Building Limes Forum

By Declan Cahill
Earlier this year I wrote a blog post on the wonders of lime which outlined a period on the Scholarship where we were beginning to understand the historic use of lime. Since writing that post, we have travelled across most of the UK and met a wide range of people who are involved in the repair and conservation of historic buildings. On saying our thanks and goodbyes, a common question was repeated: “Are you attending the Building Limes Forum in September?” As the conference has now become a well-integrated part of the Fellows’ and Scholars’ programme we were pleased to hear that we would get the chance to catch up with so many people we have met along the way.

BLF Delegates at St. Georges Hall

BLF Delegates at St. Georges Hall

The Building Limes Forum (BLF) is held annually in September and brings together a variety of people from across the UK and further afield for a three day conference on the use of lime in it’s different variations. The conference was held in Liverpool this year and included a programme of presentations, demonstrations and site visits, as well as the annual general meeting of the BLF. I was particularly interested in two topics that were discussed throughout the presentations and demonstrations: hot lime and how our use of naturally hydraulic limes needs to be questioned.

The conference was opened by Stafford Holmes, who presented a talk on “The Delight of Diversity”, giving everyone a reminder of the different geological limestone strata across the UK, and how both earth and lime have played an integral part in the construction of our historic buildings. The first talk on hot lime was given by Roger Curtis, technical research manager at Historic Environment Scotland (HES). He gave an insight into the research being lead by HES into hot lime mortars. I think it is important here to include Roger’s definition of hot lime in their research, that is “quicklime, being mixed on site with aggregates, often gauged. Using a traditional additive (or pozzolan) where necessary, using the material warm, cool or mature and for building, pointing or harling purposes.” Roger gave an overview of the past and current research being undertaken and the four studies that are due to be published in Spring 2017, these being:

Historic Examples of Hot Lime – Tom Addyman
Recent Examples – Craig Frew and Bill Revie
Historic text Extraction – Nigel Copsey
Consideration in the specification of Hot Mixed Mortars – Ros Artis

There is also going to be a database set up for the analysis of lime mortars. This was fully introduced by Anne Schmidt later in the conference. Roger also highlighted that there will be a hot mixed lime mortars seminar in December 2016

Triona mixing lime mortars at Duart Castle

Triona mixing lime mortars at Duart Castle

Roger’s talk lead nicely into a presentation by Nigel Copsey on his research of old texts on lime mortars. His research has highlighted how earth and lime have historically been used in tandem with one another, and how historically mortars would be mixed hot, most commonly using the common or ordinary method of mixing. Roger’s analysis has covered the continent and has included texts from France and Spain that had never previously been translated.

On the Saturday, the conference covered current research into hot lime by Alison Henry of Historic England and the development of mixes for exposed historic buildings by Lucie Fusade at the University of Bath. Cristiano Figueiredo, also of the University of Bath, presented his analysis on how fit for purpose BS – 459-1:2015 is in a conservation context. Sarah Scammel, another speaker from University of Bath, presented her research into the impact of calcite aggregates on the properties of air lime mortars. All of the talks were deeply insightful but have pointed towards how we are under-using quicklime and overusing natural hydraulic limes without really understanding their strengths and properties, and what boundaries the British Standard gives. This research will hopefully further our understanding of lime mortars in their different states and how they act with historic building fabric.

Mixing quicklime using the common or ordinary method

Mixing quicklime using the common or ordinary method

Sunday morning of the conference gave an overview of the various activities of building limes forums around the globe, as well as introducing next years location for the conference, Trondheim Cathedral, Norway between 7-10 September 2017.

The presentations of the conference were closed by David Wiggins, a structural engineer who has researched into lime mortar and sacrificial weathering. David covered the primary decay drivers of lime mortar, frost attack and salt crystallisation, and how the pointing mortar is a functioning aspect of solid masonry construction, actively removing moisture and salts from the wall. Crucial to the pointing mortar’s function is the free lime content that makes the mortars sacrificial. This is something that natural hydraulic limes do not have but a hot mix produces a mortar with a high free lime content.

The conference was a great weekend to learn about the current research and practise that is ongoing and being applied in the effort to repair and conserve our historic buildings. On behalf of the Scholars and Fellows, I would like to thank the Rathbone Foundation for funding the bursary that allowed us to attend the conference and hope that they will continue to support the Scholarship and Fellowship programmes in the future.

More information about the BLF, the 2017 conference and the upcoming Hot Mixed Lime Mortars Seminar & Workshop on 20 October.

