Effects of lime render & additives on an 1800's building

[mrb]

Hi Everyone,
I'm looking for some advice on the effects of lime render & additives on a 1800's building.

The builders working on my late 1800's listed brick and stucco building, have been applying a lot of render consisting of a 2/1/6 cement/Hydralime/Sand mix with pva & waterproofer additives to the east facing front & west side of my building.

I understand from the technical notes to these products and from speaking to their manufacturors technical departments that these additive products should not be used together in the mix because they have opposite properties and work against each other, but the technical dept's wont confirm what's likely to happen to my building i.e. if the products will just cancel each other out with no harm done, or if a specific harm will occur/ is likely to occur.

I also understand from the cement manufacturer that mix doesn't necessarily need cement tho' the local planning dept. does recommend using cement but in a 1/1/6 mix, which is less cement than what is currently being used.

The builders have ignored my concerns and carried on using the products. The council planning department hasn't replied to questions about my specific situation yet, and without solid evidence of potential harm, I would imagine the builders will not do anything about it, and I may just be over concerned.

Is my building is likely to suffer from damp or other damage in the future from the above material mix, and/or where else I could go to find out?

Thanks in advance for any help

MrB

 

[MdB]

(not an expert)
Your builders appear to be using modern building methods on a traditional building. This generally doesn't work. I would tell them to stop until you have this issue sorted out.

As the building is listed, your CO should have been involved. Like for like repair doesn't need their involvement but I doubt PVA was around in the 1800's so the CO will very much frown. What was on the wall previously? Cement or lime?

If you wall is double skinned with a cavity then it doesn't matter much what goes on the wall from a damp point of view. If it is single skinned though, the cement and PVA will stop moisture evaporating from the wall and this may (not will) lead to damp internally.

The cement and PVA in the mixture will also make it very difficult to get off the wall without damage.

Hopefully there will be others along in a minute with a more expert view.

 

[Penners]

there will be others along in a minute with a more expert view.

But not just yet. Like MdB, I am no kind of expert.

However, for what it's worth, here are some points based on my understanding of advice that's been given on this forum.

The addition of some lime to your mortar mix does not, I'm afraid, make it lime mortar. Many builders today believe that the addition of some lime improves the flexibility of the render, and that may be the case. But the significant cement content, not to mention the other additives, will make the rendering impervious to moisture.

The seriousness of this is - as MdB has pointed out - dependent upon the structure of your walls.

The brittleness of the cement is also likely to make the rendering more prone to cracking, in the event of any slight movement in the building.

Given that the rendering has already been applied, then I don't think there's much you can do but live with this situation. And indeed, I don't want to sound like the voice of doom - you may suffer no problems at all. But I do urge you to keep an eye on the rendering in the years to come, and ensure that any sign of cracking is dealt with quickly and effectively.

 

[MdB]

But I do urge you to keep an eye on the rendering in the years to come, and ensure that any sign of cracking is dealt with quickly and effectively.

Cracking lets the water get into the wall behind the render and as it is cement, it can't get back out again. That is when you get damp problems internally.

Others have also stated in the past that lime / cement mixtures have disadvantages compared to either lime by itself or cement by itself and although popular 20 years ago are frowned on now.

 

[Schoolmarm]

Why on earth do the builders think they can put what THEY want on YOUR property?

Was it ever discussed or specified before starting?

 

[biffvernon]

First thing tomorrow morning, shout at them very loudly to STOP. Then make them a nice cup of tea with a packet of Duchy Original biscuits (hurry while socks last or you'll have to go to Waitrose) and tell them that on no account may they use ANY Ordinary Portland Cement on your building. And ask them very nicely to remove all the work they did yesterday. Now, before it gets so hard it will do irreparable damage. No more tea and bickies till it's all off.

 

[Lime]

Cement should not be used.
You are paying the builders so stop them ruining your building.

 

[MdB]

Oh and expect 90%+ of builders to disagree totally with what is being said here. Finding a builder that understands old buildings is difficult. As before, modern methods on old buildings don't generally mix well. What your builders are doing works fine on cavity walls as there is an air gap to stop damp transfer and modern walls are less likely to crack. The same isn't true on old walls that naturally shift and don't have the cavity.

 

[kevmiles1]

Under no circumstances should your builders be adding or using cement on a building such as yours. I would first of all tell them to stop immediately and remove all the render they have applied. Unforuntaely it sounds like another case of not using specialists would suggest you get someone who knows about old buildings in the future. Good Luck

 

[Flyfisher]

As it's a listed property you might want to get your CO involved. In my experience you'll get a wealth of good advice about what's really best for the property.

 

[Pford75]

Whereabouts are you? Some forum members may be able to recommend a local builder/surveyor who understands old buildings

 

[ian]

mrb wrote

I also understand from the cement manufacturer that mix doesn't necessarily need cement tho' the local planning dept. does recommend using cement but in a 1/1/6 mix, which is less cement than what is currently being used.

?????

 

[christianb]

Hi MRB,

From the info you've provided I'd tell them to pack it in and remove the stuff they've already put on.

I'm not saying that the finished product won't look good, but there are two core issues with cementitious renders on old buildings (which tend to be more flexible than modern constructions) and both have been alluded to already.

(a) It's not "if" the render will eventually crack, but "when".
(b) It will trap mositure in the brickwork and this causes all sorts of problems.

C.

 

[Lime]

mrb wrote

I also understand from the cement manufacturer that mix doesn't necessarily need cement tho' the local planning dept. does recommend using cement but in a 1/1/6 mix, which is less cement than what is currently being used.

?????

Quite!

But I think there may be some confusion between the "local planning dept.", building control and the conservation officer.
They are usually completely different and often have very little to do with each other.

