling fully restored and then plasterboarded over to bring back to its condition at time of listing?

 

[Nemesis]

Possibly you mean:

http://www.nationaltrust.org.uk/main/w-vh/w-visits/w-findaplace/w-ighthammote.htm

A great deal of thought went into what should remain uncovered and what should be recovered - although I don't actually think plasterboard featured.

http://www.channel4.com/history/timeteam/2004_ightham_cons.html


[Open Image]

 

[BMcD]

Thanks for that. I just remember catching the end of a program or item about it and thought how interesting it was the way each layer in the buildings evolution has been restored even though much of the finished work remains hidden> But that now begs the question when does a building stop evolving and why can't alterations be unsympathitic to the character of a bulding so long as it's not damaging? After all it's all part of the buildings evolution

 

[Nemesis]

I think it's all a balancing act really - but there's a difference between aesthetically unpleasing and positively damaging, as cement so often is.

The former is often in the eye of the beholder it has to be said, and ideas change over time!

Not sure if this will work - here's an audio link to a Radio Four prog (Real Player needed) last item on the page:

http://www.bbc.co.uk/radio4/arts/frontrow/frontrow_20030730.shtml

in which Adam argued the case for Span Four being an important part of Paddington (listed Grade I) which wasn't the 'pastiche' it was claimed, and worthy of repair and retention.

After a long campaign Network Rail has agreed.

 

[NT]

NT wrote:

If its historic cement, as might be the case, it should not be replaced with modern cement,

At what point do historic cements become modern and useing lime instead of a "modern" cement where an "historic" cement was used would be less in keeping with the feel of the building than useing "modern" cement.

I dont know. Portland cements from the 1850s were much weaker, thus did not break bricks. Modern portland cement otoh does cause considerable damage, so would not make a suitable replacement in many cases. What the best choice would be, whether non hydraulic lime, hydraulic lime or an original forumla cement is beyond my knowledge.

IIRC the Concrete Castle was built with a total of 17 different cement formulae / mixes.


NT

 

[Nemesis]

And many of 'em haven't proved too durable. Much all a bit fragile.



[Open Image]


http://duckduckbook.wordpress.com/2006/07/17/35-twentieth-century-building-materials/

may be of interest...