The Engine Shed

The Engine Shed is Scotland’s dedicated building conservation centre, based in Stirling. Run by Historic Environment Scotland, it serves as a central hub for building and conservation professionals and the general public.

The Engine Shed is a bit of a mystery. It was built sometime between 1896 and 1913, first appearing on the 1913 Ordnance Survey. Unfortunately, as a military building most of its history has been destroyed or lost. Stirling County Council were keen to see the Engine Shed brought back to life and offering something to local communities and beyond. In 2015, they sold it to Historic Environment Scotland for the bargain price of one pound.

The materials we used in the restoration of the Engine Shed were selected on the basis of three key criteria: sustainability, promoting traditional skills and materials and supporting locally-available materials and manufacturers.

The Engine Shed is a simple yet instantly recognisable building. It is single storey, approximately 11m high, 14m wide and 41m long, with sandstone walls, a slate roof and a clerestory lantern that runs the length of the building.

The high-level clerestory and the raised roof and uninterrupted metal windows give the Engine Shed its iconic shape and character, and we quickly developed a conservation strategy for the clerestory at the beginning of the renovation project. Hand cleaning took five hours per window, as they were cleaned to a SA2.5 standard by a specialist contractor.

We have managed to balance innovation and traditional materials to conserve the character of an old military building whilst improving its environmental impact.

We discovered that the stone the Engine Shed was built from came from two different quarries in North Lanarkshire. However, all the quarries in the area are now closed, which made it quite difficult to find suitable replacement stone.

Large sections of timber were needed for the frames of the two wings of the building. Glulam timber from European Larch was considered the best choice, manufactured from smaller, commercially-available timber sections. 100% of the larch glulam (about 50.03m3) was 100% PEFC certified. All the timber elements were sourced from well-managed forests and/or plantations.

Glulam timber was an energy efficient choice too, as achieving the same structural performance as the glulam in either concrete or steel would have significantly increased the energy cost. Glulam timber is also much lighter than other framing techniques, and resulted in savings in the foundations, construction and transport of the material.

The base of the columns is secured with 6no internally resin threaded rods, eliminating the visual aesthetic of fixings at low level. At high level the frames are connected with industrial galvanized bolts. There are a total of 95 Glulam members on the Engine Shed and 1640 bolts.

The building was designed to be responsive and adaptable, both now and in the future, and the use of a timber portal frame provided a very flexible building. No internal walls are load bearing and we are able to divide spaces within the building to meet all the different needs of our visitors.

By leaving the interior brickwork exposed, we are respecting the skill and materials that went into its construction. However, the gables have both been lined with a clay board, a composite material consisting of clay and lightweight aggregates, including reed matting, straw, hemp and jute fabric, whilst the laboratory walls were finished with clay paint. A base layer of clay plaster and a finishing coat of pigmented clay plaster skim were applied to the clay board.

The new sheds are insulated with 300mm of sheep’s wool insulation packed between the timber JJI Wall and roof structure making the new sheds thermally efficient with a U-Value of 0.11.

The ‘flowcrete’ finished floor is chemically resistant and antimicrobial (so controls most bacteria and fungi which come into contact with floor).

The ceilings in the wings are made from heraboard, a sustainable material made mostly from wood, water and magnesite. The wood is sourced from sustainable Austrian forestry and the board is recyclable and has a lifespan of up to 80 years. These boards have an extremely low impact on the environment and their properties complement the clay board and plaster. By absorbing and reducing background noise and helping regulate humidity and climate, the materials in the ceilings improve visitor wellbeing, concentration, efficiency and performance.

We have taken an old, neglected building and turned it into a modern, healthy, comfortable environment for people to come and learn about their built heritage.

The Engine Shed was 2018 winner of CIAT’s Award for Excellence in Architectural Technology. The Judge’s comments were:

An interesting approach to this historically-significant building. Excellent conservation practice is demonstrated through the use of traditional materials, technology and sustainability to demonstrate the adaption and reuse of a historic building for a new life. Careful consideration of the existing structure with a non-excessive insertion creates an interesting and contemporary space.

The Engine Shed demonstrates how new and traditional materials create not just an aesthetically pleasing environment to champion the crafts and skills required to complete this project but to showcase the applications of technical excellence in Architectural Technology. With sustainability at the heart of the design, the judges were unanimous in their decision that the project is the worthy winner of the 2018 Award for Excellence in Architectural Technology.

This article originally appeared in CIAT’s Architectural Technology Journal, published in Autumn 2018. It was written by Historic Environment Scotland / Reiach & Hall Architects.

--CIAT

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