Using lime mortar for repair at a medieval hall house | The Landmark Trust

gluon Callen is a late medieval farmstead with a range of buildings from the medieval house itself to the hundreds of Beast houses and stables together they tell a story of the evolution of habitation and farming practice the LaMotte trust project to conserve and repair the site needs to take into account the range of both historic and future uses and ensure that we treat the buildings with honesty and respect preserving the surface texture of the site is critical to this process the repair of the fabric of the buildings the stone mortar and any external renders is done with appropriate lime mortars and materials Nigel Jarvis fruit in our line is an expert in lime mortar specification here he shows us how close analysis of the original building materials can help to define how repair work is approached so I think the interesting thing at looking at a building like this is the phasing the way it's developed where it's grown as a as a collection of agricultural buildings the way it's come from its surroundings the materials because we weren't able to store they weren't able to transport materials at that at that time obviously what it's constructed with how its constructed the quality of construction and how that's appropriate for its use so we got a gable end of a building built into a bank built with materials lots of fieldstone lots of rounded stones and not particularly useful stone for building really but they've they've they've used it nonetheless it's then bonded with or bedded in an earthen mortar and this mortar is very soft very crumbly it's really just earth that's been dug out and then mixed with quicklime from the kiln and you can also see remnants of firing material so this is would be in coal or coke that was mixed with lime fired the lime and then those will they mix together the earth and the lime mixed together to create what's called a hot mix and you can see that's what creates this passion ocean really soft really crumbly but actually very appropriate you know it's worked these buildings are existing standing they flex they move and the softness is their strength and they survive very very comfortably during their lifetime the buildings at Karine Callan had been added to and repaired in the last hundred years or so lime mortar fell out of fashion and non-porous cement based mortars were used for repairs to traditional solid walled buildings solid walled buildings rely on the breathability of their building materials to stay both structurally sound and healthy so here's what's happened over time his repairs have happened so cement has been used cement was then the material that was on the builders merchant shelf that was what was there that was what was convenient and that's what people got used to using and these repairs have happened the problem with this is moisture can then run down the face of the stone and because cement is impervious and brittle it often creates cracks but behind it and the moisture can run and get trapped inside the building and that moisture then accumulates and it's all a bit brutal it's a bit hard it's a bit insensitive before repairs are considered time needs to be taken to look at the causes behind any apparent structural problems so looking at a war like this where it was obvious failure and it's um it started to fall apart there then actually looking at the cause and it's a really simple cause and so often the cause is just poor maintenance and they need actually having no gutter on there at all would probably be better than having that bitter gutter which then concentrated all of that run and all of that bit of run on this and it's flushed the mortar out of the wall and this isn't the failure of the mortar it's a failure of repair and so often we find that's the problem it's actually not looking at how we're maintaining buildings it's a really simple and obvious thing to do we're all guilty of you're guilty of not doing that gentle ongoing maintenance before lifting at all we carefully consider the aesthetics of repair how much repair is needed how will we use the buildings and how do you want the site to look once the project is complete when I first come to a building like this I'm often thinking what is the minimum I can do I think we're often spending too much money and I think that we're often wanting to to Botox a building to sanitize a building and I think that that that approach of a gentle repair and minimizing what needs to be done safe identifying cause of damage and obviously removing that that that cause to start with before doing repair and I think in that way we can actually retain an awful lot of the building rather than changing it completely that then means that often you have this identification of chronology of a repair which I think is is really attractive and I think we should be encouraging that as as part of the progression of the building the building's at gluing Kalen have all decayed over the years in different ways some walls have suffered from lack of maintenance others from structural movement but they are all exposed to the elements which inflict to slow weathering a way of material so to a point waters in in the wall are are the wicking they're the breathing they're the element of the building which allows that flex and movement and moisture to come in and out they absorb the wetting and drying cycles the freeze-thaw cycles it inevitably happened in an area like this so you'll always