Background:

Rosslyn Castle is a landmark project which offered a unique opportunity for the roofers at B&D Roofing.

The castle, jointly with Rosslyn Chapel, is one of Scotland’s most iconic heritage assets. Surrounded on three sides by the river North Esk, the castle is located within the wooded Roslin Glen, the largest surviving tract of ancient woodland in Midlothian. The oldest parts of the castle date back to the early 14th century and have undergone significant changes over the centuries. However, since the mid-1600s, the A-listed building had been in a partly ruinous state and had been dramatically deteriorating due to exposure to rainfall over the past 350 years.

Before the work, the building was an unusual mix of a ruin and a habitable structure which coexisted within the same building footprint. To safeguard the historic fabric of the building for future generations and create usable spaces, Rosslyn Chapel Trust commissioned architect Page\Park to implement a major £3.5m restoration programme, which looked to re-integrate both elements, while following conservation guidelines.

This work has seen the re-roofing of the East Range to create a permanent roof over the Great Hall and Tower for the first time since 1650. This would sit alongside an extensive programme of conservation and repair works to the building and the repurposing of three layers of medieval vaults below the ground floor to house new air source heat pumps and make the castle Net Zero Ready.

John Dennis & Company (Scotland) Ltd was appointed by the architects as the main contractor, who in turn selected specialist roofing contractor B&D Roofing to carry out the work.

Work began on the castle in the Spring of 2023 and was completed in Spring 2024, with the East Range now operating 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

Roofing product choice:

Through the early stages of the design process, various options for the best approach to conserving and protecting vulnerable masonry were considered through collaboration with Midlothian Council and Historic Environment Scotland. The reintroduction of a permanent roof was favoured as being the most appropriate and future-proof approach, allowing for a more holistic and sustainable project to be undertaken.

AccuRoof, part of SIG Roofing, were involved at the early stages of the project when Specification Manager, James O’Hara, made a CPD presentation to the Architect involved in the scheme. As a result, he was asked to create the H62 natural slating specification, which includes the confirmed pitch, underlay options, headlap dimensions, and fixings required. The One Warranty protection from SIG Roofing was also included in the contract to give essential reassurance and cover.

Whilst the 35° pitch of the existing roof over the East Range could feasibly be matched, this did not translate to the roofing material, which had been Scottish slate. As no newly quarried Scottish slate was available, the project would have had to rely on reclaimed Scottish slate, and the availability of this could not be guaranteed.

The project required a traditional material that was local to help meet its low-carbon objectives. The decision was therefore to use indigenous natural Welsh slate, namely SIGA 120, which is a textured, dark blue/grey slate that is a random diminishing alternative to traditional Scottish slate. It is one of the thickest slates, measuring 7-9mm, and is supplied in blank, random-width, and diminishing-length courses to suit a specific project. Sourced in Wales, it is a great indigenous alternative to Scottish Ballachulish slate and has received approval from Snowdonia National Park. This slate was recommended by James at AccuRoof and supplied by the SIG Roofing branch in Broxburn (west of Edinburgh) for the project.

Roofing products included:

– Welsh SIGA 120 slates (random diminishing courses)

– Douglas Fir timber roof trusses

– Lead sheet for traditional turret work

– Natural wood fibre insulation

Challenges:

There were several key challenges to overcome on this project, all of which were related to the heritage of the building. The Trust asked the architects to design a castle that would be more resilient to climate change, increasingly extreme weather patterns while safeguarding the future of the building.

Preserving the heritage of the building was the driving force behind this project, which required exceptional architectural design, expert craftsmanship and slating knowledge, and meticulous planning to overcome logistical and environmental challenges. During the design process, the architects, in discussion with the council and Historic Environment Scotland, looked at how they could prioritise a conservation-led approach to the project, which would minimise any visual impact on the historic setting whilst bringing the castle up to 21^st-century standards. The architects designed the structure to include a new piece of architecture within the ruin, which has provided a passive solution to the long-term conservation of the ornate carvings. New interiors were designed as legible interventions to the historic fabric, rather than conjecture of the historic form. High-quality natural materials were used that will develop patina over time, just like the original materials of the castle.

One key area of importance was the need to protect the vulnerable masonry with options including 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.

Every roofing intervention demanded precision, from stepped leadwork on the turret to accommodating concealed services through historic flues without damaging fabric. The complexity was further amplified by archaeological considerations and the requirement for reversible, conservation-led solutions throughout. The roof pitch mirrored historic proportions, yet the choice of slate had to reflect heritage aesthetics and low-carbon objectives.

Workmanship:

Being presented with a unique project such as Rosslyn Castle provided an exciting opportunity for the roofing contractors who needed to deliver a high level of skill and attention to detail to ensure the historical elements were sympathetically restored.

Before the contractors arrived on site, the carpenters had installed Douglas fir timber roof trusses and ridge beams, which had been crafted in France. This structure of the roof is exposed internally, and the material was chosen to echo the existing roof construction elsewhere in the building. Due to their weight, it took six carpenters to handle and install the beams.

Prior to delivery, the slates were sorted, graded and holed where necessary as per BS 5534 and BS 8000.  The slates were sorted into different thicknesses and odd slates were set aside for use on eaves or as top slates. The slate is holed from the back, creating a countersunk area that allows for the nail head to sit neatly and increases waterproofing and longevity. The one reliable facet of Scottish weather is rain, and correct installation was critical to ensure the roof remained watertight at all times. 

Installing the traditional leadworks on the turret tower gave the roofing contractors a great opportunity to show their skills on the stepped roof and bossing skills over the timber rolls. B&D Roofing’s master craftsman, Paul Henderson, who began working with lead at the age of 16 and has been in the field for 35 years, showcased his skill through the project. One area of particular note is his work on the lead turret tower which had a re-instated stone work stone spout, an iconic feature that overlooks the castle, and the water pours out to the landscape below. 

Summary:

The overall 2-year project to bring the ruined areas back into use was fully funded by the Rosslyn Chapel Trust and won a Gold Award in the 2025 Scottish Design Awards. It was shortlisted in two categories – conservation and retrofit – and won a Gold Award in the conservation category.

The slate specification team at AccuRoof, were involved in the early stages of this project. Their experienced technical advice greatly assisted, offering relevant product choices for consideration in this restoration scheme. They offer a full service from specification advice to supply, in this case from quarry to roof. Plus a ‘One Warranty’ for up to 75 years. Contact the slate team specifically at https://www.sigaslate.co.uk/about-us/meet-the-team/

Rosslyn Castle by Page Park. Copyright Jim Stephenson 2024