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Group 19’s deep retrofit of a Berkshire bungalow

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Words:
Matt Hopkins

Continuing our series on ways to keep homes warm without killing the planet, Matt Hopkins of Group 19 Architecture & Urban Design explains how extending upwards proved the most energy-efficient way of transforming a bungalow into a large family home

Kiln Ride was originally a 1950s bungalow owned by our client's parents, who had to downsize. The client saw an investment opportunity to develop the bungalow – her childhood home – by transforming it into a large family house for sale. 

The building, in Finchampstead, Berkshire, originally comprised five internal rooms with a front porch and rear conservatory. It also came with a garage and a number of sheds. Our client’s ambition was to create a spacious four-bedroom family home in the most economical and sustainable way, while also bringing its energy efficiency up to modern standards.

Initial feasibility studies showed that the level of accommodation could not be incorporated within the existing volume of the bungalow. An option to add a sprawling rear extension in the very generous garden was considered. However, this would have involved creating a relatively inefficient volume, including a large amount of concrete foundations, in addition to significant retrofitting of the main property.   

To minimise the use of additional carbon-intensive materials, while improving overall thermal efficiency, we wanted to keep the design to an efficient volume and use as much of the original building as possible.

  • Front elevation of the existing bungalow.
    Front elevation of the existing bungalow. Credit: Group 19
  • Rear elevation of the existing bungalow.
    Rear elevation of the existing bungalow. Credit: Group 19
  • Rear elevation of the remodelled house, with additional storey.
    Rear elevation of the remodelled house, with additional storey. Credit: Group 19
  • Rear view of bungalow retrofit project showing timber first-floor extension and roof under construction. Paving blocks were cleaned and reused for the driveway.
    Rear view of bungalow retrofit project showing timber first-floor extension and roof under construction. Paving blocks were cleaned and reused for the driveway. Credit: Group 19
  • Landing of the first-floor extension, with framed view of trees.
    Landing of the first-floor extension, with framed view of trees. Credit: Group 19
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How we did it

We worked closely with structural engineer Spark Structures at the concept design stage as we needed to know the potential of the existing structure. We carried out a series of small intrusive investigations and determined that an additional floor could be added, allowing us to keep the works within the bungalow’s original footprint and avoid complete demolition.

We removed the internal walls, windows and roof. All materials were checked, cleaned and stored for reuse wherever possible. This included the roof tiles, bricks and block paving.

Four concrete foundation pads were required in the centre of the plan for a lightweight steel structure to support a timber first-floor extension with vaulted ceilings, and rooflights that bring natural daylight into all rooms.

We completely reworked the ground floor, creating an open-plan kitchen and dining area, living room, utility, bathroom and study. The new first floor includes four double bedrooms, two en-suites, a family bathroom and a small loft space.

  • Open-plan kitchen and dining area with oak bifold doors opening into the living room.
    Open-plan kitchen and dining area with oak bifold doors opening into the living room. Credit: Group 19
  • Landing of the first-floor extension, with framed view of trees.
    Landing of the first-floor extension, with framed view of trees. Credit: Group 19
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Learning from the project

The whole property has been insulated to surpass current standards including the ground-floor walls, where the existing cavity was refilled and insulated plasterboard applied. Underfloor heating was integrated into both the ground and first floors to allow for lower temperature flow rates. Although no performance data has been formally collected, we understand that the enlarged house remained at a consistent temperature throughout its first winter while using less energy than the previous winter.

The reuse of materials including the block paving and roof tiles was generally successful. However, we did require additional roof tiles, which were colour-matched and ordered before the original tiles had been thoroughly cleaned and prepared for application. This resulted in a contrast between the new and the old tiles in a relatively prominent location. 

Original brickwork was filled and painted, but unfortunately, multiple imperfections remained visible. The client elected to render over the original brickwork, taking the project over budget – to £266,000 – but this did significantly improve the property’s appearance.

Reclamation and reuse are not always straightforward. We repurposed used kitchen carcasses from another project, and upgraded the doors and drawer fronts, but encountered some issues with the sizing and functionality that proved difficult to resolve.   

Nevertheless, we believe this deep retrofit project can be a model example of how similar bungalows could be enlarged and brought up to current standards while reusing as much of the existing fabric as possible. 

Matt Hopkins is the founder of Group 19 Architecture & Urban Design

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