Rosslyn Castle

A once in a generation project

Rosslyn Castle, jointly with Rosslyn Chapel, is one of the most significant heritage assets in Midlothian. Surrounded on three sides by the river North Esk, the Castle is located within the magnificent wooded Roslin Glen, the largest surviving tract of ancient woodland in Midlothian.

The A-listed building known as the East Range, which dates back to the 16^th century, has remained partly ruinous since the mid-1600s. The project provides a new permanent roof over ruinous areas of the East Range for the first time in over 350 years, bringing the spaces back into use and safeguarding the historic fabric for future generations. Along with an extensive programme of conservation and repair works to the building, three layers of medieval vaults below the ground floor have also been repurposed, now housing new air source heat pumps making the castle Net Zero Ready.

The project was fully funded by the Rosslyn chapel Trust, a charity established in 1995 by the current Earl of Rosslyn. The Rosslyn Chapel Trust oversee the full Rosslyn precinct and are responsible for the care and maintenance of the various buildings on the estate.

The Rosslyn Chapel Trust commissioned Page\Park to implement their vision to conserve the Great Hall, adjoining tower area, and the three layers of medieval vaults below, which were dramatically deteriorating due to their exposure to rainfall for the past 350 years. The East Range operates as a holiday let in partnership with the Landmark Trust and income generated from the holiday accommodation is used to help look after the full castle complex.

Architectural Concept

The A-listed building known as the East Range dates back to the 16^th century and sits within a Scheduled Monument covering the surrounding areas. Overall the aim of the project was to carry out a comprehensive scheme of conservation works, making it more resilient in the context of climate change and increased rainfall having been partly ruinous from the mid-1600s. This was achieved through a new permanent roof over previously ruinous areas of the East Range, covering and protecting these areas along with highly significant carvings inside for the first time in over 350 years.

The decision to reroof the castle was born out of a conservation management plan Page\Park undertook for the entire area, with one of the primary outcomes being to aid not only the long term management of the castle but also its setting. The conservation-led approach to the project sought to minimise any visual impact on the historic setting whilst upgrading the castle and bringing it up to 21^st century standards.

Through the early stages of the design process, various options for the best approach to conserving and protecting the vulnerable masonry were considered through collaboration with the council and Historic Environment Scotland. Options included conservation of wall heads only, light-weight structures, and the reintroduction of a permanent roof. The latter option was agreed as being the most appropriate and future-proof approach, allowing for a more holistic and sustainable project to be undertaken. A key aspect of the client brief was to ensure the new and old spaces were well heated, creating a more comfortable holiday accommodation where the 17th century and modern living experiences can harmoniously coexist.

Externally new elements were designed to subtly blend in with the existing form and be sympathetic to the existing materials, despite being purposefully distinguishable from the historic fabric on close inspection. The structure of the roof is expressed internally through exposed douglas fir rafters and linings, which echo the existing roof construction elsewhere in the building. Hidden from view on arrival, on the west gable, new curtain wall glazing juxtaposes the existing stonework with a modern intervention, opening up views to the ancient woodlands surrounding the castle. From the surrounding Glen below, the new glazing offers a glimpse of a new stone fireplace used to conceal structural supports for the new roof and introduce a new focal point in the ‘Great Hall’.

New interiors were designed to be contemporary and not as a reconstruction of the historic interiors, with high quality natural materials used throughout to age well and develop patina over time. An exciting aspect of the project was the level of craft involved, to create bespoke designed elements which complement the rich palette of materials while emphasising existing masonry carvings of exceptional significance.

We are delighted to see this major and innovative project reach its conclusion. This ‘once in a generation’ work will help to conserve the East Range of Rosslyn Castle for future generations to appreciate and will absolutely transform the quality of the experience for guests staying here. ”

Ian Gardner
Director of Rosslyn Chapel Trust

Sustainability

An important part of the project is the addition of new air source heat pumps located within the medieval vaults, making the castle Net Zero Ready. These vaults date back to the 16^th century, meaning it is possibly the oldest building in the world to have adopted air source heat pumps as a sustainable, low carbon technology. Historically used as service spaces, the vaults provided kitchens, bakehouses, and dungeons, these spaces are now revived once more as modern-day service spaces operating as plant rooms.

The cutting-edge heat pump technology and historic stone vaults co-exist in a symbiotic relationship, both benefitting from each other, with the thermal mass on the masonry maintaining a consistent temperature within the vaults, maximising the heat pumps efficiency. This makes the Rosslyn Castles sustainable heating system unique when compared with conventional air source heat pump installations. Air movement is also aided by the heat pumps and plant, which helps dry out the masonry, justifying the radical positioning of this innovative technology. To help maximise the efficiency of the heat pumps and to provide resilience to the system, thermal stores have been provided as part of the design, acting as thermal batteries being charged by the heat pumps. By incorporating the thermal stores, it was possible to reduce the capacity of the heat pumps to work within the confines of the available electrical supply, which also aims to lower energy bills for the client.

