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.

Wrack and ruin, revival and reuse

by Charlie Wellingham

All Souls Church in Bolton was consecrated in 1881, built for local textile mill owners Thomas and Nathaniel Greenhalgh, and is a classic example of the neo-Gothic style fashionable in this period of Victorian England. It was designed by Paley and Austin to dominate the townscape for miles around with its remarkable size, owing to the fact that it was required to seat a congregation of 800 worshippers at maximum occupancy. Sadly the industry that supported the workers of the congregation suffered badly throughout the late-20th century, and by the 1960s the Anglican Church was struggling to support such a large and underused building – finally the church was closed in 1986 and remained derelict for 25 years. An entire generation grew up in the shadows of this local landmark building having never seen its amazing interior.
Conservation 01
The 2014 SPAB Scholars and Fellows were very lucky to visit All Souls Bolton to discuss the ambitious reuse plans that have been developed in partnership by the Churches Conservation Trust and the Heritage Lottery Fund; converting the nave of the church into a mixed-use community centre via the insertion of free-standing ‘pods’ to a contemporary design, whilst retaining the chancel intact for smaller scale Christian worship. The new pods have been devised to respect the original fabric (they do not touch the surrounding walls or ceiling at all), whilst creating a bold counterpoint to the historic building in both form and materiality.

Pods 02
The most significant loss suffered in this adaptation is the removal of the original pews – and it was interesting to debate the impact of this on the character of the church. It clearly has a vast implication on the understanding of the space as it was designed for worship – but as this is agreed to no longer be a realistic future for the building, I would argue that their removal is justified; this one sacrifice paves the way for a new chapter of utility for this structure in the neighbourhood it was built to serve. I am a firm believer in the day-to-day use of our heritage buildings as the most enriching way for us to connect to our culture and history – rather than merely viewing them as an academically or aesthetically interesting artefact of a bygone age. It was fantastic to meet the design and construction teams who share these philosophies, and are working hard to realise them with such ambitious proposals.

Beyond the pods, an incredible team of craftspeople from Lambert & Walker conservation contractors are undertaking a full suite of repair works to ensure the derelict Victorian fabric is fit for 100 more years of service in its new community role. This includes re-laying the slate roof and lead gutters, and extensive conservation of the brick, stone and glass of the elevations in accordance with best practice principles. Alan Gardner, the highly experienced conservation surveyor overseeing the works to the historic fabric, explained to us that the project also sought to maximise the educational and outreach potential that the works could have within Bolton – establishing a sense of ownership within the community that would create true ‘sustainability’ and success. This ranges from open days for the public to technical days for professionals and a number of bursaries for young workers that have evolved into full apprenticeships and potential employment.

Conservation 02
Happily this atmosphere of collaboration and knowledge-sharing meant we Scholars and Fellows were able to muck in and learn some new skills as well! Thanks to Gareth for the joinery instruction, thanks to Ian for the lime mortar pointing guidance, and thanks to James for sharing his amazing stone carving skills. We look forward to visiting the finished project in future to see the local community enjoying their new facilities, and enjoying a new way to appreciate and connect with the built heritage and history that has stood silently amongst them for so long.
Hands On 01