find that to a point they will be sacrificial they'll they will decay daily Road and that's part of their function that's not a failure it's part of what they need to do but as you've seen on on areas where there have been damaged to gutters and those those protections for a building where that breaks down then it's too much for it to cope with but on a on a general basis if you have the the finished of the building appropriate or each elevation of that building the finish of each elevation appropriate to the weather that's hitting it then you'll get a slow sacrificing of say limewash which is very easy and cheap really to put back on the cider house was added onto the back of the main house sometime in the 17th or 18th century it is a functional building well built but was not well maintained most of the original mortar had washed out of the walls and it has been almost completely repointed so this was a building which had various elements to it which were were failing there was a lot of damage to the to the roof there's a lot of ingress in through the top of the wall because of damage to the stone tiles so that's obviously all being repaired you can see a new wall plates gone on new rafters and you're kicking board tiles over the top this understand is going to have gutters on it which is obviously going to protect this wall from rain sometimes these buildings didn't have gutters on them so that rain could be driven onto this wall so the finish of these walls is they've been lime washed and the lime wash then helps to protect the stone yeah obviously you can't see it now but the build-up of what's underneath here is pointing that's being repaired on a place where it's where necessary and in each situation when we look at a building we identify the materials that we need to repair it so the range of limes which we can use which have different qualities so you have fat limes which are very soft and flexible and breathable the other mortars that you can produce are from limes that are called hydraulic limes and hydraulic limes having purities within the limestone itself and those impurities contain silica and alumina when you fire them they become reactive and they give a faster set so there's a range of hydraulics NHL to three point five and five NH 10 NH L stands for natural hydraulic natural because those impurities are contained within the limestone so it's important to identify the building's needs it's important to identify the softness of the stone the appropriateness of the mortar that's going back into the to do the repair the mortar that's here is using a grit sand which is about three mil aggregate which goes down to a very fine sand and then another aggregate it's much finer and much redder and that fine aggregate gives it the pigmentation they then mix this with a mid range hydraulic line a three point five that means it's compressive strength is about three and a half Newtons and they mix that together to make up the mortar and apply it so prior to any of this work going on prior to any pointing or any Lyme washings what you needs to do is control the suctions they need to make sure that you're not putting a wet material onto a dry background if you do that then you'll lose the bond between the two there's what you do is you wet up the background and it means that you're controlling the suction of that background so the new material that you've put on can slowly bond into the surface it's crucial that you do that between each coat but also is what you see is when these buildings get wet the lime wash becomes more translucent that's not a failure with the material it's just a reality of how the material actually works the stable block is also a functional building but has fared better over time we were able to take a less intrusive approach to the repair of its walls and it became a repair project for volunteers and trainees offering vital hands-on experience for those wishing to learn new skills and I think the interesting thing and in some ways the beauty of this block is the complete variety of different mortars have been used in it so there's the there's the red mortar as we saw on the other buildings but then here you've got this which is lighter I think the other thing that the interesting thing to look at is that that pointing is sort of untidy really it's sort of smudged across the face of the stone this was a functional building this was a building that was just housing animals and there's quite I like that pragmatism of repair it you know it's just being looked after and the mortar here also has evidence of firing material though so that's bits of coal then it comes to how we reap ointment and although this is quite distinctly different to that there's an honesty to that repair we haven't tried to fake that mortar to look like that minimal intervention is important I think it helps to minimize cost I think it's about identifying those areas that just need gentle nurturing and I think it helps to describe their functionality preserving the character and the history of the building and that's that ongoing gentle repair rather than wholesale improvement or or can be seen as improvement it can be seen as as over improvement over indulging on the building [Music]

Channel: The Landmark Trust

Views: 38,096

Rating: 4.9537039 out of 5

Keywords: wales, conservation, repair, heritage, architecture, lime mortar, restoration, building restoration

Id: j6ke0seIm04

Length: 12min 57sec (777 seconds)

Published: Tue Dec 12 2017