Combined, the measures are predicted to reduce the building’s heating & hot water energy consumption by 67% and save over 17 tonnes of CO2 per annum.

The upfront embodied carbon (A1-A5) has been estimated to be 174 kg CO2e/m2. Confirmed through post completion Life cycle assessment (LCA) software OneClick.

What has been achieved is truly remarkable and will be forever recognised as a significant and glorious episode in the history of this beautiful building.”

Peter St.Clair
Earl of Rosslyn

What has been achieved is truly remarkable and will be forever recognised as a significant and glorious episode in the history of this beautiful building.”

Peter St.Clair
Earl of Rosslyn

Conservation

The primary aim of the project was to make the castle more resilient in the context of climate change and increasingly extreme weather patterns, achieved through a comprehensive scheme of conservation works. Every intervention was carefully considered and backed by a forensic level of research into the building and history of the site. A common starting point for the practice on all projects ensuring we have a thorough understanding of the building, and the most appropriate approach to protect any significant fabric.

The work strikes a delicate balance between maintaining the overall character of the ruinous building while improving the performance of the external skin. Through research we identified the castle was more than likely harled given its age and location. However, no evidence of harling was found in historic illustrations or text, and the decision was taken to avoid any conjecture and maintain the current appearance of the exterior. Best practice principles were followed for all fabric works, adopting traditional materials and techniques where suitable, confirmed through petrographic and lime analysis. Along with minimising the use of new materials on site. maintaining and reusing as much of the existing fabric as possible.

Masonry Works

An extensive masonry package of works was carried out across the building, particularly focused on the ruinous areas. Due to their exposure from above for centuries, the vaults were in an extremely poor and structurally unstable condition, requiring clearance and consolidation works throughout and the partial rebuild of a highly eroded and poorly rebuilt section of vault that sits below the new livingroom.

Ecology & Archaeology

Numerous challenges arose throughout the project, requiring an innovative approach from all parties involved. The main challenges derived from the location and historic woodland setting. Great care was needed from delivering materials to implementing new services. Along with the extensive ecological constraints, the layered nature of the castle introduced a lot of archaeological challenges.

History

Rosslyn Castle Engraving - T. Hearne (1779)

Rosslyn Castle has been the seat of the St. Clair family since the 12^th century, one of the most prominent noble families in Scotland since the 12^th century. The complex, large portions of which are still visible today, has expanded over time as generations of St. Clairs have added to it.

The family were granted the Barony of Rosslyn in 1070 by King Malcolm Canmore. The present Rosslyn Castle is likely a second iteration of the castle; an earlier structure is thought to have existed in the 12th century, although its location is unknown.

The castle was constructed by William St. Clair during the 14^th century, and largely developed over the 15^th and 16^th century. It has endured multiple major historical events, surviving two significant attacks, first by the Earl of Hertford in 1544 as part of the ‘rough wooing’ (an attempt by Henry VIII to force a marriage between his infant son and Mary Queen of Scots), which led to a period of rebuilding – this was when the East Range was constructed. It was during this time the ‘Great Hall’ was also built, originally around 17m long and 7m wide. The castle was attacked again in 1650 by Cromwell’s army led by General Monk. Tragically, this later attack was so severe it left the castle in a state of ruin from which it never fully recovered. Only the East Range escaped relatively unharmed, although it is thought that it was at this time that the roof over the Great Hall was lost.

Efforts to maintain the castle through the 17th century were focussed on preventing further deterioration rather than active repair. This led to alterations such as the construction of a wall through the centre of the former Great Hall. Despite efforts to repair the castle during the 18th century, the family never had the funds to properly restore the site to a habitable home. By the end of the century, the estate had been divided up and spaces were rented out to a number of tenants. By this time, the site had become popular as a pilgrimage for artists, such as JMW Turner and Hugh Williams, with various artworks from that time depicted the building as a romantic ruin. The castle further deteriorated during the late 19th and early 20th century, although the mid-20th century seen a resurgence of visitors to the estate.

The lack of a dedicated caretaker in the early 1980s resulted in further vandalism and deterioration. This prompted the Seventh Earl of Rosslyn, and current steward, to instigate major repairs and renovations in the mid 1980s. In 1985, the former living space within the castle was converted to holiday let accommodation, operating in partnership with the Landmark Trust, with a larger project of restoration completed in 1987.