 

[Lime]

Hi MRB,

From the info you've provided I'd tell them to pack it in and remove the stuff they've already put on.

I'm not saying that the finished product won't look good, but there are two core issues with cementitious renders on old buildings (which tend to be more flexible than modern constructions) and both have been alluded to already.

(a) It's not "if" the render will eventually crack, but "when".
(b) It will trap mositure in the brickwork and this causes all sorts of problems.

C.

Yes, quite right.
Also I'd add it is almost guaranteed that in future there will be damp problems associated with the use of cement on the lime based building.

 

[mrb]

Thanks for the feedback to date. I've tried to answer some of the questions you've asked about my situation, which explains why I haven't yet been able to adopt some of the suggested courses of action...and as of now, the builders have stopped work on my property at the moment.... so maybe they are reading my letters.

I can't control the builders much, because I'm a leaseholder with a London council landlord who is responsible for the upkeep of the building structure, I just have to pay the subsequent bills + markup. The landlord sub-contracts the work to builders who are supposed to do "schedules of works" for me, and post survey - pre- works - on site visits with me but don't or haven't yet, despite repeated verbal and written requests from me. Also the builders sub-contract the work to other builders etc. which doesn't help communication or quality control.

I brought up the business of the builders using natural materials last year, during the builders initial survey, so I don't know if the builders have decided not to do pre-site meets with me, so I don't ask them incur any work they don't want to do, or want to pay upfront for.. or maybe its just competence levels or overwork.

Criticism of the builder reflect on the councils choice, so I'm not expecting much support from the CO against the council's favoured contractors. As far I can tell the contractor doesn't put in any LBC applications, and various of the contractors sub contractors that I've had working on my property, haven't known that they were dealing with a listed building.

When I've asked the local planning department if council contractors have to apply for LBC permissions i don't get any reply.
I'm also aware that councils and their suppliers can have long memories and be very very unhelpful to people that take them on, which is again why I need proof that I'm correct before I try to get them to change their ways.

I don't get the impression that conservation is very high priority compared to housing need, which is why I assume the council builders get to do what they want.

So when "my" council approved builder come back to me and tell's me that they are going to leave the render as is, because I don't know what I'm talking about and explains how much building and technical experience they have compared to me, are there any respected technical authority/ experts I can quote as well as those from SPAB?

I ask this because I know I'm right on the misuse of additives; however arguing for no cement in render is against the council guidelines ( which I assume come from the CO's as they deal specifically with care of listed or historic buildings) for at least a few major London councils e.g. Westminster, which has a "A Guide to Care and Maintenance - STUCCO" which recommends using lime/cement/sand mix ( tho not additives) in the render/stucco for some listed buildings.
http://www3.westminster.gov.uk/spgs/publications/Stucco.pdf

Do I need a specialist survey on the actual make up of the building before I can argue the case with the builder? 

( I've asked the builder if they if they have had the existing mortar analysed ( to know what they're using is appropriate) but they've not replied to me yet.) As I understand from the westminster guide that" Portland cement was commonly used in london buildings from the 1850 onwards" and was "used extensively by developers, for stucco cornices, window surroundings and other stucco decoration."

If I do need a mortar/render analysis and/or general listed building survey who should I go to? how much is it likely to cost me?

 

[Pford75]

From your very helpful summary, I would personally suggest that you need to approach the landlord in the first instance.

1. Point out that you are not happy that the work is being done to your requirements and you are therefore not prepared to pay for it until you are satisfied that it has been done correctly. State that you have tried to resolve with the contractor but are not receiving any response to your letters.

2. Send a letter via recorded delivery to the landlord (the council) advising that you are concerned that there is work being done to the property without the required LBC. Ask him to provide either copies of the consent or written confirmation of 'no consent required'. Advise that you will be contacting the Conservation Officer in xx days if you don't receive this.

3. Write to the CO and head of planning (both by recorded delivery) informing them of what you consider to be inappropriate works, which do not have consent and asking for their view.

Hopefully, you will not have to do 2 & 3. But since you are paying for this work (regardless of whether you own the property), you have a right to ensure that it is done properly and to your requirements.

 

[Schoolmarm]

And, I think portland cement in the 1800's was nothing like the cement being used today.

 

[biffvernon]

Too right - Portland cement hadn't been invented in 1800.

Portland was developed from cements (or correctly hydraulic limes) made in Britain in the early part of the nineteenth century, and its name is derived from its similarity to Portland stone, a type of building stone that was quarried on the Isle of Portland in Dorset, England.

Joseph Aspdin, a British bricklayer, in 1824 was granted a patent for a process of making a cement which he called Portland cement. His cement was an artificial hydraulic lime similar in properties to the material known as "Roman Cement" (patented in 1796 by James Parker) and his process was similar to that patented in 1822 and used since 1811 by James Frost who called his cement "British Cement". The name "Portland cement" is also recorded in a directory published in 1823 being associated with a William Lockwood and possibly others.

Aspdin's son William in 1843 made an improved version of this cement and he initially called it "Patent Portland cement" although he had no patent. In 1848 William Aspdin further improved his cement and in 1853 moved to Germany where he was involved in cement making.[1] Many people have claimed to have made the first Portland cement in the modern sense, but it is generally accepted that it was first manufactured by William Aspdin at Northfleet, England in about 1842.[2] The German Government issued a standard on Portland cement in 1878.

http://en.wikipedia.org/wiki/Portland_cement

 

[Penners]

First thing tomorrow morning, shout at them very loudly to STOP. Then make them a nice cup of tea with a packet of Duchy Original biscuits (hurry while socks last or you'll have to go to Waitrose)

Thanks for the recommendation, Biff. Next time I need socks, I'll pop off to Waitrose.