The Find
Cotswolds, UK

Located in an area of outstanding natural beauty in the Cotswolds, this hidden 16 acre site reached down a track through a Beech wood provided an unique opportunity to create an exceptional project.  On site there was an existing gamekeeper’s cottage in a very bad state of repair and estimated to date from the early 1800’s. During the initial pre-application meetings English Heritage were consulted and the cottage was Listed Grade II.

As architects for a listed building in the Cotswolds Found Associates looked at the site strategically, seeing the topography of the land and the dilapidated outbuildings as an opportunity to carve a large extension into the hillside.

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Concept Design

The landscape and vernacular stone construction of the Cotswold’s were the main inspiration for the design, which was conceived as a series of dry stone field walls which descend down the slope of the land behind the cottage, articulating the new building into three sections; the entrance and link to the cottage at the same floor level, a lower section to the West housing the main living areas, and a raised wing to the East set further back into the slope which provides the more private spaces of the bedroom accommodation. The roof is the fourth elevation, as the building only emerges from the ground on three sides. Two 15m long rooflights emerge from the slope of the ground providing natural light to the circulation spaces at the back of the building. All of the habitable rooms have a view of the landscape, and are situated on the path of the sun- the bedrooms receiving the morning sunlight and the living space sunlight during the day and the setting of the sun in the evening.

The roof of the first two sections is a planted ‘green’ roof and reads as a continuation of the natural landscape of the site.

The use of the same local stone as the cottage is handled in a different and contemporary manner. The stone is dry wall construction concealing a heavily insulated inner fair faced concrete shell.

Planning and Listed Building consent

At first a new building set apart from the cottage was considered, but the local planning officers were adamant that they would not support an application for this even under the PPS7 planning policy advocating permissions for new country houses of exceptional architectural merit.

The planning and conservation officers were also not keen on the cottage being altered or adapted at all arguing that if an extension was permissible it should be subordinate in size to the cottage, however after a number of meetings, and after being shown a large scale model of an extension where the new structure was set behind the cottage and into the slope of the landscape and clad with a local stone, they began to get excited and supportive of the scheme and planning and listed building consent was finally obtained in October 2007.

The Cotswolds Listed building consent included the following statement:

On paper this proposal appears to be refusable.  The extension is large and seems to contradict paragraphs C7 and 3.13.  However, plans and models cannot completely convey the topography of the site that will, for the most part, mean that the two new ‘wings’ will not be seen together, nor can the plans impart the sleekness of the expanses of glass, tempered only by traditional Cotswold stone walls.

Whilst it will dramatically change the naturalistic and leafy setting of the Listed building, the extension’s modern design, its recessive positioning, naturalistic stone walling, which will appear as terraces of dry stone retaining walls, and the glazing that will bounce back the reflection of the trees opposite, will make the building striking in the landscape, providing a bold and unequivocal contract to the cottage, rather than causing actual harm.

Construction Methodology and Sustainability

The site for the project is designated as an area of outstanding natural beauty, and sustainability was always a key factor in the design process.

This is reflected in the initial concept of integrating the new building into the natural contours of the landscape, covering 2/3 of the roof with soil and planting and to reduce the massing of the building to relate well to the small scale of the original cottage. At the same time as reducing the scale of the new structure it benefits from the increased insulation of the earth. The layout and sequence of spaces follows the path of the sun to reduce lighting costs and to benefit from passive solar gain.

The fair-faced concrete shell provides a great deal of thermal mass to keep the building cool during summers and warm during the winter.

Cross ventilation is employed to cool the building passively, and the tall vertical circulation spaces at the rear of the plan set deep into the hill have ventilation fans to pull warm air out of the building that accumulates via the stack effect.

Cellular recycled glass insulation was employed as floor, roof and wall insulation for its high loading capabilities, its high percentage of recyclable material and zero ODP as well as integral resistance to moisture. It is more difficult to detail an externally insulated building generally, keeping the insulation uninterrupted through all junctions, but the advantages of this method for the building were obvious. Thermally broken reinforcement solutions were employed where concrete slabs span between internal and external spaces, and all of the concrete upstands on the roof structure were thermally broken.

The use of in-situ concrete from a local source reduces the environmental impact of the building. The mix of concrete uses GGBS to reduce the embodied CO2 of the material. The fair faced finish allows the use of thermal mass, and negates the requirement for plasterboard, firrings, claddings etc to provide finishes over the structure. Use of local Cotswold stone both visually integrates the new building into the local landscape, relates to the cottage, and local labour and suppliers were employed to install.

Ground source heat pumps were considered along with water source (there are 2 fishponds on the site that were previously part of the grounds of Prinknash Monastery), but were rejected in favour of air source heat pump units, partly due to the unknown effect of the wildlife in the ponds, and the need to excavate a very large area of the field.

There is a whole house ventilation system with heat recovery installed. The air source units can run on reverse cycle to provide cooling during the hottest days of the year.

Perforated aluminium roller shutters are fitted to the bedrooms outside the glazing so the large sliding glass doors can be fully retracted into pockets in the wall at night to provide secure natural ventilation. Likewise during hot summer days the shutters can be lowered to keep the bedrooms cool, by reducing thermal gain.

The historic cottage was also restored as part of the project, using natural materials like sheepwool insulation in the roof space, and lime pointing to the allow the stone walls to breath. Existing cement pointing had to be raked out as the stone was becoming damaged. The earth floors in the cottage were replaced with limecrete and a blown clay insulant below to upgrade the U value of the floor to modern standards.

It was impossible to upgrade the insulation value of the windows, doors and walls of the cottage due to its listing, and the resultant loss of the character of the old structure. Unfortunately this does mean that the presence of the cottage does drastically alter the SAP figures distort the measured performance of the new structure.

On site construction

The first phase was to restore and adapt the existing cottage. There were limitations on permissible alterations to the cottage itself, but the fabric of the building was upgraded. The new kitchen and bathroom were conceived as ‘furniture’ rather than built in as far as possible to avoid changing the shape of the original rooms. Water based underfloor heating was installed to avoid the use of visible heating systems.

The second phase was to install sheet piling following the profile of the back edge of the new building, which was anchored with ground ties. Excavations were then commenced for the final phase of construction.  The living area has a 23m long structural glass wall with a cantilevered corner for unobstructed views over the landscape.  The cantilevered edge, needed a massive concrete keel underneath to support a weight equivalent to 200 people partying away at once.  Meticulous checking on site had to be done prior to the many concrete pours to check every last detail, from light and power sockets to door pivots and electric cable runs.  Found supervised the build throughout on site every week to check details and discuss queries.

Conclusion

The interior is minimal but warm – due to the natural elements – the stone and even the stacks of wood for the fire. The restricted material palette inside and out is a unifying factor but within that allows for a play of textures – rough and smooth, natural and manmade, irregular and precise.

The project has been widely published, won a RIBA national award and was shorlisted for the Manser Medal.