Scholars head north

by Gethin Harvey

Vernacular Buildings
Since the last post, the Scholars have headed north to Cumbria and into Scotland to study the effect of changing geology and wetter climates on vernacular buildings and the accompanying variations in construction techniques.

Solid earth wall construction

In such areas the detrimental effects of water ingress and damp can be exacerbated if not addressed; with increases in average annual rainfall over recent years, it also poses questions on how well equipped historic buildings are to deal with the amount of rainfall seen today and associated repair philosophies.

One vernacular tradition is the construction of buildings with solid earth wall structures which go by different names dependent on the regional variations in construction and local dialect. These are known locally in Cumbria as ‘clay dabbins’ and following a guided tour of Burgh by Sands by 2014 fellow Alex Gibbons it became apparent that they are often difficult to spot, hidden behind protective lime renders.

This not only leads to uncertainty in the exact amount surviving in the UK it also means that they may often not have the statutory protection they deserve. We subsequently joined local craftspeople and volunteers to progress the construction of a newbuild clay dabbin building in the RSPB sanctuary on the Solway Plain. The experience of working with the material revealed the practicalities which determine the methodology of construction; the walls are formed of lifts only a few inches in height, contrasting with, for instance, cob buildings in Devon where the drier material allows lifts of up to 2 ft. It was a great example of how traditional crafts may be used to provide sustainable opportunities for building using nothing outside the immediate context of a site. Surviving examples serve as great precedents for this and their maintenance is crucial, one of many topics which will be covered at Clay Fest 2016 which will provide opportunities for further explanation and hands-on experience at the RSPB Campfield Marsh Reserve in Bowness-on-Solway, Cumbria on 18 – 23 July 2016.

For more information please see the Earth Buildings UK website.

Scottish Working Party

Balmerino Abbey, Scotland Working Party

Despite predictions of thunderstorms, the weather was glorious (with a minor exception – the typically soggy British BBQ on the final evening).

The weather enabled the volunteers to throw themselves into the work at Balmerino Abbey, a ruinous masonry structure in Fife. This included raking out cement pointing in a boundary wall and repointing with lime mortar; soft capping trials and preparing the materials for repointing and soft capping.

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Lime has been a constant theme throughout our visits and it was a great asset to have Bill Revie, Andy Bradley and Duncan Strachan from the British Limes Forum to guide us. For the lime pointing a hybrid mix of quicklime gauged with NHL 5 was used with local sharp sand. This was a combination we had not previously seen and was designed to provide an initial chemical set to prevent the mortar being damaged by frost and/or wind before carbonation. Their interactive demonstration of the lime cycle and the ‘3-minute kiln’ (for construction, not burning!) was of great benefit to all present and provided us with a better understanding of its use in more severe climates.

Kiln at Scottish Working Party

With a similar range of repair methods as those proposed for the SPAB England Working Party which will be held at Greatham, Hampshire on 3 – 9 July 2016, it was great to have the experience of Alison Davie Construction Ltd to supervise the works. Aside from the practical experience it was a brilliant social meeting with many partaking in their first official ceilidh and we would like to convey our thanks to Historic Environment Scotland and National Trust for Scotland and all others involved in an incredible few days.

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The wonders of lime

By Declan Cahill

Since the last blog post the Scholars have spent two weeks in North Wales, a week on the SPAB’s bi-annual repair of old buildings course and a week in Somerset, the last four weeks have seen a focus on lime, both intentionally and unintentionally. Prior to the Scholarship, my involvement with the use of lime was project based, and my understanding of the historic use and characteristics of the material was fairly rudimentary. I thought I had a grasp on the different types of lime, however I still found myself questioning what I was specifying, the worry that seemed to hang over me was whether I was going to cause more damage through specifying a lime mortar that wasn’t cohesive with the existing building. After the last four weeks, I believe my apprehension was totally justified.

Plas Tirion, North Wales

Plas Tirion

Plas Tirion sits in the Conwy valley, and is home to the Natural Building Centre (NBC), we spent the day with Ned Scharer (owner of the NBC), who showed us how his use of lime to repair Plas Tirion underlies their philosophy of specifying the appropriate material for the location and the part of the building it is being used on. Therefore an understanding of the history of the building and its materials as well as an appreciation of the impact the weather has on these materials needs to sit at the beginning of the discussion regarding which is the correct lime to use when carrying out repair works. Knowing of our forthcoming trip to Italy, Ned was also able to introduce us to the art of fresco painting and gave us the opportunity to have a go ourselves.

