In defence of Cement

[Nemesis]

Part way down this page is a telling picture.

http://www.scotlime.org/news.asp

Most builders have not much idea beyond modern materials. Ask them. Thay have no training and expertise in the use of traditional materials in traditional buildings.

They tend also to do whatever is most expedient in the short term - if the problems happen years down the line, well, that's tough.

As far as lenders are concerned - most places won't fall down (and they make you insure, which is another can of worms) just be damaged.

The damage you pay for to be rectified, not the lender.

 

[Flyfisher]

Well, we've said our piece if you aren't interested it's your problem.

Not really, it's a heritage problem; not in the sense of culpability, but in the sense of the consequences.

For whatever reason, the use of inappropriate materials seems to be continually used to the detriment of historic structures. By definition, such structures are in limited supply and destruction is forever.

It's easy for experts to criticise and castigate all those who condone and carry out inappropriate work to heritage structures, but that's not really helping to solve the problem of damaged structures.

What good is expertise that, for whatever reason, is not effectively being applied to solving the problem?

 

[Nemesis]

Oh, I don't argue with that - as PPG 15 states, historic buildings are a finite resource.

But as far as one chimney goes, it's a great shame if it is 17th century to allow it to deteriorate further via a short term fix with slurry, but nowt really more we can do to prevent it. Not sure here we have castigated, but we have pointed out the problems and appropriate solutions. As with medical help, if the patient doesn't accept the diagnosis and won't take the medicine, that's in the end their health.

When developers are ever more keen to totally demolish listed structures for whatever 'justification' they make, one unlisted chimney has had a great deal of free expertise thrown at it and if its owner won't listen, sad but... it's his property. Which within the constraints of law he can do as he likes with.

So if you have any ideas and you can throw your expertise at it, do so.

I will be very interested in your solution, then, Mike.

 

[Flyfisher]

I don't believe I've ever claimed any expertise, Evelyn.

However, and please don't take this as personal attack, it may well be that experts and professionals, in any field, feel frustrated by the apparently reckless behaviour of people who blindly ignore the obvious evidence and expert advice against some particular action. But those same experts and professionals will have failed in their objectives if, somehow, they can't encourage a change in the reckless behaviour.

To continue your medical analogy, you're quite correct that if a patient refuses all medical assistance then they must bear the consequences. But it also means that the doctor has completely failed; he may as well never have existed because all his training and expertise has come to nought.

The doctor therefore has the choice of adopting a condescending 'I'm an expert professional and you must do everything I say or suffer the consequences you wretched little person' approach, or he can try to get inside the mind of the patient and attempt to understand why they are behaving, apparently, so irrationally. Only if the doctor does manage to understand the patient's perspective can he begin to understand the patient's decisions. And he may discover that, from the patient's perspective, they are not so irrational after all . . . at which point a more productive dialogue can begin, one that may well have a better chance of a successful outcome.

Of course, no one can know for sure if the doctor would be any more successful with such an approach but when the alternative is certain failure it must surely be worth a more humble, softly softly, approach.

 

[Anonymous]

You are all right the use of lime in traditional building repairs is far more appropriate, no question of that, I just don't think the risk of damage from cement is as serious as is being suggested. Thanks for all the links Nemesis I have looked at some of these, but for every wall you show me that has suffered cement related problems I could show a hundred that have not, I could walk out of my gate now and look at dozens of old houses neatly pointed with what is almost certainly some sort of cement mortar, some of our friends live in these houses, and I can tell you they have no problems with erosion or damp or rot or anything else that my be attributed to the use of cement. The medical analogy is a good one, a lot of people don't know what is bad for them, and a lot of people who do know, ignore it or do a risk analysis and decide the risk is to small to worry about, that would be me. I do have some experience of housing finance and flyfisher you are partly right, if lenders were receiving different advise regarding lending for improvements to traditional property, there would either be less money being lent or more appropriate repairs being carried out. The amount of outstanding debt for alteration to older property is huge, and the lenders exposure to risk is substantial, therefore as you and others have pointed out, if the risk of future problems really is that great, someone should be making loud noises. I should point out that in my earlier post I was not suggesting that any of the professionals on this site are in any way undertrained, but that personaly I would not want to take the advise of the two individuals who's experience with lime consists a one day basic training course over an experienced craftsman.