Genealogie of the Saintclares of Rosslyn -Father Augustine Hay (1822)

Whole Life Carbon

The project addressed significant amounts of fabric deterioration externally and internally, these upgrades also improved the energy efficiency of the building, a vital element in the successful installation and operation of the new heating strategy. A fabric first approach was taken to improve the energy efficiency of the building through upgrades to the existing fabric where possible. Although heavily restricted due to the significant fabric, insulation was introduced at roof and floor level using natural wood fibre products. Walls were also insulated in areas with wood fibre and innovative insulating plaster products to reduce the buildings heat loss as much as possible without negatively impacting on the extremely significant existing fabric. A new limecrete slab system has been used in new areas as a low carbon alternative to a more typical concrete slab, the use of lime products throughout generally also provides a more sympathetic approach alongside the historic fabric. The limecrete slab build up includes a high-performance recycled glass aggregate insulation layer, made from entirely recycled glass it boasts a very low embodied carbon profile.

The wide range of insulation products were specifically chosen for their breathable attributes and low embodied carbon credentials, and will help deliver substantially lower operational and embodied carbon emissions. The project adopted whole life carbon principles, and was designed to ensure longevity of materials and structure. The majority of the structure is solid masonry construction, an inherently low carbon approach when compared to steel or concrete. New stone was kept to an absolute minimum, reusing as much existing material as possible. Any stone found on the site or salvaged from downtakings was reviewed and catalogued for reuse, being used as new facing stone in walls and floors, to filling the rubble cores of the 1.5m thick walls and even sections of a rebuilt vault. New stone was also sourced from local quarries, reducing transport distances and the carbon footprint of the construction process.

New Roof Buildup - Natural Woodfibre Insulation

New Floor Buildup - Recycled Glass Aggregate Floor Insulation

We relied heavily on the extensive research carried out to identify where a more conservative approach was needed in terms of insulating and installing new services. With a forensic understanding of the existing building, we were able to identify existing flues and voids to conceal and house various bits of plant/equipment which helped minimise physical and visual impacts on the existing fabric and spaces throughout the castle. Existing chimney flues which run the entire height of the building act as service risers from the plant rooms to the upper rooms, completely invisible to occupants and keeping penetrations to an absolute minimum to preserve the existing fabric.

Existing Section Drawing

Fabric Works

Before - South Elevation

After - South Elevation

The majority of the masonry works are focused on the 1.5-metre thick solid masonry external walls, where the erosion was at its worst. To support the new roof structure above, large portions of the walls have been downtaken to a stable core, and rebuilt back up. Repair and rebuilding works were again backed by an in depth understanding of the existing building, examining stone by stone to ensure the delicate balance between old and new was achieved, and repaired using traditional methods such as hot mix lime mortar. Although identified through analysis of the existing fabric, this method was only agreed on through consultation with the skilled stonemason subcontractors, who had extensive experience working with hot mix, which is important as incorrect application can cause substantial defects.

Masonry Works - Repairs to the External Walls

Masonry Works - Restoring 1.5 Metre Thick Walls

Vault rebuilding sequence under scaffold canopy erected during works

Clearance of vault area below new livingroom before works

Vault being rebuilt from above

Ecological and Archaeological Challenges

Ancient Yew Tree and Castle

The biodiversity of the site is also of great importance, being surrounded by a dense protected woodland. Extreme care has been employed throughout the design and delivery stages to ensure the woodlands were maintained, primarily the ancient, approximately 800 year old, yew tree immediately adjacent to the castle. As the project would impact on the woodlands prominent population of protected bat and bird species roost/nest areas, the lowest level of the vaults has been left as found and open to the outside, allowing the wildlife of the woodlands to inhabit the space.

New incoming services and a new drainage treatment system located to the north of the East Range sat in the historic courtyard of the castle, which has long been covered by overburden with self-seeded trees and vegetation. Trenches and service routes were designed to take advantage of previously disturbed routes, but as limited trial pits were restricted beforehand, archaeological deposits were consistently found during excavation. This required an extremely flexible and iterative approach, redesigning the service routes multiple times requiring intricate engineering solutions. A key aspect of this was working closely with Historic Environment Scotland to ensure the Scheduled Monument areas were protected at all costs.

Existing masonry internal structures uncovered during works

The finds were not limited to the external areas, and the need to rebuild one of the vaults required extensive archaeological works internally as well as externally. Various stone structures and remnants of historical features were found during these works, which again required an agile attitude, and innovative response from the Design Team and contractors to maintain the existing masonry where possible.

Project Info

Overview

Client
Rosslyn Chapel Trust

Location
Roslin, Midlothian

Value
£3.5 million

Completion
July 2024

Services

Conservation
Architecture
Interiors

Consultants

Structural Engineer
Narro Associates

M&E Engineer
Harley Haddow

Cost Consultant
Morham + Brotchie Partnership

Contractor
John Dennis (Scotland)

Press

Herald Newspaper

Scotsman Newspaper