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Declan and Gethin trying fresco painting

The rest of this week was spent with Elgan Jones, an architect of Purcell and 2014 Scholar, and Elinor Gray Williams of Donald Insall Associates, a Scholar from 2006. Site visits over the three days included both the grandness of castles of North Wales as well as more modest vernacular buildings and churches. We visited St. Cwyfan Church which was repaired in 2005 by Ned Scharer and included the use of broken shells and saltwater in the mortar mix and limewashes respectively. Read more about the limework at St Cwyfan’s Church-in-the-sea.

In the heart of the Brecon Beacons, the historic farm of Ty Mawr is the home of Nigel and Joyce Gervis, and Ty Mawr Lime Ltd. The visit to Ty Mawr helped us understand their involvement in the resurrection of the use of lime in historic buildings since the company was founded in 1995.

Scholars and fellows with Stafford Holmes and the line kiln at CAT

Scholars and Fellows with Stafford Holmes and the lime kiln CAT

We then met up with the Fellows and Stafford Holmes to spend five days at the Centre of Alternative Technology (CAT) at Machlynlleth. The aim of our time at CAT was to carry out some maintenance works to the lime kiln, further our knowledge of lime and its uses, and to finally fire up the lime kiln to burn and slake lime. Our time with Stafford gave an insight into the wide range of uses of lime, and started to decipher how to approach the use of lime in conjunction with historic buildings. Stafford was able to teach us about the different types of lime and their appropriateness in different contexts, and by getting first hand experience of what is required in order to burn and slake lime has really helped me to understand the extensive and traditional use of lime in historic buildings. We also made a site visit to Portmeirion, which sparked interesting debate regarding pastiche and the relocation of historic buildings.

Scholars and fellows at Portmeirion

Scholars and Fellows in Portmeirion

The five day repair of old buildings course consists of three days of lectures and two days of site visits. I cannot start to communicate the amount of information that is gained through attending the course, but I can say that it is an extremely useful starting point for those involved in conservation of historic buildings. The lectures on the various aspects of historic building fabric are given by experts in their individual field, and the two days of site visits allow you to see how this is put into practice. The spring course this year included site visits to the Queens House at Greenwich, the longest medieval barn at Frindsbury, Knole House in Kent and St. Mary’s Church and Hadlow Tower at Hadlow.

During National Mills Weekend I volunteered at Bradwell Mill just north of Milton Keynes. National Mills weekend is arranged every year to open up the windmills and watermills of the country to the general public. This year the William Morris Craft Fellowship Trust led a weekend of demonstrations and fundraising at Charlecote Mill. This helped raise £930 for the Trust.

We then headed down to Somerset where we spent time with Jo Hibbert, Scholar from 2002, who showed us a variety of projects she has been working on, including defence posts in Plymouth. We were also lucky enough to visit Carpentry Oak in Totnes and try our hand at stone carving with Westcountry Stonemasons in Ivybridge. Following our time with Jo we then spent a great day with Shaun from Somerset Stone Conservation, this allowed us to get some more hands on experience through helping to consolidate and re-point a railing plinth. An information-packed day was then spent with Philip Hughes, who was the first building surveyor scholar and is the current chairman of the SPAB technical panel. We visited projects at St. Lukes Pastoral Church in Wincanton, as well as the ongoing works at Wimborne St. Giles, which has been praised for its various approaches to conservation.

We finished the week and the last four weeks of the Scholarship at Woburn Abbey, where we were given a tour of the abbey by the curator, Matthew Hirst, and were able to have a look at the works being administered by Nick Cox Associates. The visit was also used to discuss our ideas for the Plunkett part of the Scholarship where we will spend the last three months of the programme visiting country houses to study a research topic of our choice.

Past Scholars and Fellows: Where are they now?

In June we met up with Gail Haddow, 2007 Fellow and plasterer, onsite at Pound Farm, Midhurst. Gail has her own lime plasterwork and historic building repair business, Earth and Lime Ltd.

S&F_Gail HaddowGail began along her chosen path purely by accident, she says. She started out in landscaping and horticulture and she just knew that she couldn’t work in an office. Gail says ‘I always had my hands in the dirt somewhere!’

Whilst working for St Blaise Ltd Repair & Conservation of Historic Buildings in the late 1990s, Gail began cleaning stone monuments, and carrying out small repairs to decorative plaster work and water damaged ceilings. Gail credits St Blaise with kick-starting her passion for lime; there she was able to take on larger plastering jobs. When she started out most colleges didn’t offer training in lime, she says, so she learned on the job.