 

[Nemesis]

How long ago was the pointing done? Buildings differ, and time takes its toll in different ways.

And in my opinion - I agree with Biff, cement is hard, unsympathetic and inappropriate.

People are making noises. RICS is for example, but it takes time for training to alter.

Many experienced craftspeople and those who have taken rather more than a one or two day lime course ( who exactly was that comment aimed at?) will tell you the same as we have.

http://www.amazon.co.uk/Precious-Inheritance-Conservation-Vernacular-Buildings/dp/1905960018/ref=cm_pdp_review_teaser_product


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If you choose not to listen, well, so be it, but I suggest you look at the sort of work being carried out on important historic properties (such as cathedrals) and ask - why are those skilled craftspeople using lime? A whim?

http://www.stone-mason.co.uk/restore.php

http://www.stone-mason.co.uk/downloads/conservationreport.pdf

Try calling SPAB. free helpline, I am sure the skilled people there will tell you exactly the same.

HS has a raft of publications too, which are free:

http://www.historic-scotland.gov.uk/hs_publications_list_web_dec07.pdf

 

[biffvernon]

You are all right the use of lime in traditional building repairs is far more appropriate, no question of that.

Good. Let's just leave it at that then

 

[Nemesis]

a more humble, softly softly, approach

Well, we await your adoption of this with interest then Mike!

 

[michael]

I’m a bit late getting in on this discussion but I would like to play devils advocate just for one minute.
I don’t know when OPC was first introduced but my property dated 1880 which is of 9”solid brick construction is completely rendered in an original rusticated cement stucco i.e. cement mouldings of imitation stone block work and classical features. 128 years on and there doesn’t appear to be too many problems.
I understand the theories preached on this site and to every modern builder’s annoyance, I try to practice them, but my position on lime is often very hard to defend when I have a great big example of 128 year old cement starring everybody in the face.

 

[Nemesis]

Yes, and I've been involved with Bridgwater's Castle House, the II* Listed 'Concrete Castle', but I also wonder - have you ever had your mortar analysed? Is it modern Portland cement?

And do you think that in general hard modern cement pointing is suitable and aesthetically pleasing on traditional houses which were built with lime and were intended to 'breathe'?

And additionally, do you think that playing Russian Roulette with period buildings is a good idea?


http://www.buildingconservation.com/articles/mortgage/mortgage.htm


http://www.exmoor-nationalpark.gov.uk/enpa_historic_buildings.pdf


http://www.defence-estates.mod.uk/publications/historic_buildings/historic_buildings/PDF_8111/Technical%204%2001.pdf

 

[andrew gayton]

In my experience, It is not at all unusual during a lime v cement discussion to hear a builder say 'but I have been doing it this way for 30 years'..........

.............. to which I have to say 'yes, but you have been doing it wrong for 30 years'...............

Obviously,such does not happen when I discuss the repair of an 18th C and later building which included cement (be it keenes, roman or the later ordinary portland type) in its original construction............. although I have seen instances where roman cement has caused massive problems

An earlier post mentioned that a r.i.w'd and s+c rendered wall was 'still dry'............. maybe on the face of it, but I bet my boots that the core is sopping.

 

[glayzell]

I hope i cant show you here the difference between cement and lime as used on my house. It is a timber framed georgian property, the side wall in the lounge was repaired in the sixties and was rendered in cement over chicken wire, instead of laths and lime on top of the timber frame, the followinge was repaired by me 40 years after the original repair:

These two pictures show the extent of the repairs, i had to build an entirely new timber frame for the whole wall as it had rotten

this one is a bit out of sync, you can see the cement render square

In the dining room the wall had not been repaired, this was the extent of my repairs, 200 years after the house was built:

 

[Nemesis]

Interesting set of pics - many thanks for those.

