House No 7, Heanish

Introduction

Tiree is the most westerly island of Scotland’s Inner Hebrides; its position, facing the Atlantic with nothing but ocean between its shores and Canada, makes it one of the most windswept places in the British Isles. Remarkably, it is also the sunniest, and its flat and treeless landscape is edged with endless white sand beaches. Tiree’s soil is surprisingly rich and fertile; it is covered with the mineral-rich ‘machair’, a rare type of coastal pasture unique to the Hebrides, with a high shell content. It provides a fertile agricultural base and in the summer breaks out into a carpet of flowers.

On Tiree, as on other Hebridean islands, the traditional dwelling is the ‘black house’, a small, usually single storey dwelling of white painted rubble walls with a steeply pitched roof of thatch, slate or tarred bitumen. The traditional black house is set in a croft, an agricultural smallholding of small fields next to the house. The storage of crops, tools or animals was accommodated in small sheds, often clad with timber or corrugated metal, which were put up alongside the house over the years. Each house and its adjacent outhouses and sheds are separated from neighbouring houses by the small fields of the croft and together they form a scattering of settlements over the 7.8 hectare island. Tiree has about 750 permanent inhabitants.

One of these traditional black houses on Tiree, formerly a listed ruin, has been rebuilt and extended by the architect Murray Kerr of Denizen Works. The site, on the south coast of the island, is accessed by a grass track and enjoys fantastic views of Duin bay to the south and a typical Tiree landward aspect of lightly undulating machair and traditional housing settlements. Like most places on Tiree, the siting of the house is very exposed, with no natural land mass or vegetation to provide shelter from the wind. The new design creates a sheltered enclosure while allowing sun to penetrate and warm the interiors. An array of materials were used including glulam beams for the curved walls, pitch pine and Scottish larch, together with more traditional techniques for the rebuilding of the black house. Inside the house the ceilings and floors are lined with timber, creating warm and gently textured surfaces which reflect traditional interior techniques.

 

Design and layout

The project is designed as a collection of small buildings; the rebuilt house, with single-storey stone rubble walls painted white and a steeply-pitched black tarred roof, is the Guesthouse. Alongside it is the Livinghouse, a new barrel-vaulted structure partly sunk into the ground and clad with sinusoidal galvanised steel sheets and vertical tar-painted boards. Another smaller single-storey barrel-vaulted structure, the Utility block, is a utility room/studio/entrance; it is clad with galvanised steel sheets and corrugated fibre-cement sheets with lead trim.

The three structures are linked together with a small glazed atrium which acts as the main entrance hall. The immediate effect is of a traditional cottage flanked by agricultural buildings, but a closer look reveals a modern and carefully planned design which reflects the complex character and vernacular of island crofts.

From the glazed atrium a short flight of solid timber stairs leads up to the social heart of the new Livinghouse, the living/dining kitchen, a spacious light-filled room roofed with a dramatic timber-boarded barrel-vault and lined with a floor of oiled oak floor boards. Underneath a basement houses master bedroom, bathroom and changing room. The Guesthouse has a bedroom and snug with a woodburning stove on the ground floor, with another bedroom and bathroom within the pitched roof space of the floor above.

The Utility block/studio also leads off the atrium space and includes a laundry space/wet room plus a studio/'Lego' room for painting and play. Heating is provided by an air-source heat pump and by wood-burning stoves in the living room and snug.

 

Construction

The curved shapes of the Livinghouse and Utility block were developed by careful analysis of traditional local vernacular buildings and determined by the constraints of what was could be shipped over in a CalMac ferry. Strong winds and severe exposure conditions were another factor; the frames had to be designed for an overall horizontal wind loading of 1.44KN/m², almost equal to a domestic floor loading (1.50KN/m²).

The Livinghouse and Utility block both have a portal frame structure of CNC-cut spruce glulam beams. The two structures consist of a series of 250 x 56mm curved glulam portal frames at 600mm centres. The roof curve was based on a 3750mm radius, which was the maximum that could be achieved. Each glulam frame was split at the apex into two sections to allow for ease of transport and connection on site. This also allowed the contractors to erect the frame quickly and safely in the inclement weather.

The frames were fixed on site to the concrete floor plate at the base by means of BAT heavy duty angle plates. The floor plate in turn was bolted and strapped to the head of the concrete basement walls with a simple steel plate screwed connection at the head. The glulam frames were then insulated and clad externally.

The curved wall/roof of the Livinghouse is clad with sinusoidal galvanised steel cladding. The curved gable edges to the steel sheets are clad with lead trim, creating a strongly-defined projecting edge which protects the vertical gable walls. The gable walls are clad with tar-painted vertical 150 x 22mm board-on-board cladding of Scottish larch. The curved walls of the upper living/dining/kitchen have large windows which take the form of projecting boxes framed in timber and clad with Code 5 lead sheet.

The smaller Utility block has a shallower curved roof clad with sinusoidal galvanised steel, lined with lead trim at eaves, gables and window flashings. The walls are clad with corrugated fibre-cement sheets, laid horizontally, and the windows are lined with lead flashings.

The Guesthouse was rebuilt with traditional stone rubble walls and an insulated timber frame inner leaf. The roof is constructed using traditional timber frame techniques, with a curved ridge made up of profiled timbers fixed to the tops of the trusses. The Guesthouse is roofed with tarred bitumen roofing felt, torched on and then painted with tar in the traditional way. Like the Livinghouse, the painted timber windows in the pitched roof are clad with lead.

 

Internal finishes

Several different types of pine were used internally. As the architect explains: ‘Pine tongued and grooved boards are traditionally used internally throughout the Highlands and Islands and we decided that using this traditional material in a slightly different way could give us an interesting internal feel while still being relevant to the islands’. The kitchen worktops are made of pitch pine and pine skirting boards are used as the cladding to the ceilings of two of the main spaces. The stairs in the hall which lead to the main rooms were laid like ‘Jenga’ blocks on site after being milled to size from reclaimed Victorian pitch pine beams.

Completion Date:

August 2013

Year Published:

March 2015

Building Type:

Private house

Location:

Heanish, Isle of Tiree, Scotland

Client:

Private

Architect:

Denizen Works

Structural Engineer:

CRA Engineers

Main Contractor:

John MacKinnon Builders

Glulam Timber Structure:

James Donaldson & Sons

Timber Suppliers:

James Donaldson & Sons

Timber Elements:

Glulam wall and roof structure, internal and external cladding, floor boards

Timber Species:

Scottish spruce glulam, Scottish larch, Scottish pine, reclaimed pitch pine

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