Coastal House, Devon

Introduction

The practice 6a architects has reconfigured and extended a large early-twentieth century house in Devon. The house itself seemed initially unremarkable but the location is extraordinary; it stands close to the coast with extensive views of the sea and is set in an Area of Outstanding Natural Beauty.

The house had been built with a double pitch slate roof and, it was discovered, massive stone rubble walls, clad with render and on two sides a distinctive Delabole slate to withstand the attrition of sea and wind. It was an important part of the brief to maintain the original external character, but this was both intensified and subtly altered to dramatic effect internally. The original slate cladding and render were removed, all the walls externally insulated and re-clad with a rainscreen of reclaimed Delabole slate tiles.

The door and window joinery was stripped back to the stone openings and dropped below lintels to create elongated 3.7 metre high doorways at ground level and large scale windows, with all new joinery set into the external cladding layer. The eaves have a new cast lead fascia and a new external veranda of green oak wraps around the southern and western elevations of the house, giving sheltered views out to the sea.

Inside the house, all has been transformed. What was a traditional layout of smallish rooms has been reconfigured into a new set of internal volumes, all with clear visual and physical connections between them, at the same time creating new links between the interior and the landscape.

In its original state the house was divided into two parts; a larger two storey and basement on the south side and a lower two-storey extension, probably a later addition to the original building, on the north side. The basement has been removed so that the two ground floor levels are now aligned and the north end of the house has been raised to create an additional storey. The disparate floor levels between these two parts are united by a galleried timber staircase. It rises from the hall at the centre of the house, turning to connect bedrooms and levels, creating open balustrade landings at every stage in its journey upward. It gives views which link the whole house across three axes: across the house from the front door through the dining room to the oak tree beyond, from the back door through the hall and living room to the sea, and from the centre of the hall vertically up to the sky. The staircase is flooded with light from a large glazed rooflight.

The use of timber

The central hall reveals the various floor levels and the exposed primary timber structure, a series of solid, air-dried, sustainably sourced oak beams which span between the original stone walls. Larger structural interventions within the masonry were made with concrete cast in-situ against timber formwork, echoing the timber paneling construction throughout the house. The staircase consists of oak treads and risers supported by 300 x 200mm solid oak stringer beams, exposed to match the oak structure alongside. The balustrades to staircase and landings consist of a curved oak handrail supported by tapered oak spindles which are alternately splayed into the oak beams beneath for rigidity, enabling them to remain slender and maximising light and views through them.

The theme of tapered oak elements is repeated at a different scale in the drawing room. Here, the removal of the basement has increased the room volume and contributed to the tall, elongated external openings of windows and doors beneath original lintels. Internal linings were stripped out and the original stone masonry walls have been revealed, suggesting clues of their previous form. Fireplaces have become wall recesses, former joist supports have become low-level shelving. The window in the west wall of the drawing room is lined with timber shutters and flanked by bookcases backed with panels of vertical boards of FSC-certified tulip wood painted white.

The drawing room ceiling joists and the herring-bone struts between them are exposed and painted white. They are supported by a pair of 375 x 200mm oak beams which are connected with a traditional stop-splayed scarfed joint, secured with 20mm diameter dowels and tightened with oak wedges. The beam is supported in turn by a 4 metre tall tapered oak column.

The timber structure

Daniel Dowek, structural engineer of Price & Myers writes: ‘The new structure is mostly timber with a few visible reinforced concrete elements. Large exposed oak beams and posts with traditional joints are used to support the floors, walls and roofs. The use of long span oak beams has meant that limiting long term creep deflection and moisture movement has been a key design consideration. Specification of well-seasoned oak, together with limits on the strength grade, moisture content and growth ring orientation has been critical.

The central boarded staircase uses oak stringers with elegant splayed balusters dowelled into the top face of the stringers. By bending them slightly in towards the handrail the balusters have been pre-stressed, allowing them to be as slender as possible. A concrete framed opening at the bottom of the staircase leads into the drawing room with an impressive exposed herringbone strutted joisted ceiling. The ceiling spans on to a scarf jointed beam held up by a tall post in the heart of the room.

Wind loads are significant due to the exposed coastal location so the joisted floors are tied to the walls with pattress plates, and the floors and roofs are sheathed with boards or plywood to transfer the lateral loads to the masonry walls. The sequence of works for replacement of the existing floors and removal of the roof boards therefore presented an interesting structural challenge in order to safeguard the stability of the stonework, which is very loosely bedded in a soft lime mortar.

The north end of the house, probably a later extension to the original building, has been raised with an additional storey, with the external stone walls capped with reinforced concrete and then built up in softwood. The existing southern end trussed purlin roof has been retained and extended to cover the new north extension. A consequence of this is that the slopes of the roof in the north of the house no longer marry up with the internal walls and so asymmetric trusses with large oak tie beams have been used.

An external green oak veranda wraps around the south of the house. This features tapered oak posts supporting a shallow oak rafter roof. The veranda is pegged together with mortice and tenon joints and strapped back to the walls of the house for stability. To counter uplift forces, the posts have also been dowelled into their foundations with stainless steel rods’.

Finishes

All internal and external oak was left untreated and an oil treatment was applied to the maple handrail. New windows were fabricated from Accoya and painted white.

Sustainability

Rather than demolishing and rebuilding, the original massive masonry walls have been retained, bringing significant environmental performance benefits. Their mass stabilises internal temperatures while external temperatures fluctuate, keeping the house warmer in winter, and cooler in the hottest summer days. The embodied energy in the original construction is also retained. The whole building is wrapped with 200mm of wood fibre insulation beneath locally-sourced reclaimed slates maintaining the breathability of the whole construction. Solar thermal panels are positioned within the valley of the roof.

Awards

Wood Awards 2017
Arnold Laver Gold Award and Interiors Winner

 

Completion Date:

Spring 2016

Building Type:

House

Location:

Devon

Architect:

6a architects

Structural Engineer:

Price & Myers

Main Contractor / Builder:

JE Stacey

Joinery:

Touch Design Group

Timber Supplier:

Traditional Oak and Timber Co.

Timber Species:

French oak, British Douglas fir, British pine, tulipwood, Accoya

Timber Elements:

Staircase, part roof structure, internal joinery, doors and windows

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