 

[michael]

Yes Nemisis, I think it is Portland cement. I sent a sample off to Rose of Jericho for analysis and they kindly advised me that it was not worth paying out for a full analysis as they could tell just by looking at it that it was just ordinary cement. I also seem to remember reading somewhere that the sharp edge detailing required for stucco decoration could not be achieved with lime mortars as it was far too frail. In answer to your other two questions regarding (a) aesthetics and suitability and (b) Russian roulette, I guess that’s a question for the original builders of 1880 as nothing has been changed by me.

I live on the south coast and it would seem that all of the 5/6 story terraced houses on the sea front also have a painted cement render facade on what is either a brick or “Bungaroush” constuction. My feeling is that the resilience of the cement render is probably beneficial in this climatically quite hostile seafront position which is susceptible to salt ridden sea spray and gale force winds.

Just a thought though. Whilst my building is externally rendered in cement, the construction of the walls is brick and 'lime mortar'. The internal faces of the brickwork are un-rendered and un-plastered. Instead, and typical of that time, there are lath plaster panels connected to the internal face of the wall with wooden pegs and battens which effectively leave an air gap between the laths and the brickwork. Is it possible that the 9” walls are able to do their breathing from the inside?

 

[Nemesis]

Yup! Could be.

Renders from the 19th century are not as hard (in general) as modern cements, they were still a little experimental (and that at Castle House very much so - Simon Swann has analysed it all, and it's actually quite fragile) but these are really a separate issue.

Modern manufacturing methods have ironed out the 'problems' and it's all very different these days.

Where unusual constructions and historic renders are concerned, of course, as Andrew says, these need to be looked at individually.


http://www.donhead.com/journal_architectural_conservation/jac_13_1.htm

http://www.donhead.com/journal_architectural_conservation/jac_13_3.htm

http://www.minervaconservation.com/articles/abriefhistoryoflime.html

http://www.minervaconservation.com/articles/externallimerenders.html

 

[Stephen]

Sorry about being late into this one. An interesting debate.

Cement as we now it was 'standardised' in the 1920s when the British Standard came about This also helped bring about the downfall of Lime because it could not be 'manufactured' to a consistent uniform standard and therefore a BS could not be appled to it. Prior to the 1920s various forms of what we now call cement were used. Back in the early 19th century it was used mainly for underground and high exposure areas (e.g. lighthouses) and for engineering. In the late 19th century forms of it were used in mortar for house building. However at that time the temperatures used for firing were lower than used for modern OPC and late Victorian cement cannot be compared with modern OPC. The 'cement' used then was a softer material than the stuff we use now.

As a rule of thumb I was always told that the mortar pointing is the sacrificial bit of the elevation and should always be softer than the surrounding brick (stone, etc). This rule applies with all building materials, including modern bricks. As modern bricks are generally fired to high temperatures and are hard and dense they can withstand the use of cement. Whether problems will arise in years to come we shall wait to see. I have heard of some situations where they had to change to a softer mortar (lime gauged or pure lime) on modern buildings because of the need for flexibility in situations where there was a problem of thermal movement. Nonetheless cement has its uses and with modern buildings is less likely to pose problems.

With Victorian buildings that are constructed with a reasonably hard brick the use of old 'cement' has not necessarily caused probems and in some instances the use of modern cement will not cause problems provided the actual mix is not too strong.

The use of cement on many older buildings generally however is a problem. However, the word risk is very apt here.

Quite often a building can have cement applied to it and not exhibit a problem for decades and with other properties the problems become apparent fairly quickly (within ten years). I would concede that the majority of historic buildings fall into the latter category. However, note the use of the word 'exhibit'.