The Fellowship supplemented her hands-on lime training and offered Gail more of what she loved about working with historic buildings, the opportunity to enjoy parts of buildings that the public don’t often get to see.

Looking back on the six month country-wide tour, Gail says the Fellowship gave her a huge confidence boost. An integral part of the Fellowship is collaboration and camaraderie, to have your opinions challenged by the other Fellows and Scholars in a supportive environment. The site visit that really stuck with Gail was Chapter House in York Minster and climbing up through the building’s amazing timber frame roof.

Since the Fellowship, Gail has worked across England from Hereford to Hampshire to North Wales. Gail says that a plasterer gets to know the local material, ‘you get used to the way that your local sands behave with lime, you know what you can and can’t get away with! Going to a new area, you definitely have to re-learn a lot of that’. Gail has a very refreshing approach to her work and says that ‘it always seems that Mother Nature gives you exactly what you need to build with, wherever you are’.

Gail is currently working on the plaster repairs at Pound Farm, a 15th century building with 17th century and late-Victorian additions. During the tour of the site, Gail was keen to point out the smoke-blackened wattle and daub cross frame with woven hazel rods. Up in the roof space, Gail enthused about the 15th beams, ‘Here you can tell that the craftsman working on this beam had a ding in his axe, it has marked the wood in a unique way, I can tell exactly what beams he worked on’. The Fellowship fosters this love of craftsmanship and the place it has in protecting our heritage.

Cottage Conservation

by Conor Meehan

On Thursday the group re-joined Jo Hibbert to visit a nearby cottage where she and her husband Ed, a joiner, were working alongside the enthusiastic home owners. All parties rolled up their sleeves to muck in; Tyrone showed the Scholars how to “boss” and “dress” some lead for the house drainage valleys. It wasn’t long before Ross and Hannah were up on the roof installing the shaped lead under Tyrone’s watchful eye. Richard and Conor helped Ed erect his crafted green oak framework for the newly designed porch. Mortises, tenons and dowels were integral to the framework design, not a nail or screw in sight.

The homeowners were conservation enthusiasts and were experienced in the use of local materials – so much so, that both the Scholars and Fellow were soon mixing mortar from lime, locally sourced clay and straw reaped from the field next door, and throwing it up on the exposed interior stonework. Spending the day working on a small project where everyone involved could call upon recent teachings and contribute was really rewarding.

Pole Chapel in Colyton Church The week finished with a visit to the Pole Chapel in Colyton Church where Jo Hibbert and Torquil McNeilage, 1992 Fellow, discussed the damage associated with major moisture infiltration to the 16th century chapel and the sculptured memorial monuments.

Everyone thoroughly enjoyed their week in Devon and Somerset, the hands-on experience of different conservation disciplines was invaluable. The group had the chance to learn from master craftspeople, including Fellow leadworker and patient tutor, Tyrone. The West Country sunshine and homemade cider made it all the sweeter.

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Getting our hands dirty

There’s no better way to learn than through practical experience, and one of the many perks of the SPAB Scholarship is that we get to try our hand at everything! Here’s just a few things that the ever-enthusiastic Henry has been turning his hand to over the last few weeks.

Henry tackles the drains with Nick Warns at Swaffham Church, Norfolk

It’s hardly glamorous but the regular maintenance of gutters and drains is often the first step in keeping an old building in good shape, especially as the British Summer weather is being true to form! As William Morris advised ‘stave off decay by daily care’. You can find advice and tips on basic maintenance by visiting our sister site Maintain Your Building.

SPAB Fellow Sam shows us the ropes at her workshop with Simon Armstrong at Wells Cathedral Masons

An important part of the Scholarship and Fellowship scheme is that Conservation professionals and craftsmen travel and work with each other, giving them an insight into the others’ practice and respect to last a lifetime of working together to help old buildings. This was a great chance for us to see Sam, and award-winning stonemason, at work on her home territory, the glorious Cathedral of Wells.

Henry has a go at Thatching with Tom Dunbar, of Dunbar & Bunce Master Thatchers.

A great chance to learn from Tom, who completed the SPAB Fellowship in 1999 and is the only thatcher so far to be a SPAB Fellow!

Stafford Holmes (co-author of ‘Building with Lime) imparts his knowledge of Lime at CAT

Henry just can’t stop working! Some time well spent at the Centre for Alternative Technology, an education and visitor centre which demonstrates practical solutions for sustainability, set in the heart of Wales.