The real problem is that until the cement based finish is removed the real damage is not revealed. In some instances the damage may be minor and in others it can be extreme. I have seen both ends of the spectrum. Normally the use of an inappropriate material (here we are discussing cement) takes time to impact. How long (1, 2, or more years/decades) depends on the specific situation. Therefore the decision about what to do is complex, particularly if the superficial evidence of a problem is poor or lacking.

I choose to advse my clients of the risk and the possibiliy/probability of having to do something about it at a future date. How urgently I categorise this depends on what evidence there is, etc. Some of my fellow surveyors take the view that if there is no superficial evidence there is no point in causing unnecessary alarm. I do not share that approach and do not regard a warning of a future item of work as causing alarm. There are also many professionals (many good people when it comes to surveying modern buildings) who are blissfully ignorant of the issues due in a large part to their basic training, etc. The only time they find out about such issues is when they get sued.

In summary I would say that moden hard/strong/dense cement on almost any property pre-1920ish is inappropriate. Modern cement used in a soft gauged mix may do little harm to Victorian/Edwarian properties (exception being cement render on timber frames) but that does not mean I would specify it. Cement render on older properties usually causes more rapid degradation and damage (than where lime has been used) and should therefore be avoided. Where cement has already been applied to an older building each situation needs to be carefully assessed. The starting point should be "the cement is inappropriate" followed by a careful risk assessment that should conclude with how soon/how long before the cement should be removed and what are the likely problems that could be revealed when work starts. Where problems (e.g. damp, spalling bricks, cracked surfaces, etc, etc) are apparent I would normally regard cement as the prime suspect and advise accordingly, but taking care to consider all factors.

Ultimately it is a risk assessment that we are discussing here about he impact of a material that is known to be potentially damaging. Using the medical analogy - we all know smoking kills but can cite examples of some smokers living to a ripe old age, others die young (and horribly) and of course those who smoke choose to ignore the risks believing it won't happen to them.

 

[Nemesis]

Thanks Stephen.

On Castle House I seem to recall that the 'Portland' when analysed was six different types. It's very fragile and conservation an ongoing challenge I think.

http://www.bbc.co.uk/somerset/so/2004/04/castle_house.shtml

http://www.vivat.org.uk/news/news.cfm?ChunkID=currentlist&ArtNoId=ArtNoID98

 

[Flyfisher]

Many thanks Stephen, but one question:

Cement as we now it was 'standardised' in the 1920s when the British Standard came about This also helped bring about the downfall of Lime because it could not be 'manufactured' to a consistent uniform standard and therefore a BS could not be appled to it.

Can you elaborate on the problems with manufacturing a consistent quality of lime?

I can imagine that historical limes would have been all over the place but I'm surprised that modern manufacturing was unable to be more consistent. Or perhaps that was only the case in the 1920's?

 

[Nemesis]

BS EN 459-1 covers building lime classifications.

http://www.scotlime.org/trad_mortarspec.html


http://www.thenbs.com/topics/Environment/articles/limeMortar.asp

 

[michael]

Stucco renders from the 19th century may have been experimental but there seems to have been a hell of a lot of it done. It’s probably worth noting that some of our capital cities most important residential structures and urban estates would appear to be cement rendered or at least rendered with something very hard and painted in a shiny cream, presumably lead based paint to boot :-

Kenwood house, Clarence House (at least as far as I can remember), the entire Regents Park estate, The entire Mayfair estate are just a few. I could go on with many other examples such as large parts of Camden or Islington.

How about earlier examples such as the impressive regency squares of Brighton? not to mention the later period Grand hotel on the seafront. The earlier regency examples may not be rendered in cement but they are rendered in something very tough, durable and presumably unbreathable and again painted in a shiny cream paint which I think in that area is a specified colour called Brunswick cream.

I’m not deliberately trying to put a fly in the ointment here but owning a period cement rendered property myself, I really need to get my head around this. Is my property and those mentioned above likely to fall down in the next 50 years due to their inappropriate cement rendered design?