23 Jun 2022

Surrey’s Architect-designed Sustainable Stables

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Woodthorpe Stables is an energy-efficient conversion of a Victorian property in Godalming, Surrey, built using natural materials and led by sustainable principles. The design and self-build was realised by homeowner and Architect, Ed Martin of Delve Architects for his young family.

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“My wife, Becky, and I had lived in south London for eight years and were looking to gain more family living space,” explains Ed. “We had renovated properties before, and with house prices in the area above our budget, we started to look outside London. We began initially looking around Teddington, Kingston and Richmond. Once we considered commutes and the main train lines into Waterloo or Victoria station, we soon realised that we had more leeway to move further afield and consider plots of land and neglected buildings. We had more freedom to deliver a genuinely sustainable renovation.

“Due to the small renovation works that we had undertaken before on previous properties, we weren’t daunted by the task. With the knowledge acquired through my architecture practice and Becky’s experience with self-building, we knew that we could do something extraordinary if we found the right place.”

The existing structure

Ed continues: “Becky initially did a lot of research into buying a plot of land, and we spent our weekends driving out to different areas to get a better idea of what might be possible. We used online plot finder websites and set up alerts on websites to see if we could find something suitable. There were a lot of old equestrian sites without planning permission, which we felt could have been perfect. Still, we needed to be within walking distance of a main train station, rather than a car drive away. Eventually, we came across Godalming and the property at Woodthorpe Stables. It had been empty for three years.”

The property itself had been converted to residential use in the 1950s, yet was left vacant since 2015 and was in a dire condition with single glazing, no insulation on the floor, walls or roof, and sparse electrics and lighting. Yet, with the historic stone walls in a sturdy condition, a recently-retiled roof, and environmental considerations, the decision was made to retrofit the stables into a modern eco-home.

Describing more about the style and age of the original building, Ed illustrates: “The original stone haybarn was built in the 1800s, connecting to a larger manor house, which still exists higher up the hill. The haybarn was situated on the edge of the site, sitting alongside the main driveway up to the manor. The previous owner converted the house into a two-bedroom dwelling in 1950.”

Planning permission and the design brief

Recalling the planning process, Ed continues: “We initially proposed a pre-planning application with the council to test their reaction against a slightly bigger scheme. We received their consultation feedback within six weeks and submitted our final proposal through a householder planning application. Before issuing to the council, we dropped plans around to the different neighbours to explain what we hoped to achieve. Thankfully, they all appreciated the central idea of maintaining the historical building and adding to it. So, after eight weeks, we were granted our planning permission with no objections.”

Moving on to how the two finalised their design brief, Ed explains: “We knew as a base level how many bedrooms and what type of living spaces we wanted to construct, but from then onwards, we were free to explore and create. Initially, we looked at assembling a new first-floor level, but it would have taken us over budget, so we kept to a single storey throughout.

“We wanted to show the value of retrofitting old buildings and testing our skills to see how sustainable we could be. The original property was rated with the worst energy rating of ‘G’ when we purchased it. We’re now B rated, which is amazing, seeing as the house has uninsulated solid stone walls. As inspiration, we looked at the extension at the Garden Museum in Lambeth by Dow Jones Architects and the timber-framed construction projects of Feilden Fowles.”

The building process

Ed and Becky started building in October 2020 and completed the build in April 2021. “The project ran roughly three or four weeks over from the original date,” explains Ed, “but this was due to scope changes and the impact of the pandemic on deliveries and the workforce. We also built during a particularly cold winter, which meant some problematic days on site for the construction team.”

Speaking more of the difficulties associated with the build, Ed reflects: “The most complex challenge was accessing the plot, as the building sits right on the site’s boundary against a pedestrian walkway and roadside. Deliveries needed to be carefully coordinated and timed not to block the street. We also started building in 2020, delivering the project through the different lockdowns during the pandemic.

“Working with an old building meant we weren’t quite sure what we would find until we started to take it apart. Under the concrete slab, we found the original cobbled floor of the stables. Space was at a premium during the build, but we tried as best we could to store demolition material for re-use. The cobbles have been used as paving externally, while all the internal brick partitions were carefully taken down and stored for re-use around the building.”

When asked if they remained within their forecasted budget, Ed said: “We completed a lot of excavation work around the building to dig it out from the hillside – the stone haybarn had been built, then surrounded by earth on two sides. The excavation and size of the retaining walls were increased in strength and depth to ensure we didn’t have any future problems; this added £5000 to our build. Our decision to switch to a completely electric system instead of gas added a further £8000 onto our build. We had hoped to utilise the Government’s Green Homes Grant scheme for our project, but this was pulled after three months of waiting to see if our application had been approved. Instead, we took advantage of the existing Renewable Heat Incentive scheme, which effectively pays us back our investment in arrears rather than upfront, up to £7000. Some existing timber rafters were rotten and unsalvageable, which added additional extras to our budget.”

“We moved back into the property in April 2021, as soon as the works finished. We decided to leave packages of work to a later date to help financially with the cost variations that occurred during the build.”

The finished home

Completed in 2021 after a six-month construction period, the work stripped the stables back to their original character. The building now uses Douglas fir timber framing, adding 25m2 of space for the two-bedroom home with open-plan living areas, a courtyard, playroom, larder and utility room.

“The original building is built of Bargate stone – a sandstone material found locally in the area,” says Ed. “The existing stone and red brick walls have so much character that we decided we had to keep it all exposed. We wanted our project to be as sustainable as possible, so we knew we were looking at timber-frame construction for any new element. The lightness of the timber contrasts against the stone to create a clear division between new and old.”

Ed and Becky followed a sustainability-first strategy when it came to material specification. As Ed explains: “Our approach was to try to use materials that were chemical free and as close to recyclable as possible. The insulation in the floors is recycled glass, and the walls and ceilings use wood-fibre boards instead of plasterboard and are finished off with a breathable clay plaster finish. The extensions are built using timber-framed construction in Douglas fir and match the new windows and glass doors. Any new works to the stone walls used lime mortar to correspond with the original construction techniques. Our new flat-roof areas are finished off with green sedum living roofs to absorb rainfall and reduce our surface water runoff into the nearby sewers.”

This use of sedum green roofs not only increases the house’s capacity to stop surface water runoff into the mains sewer system but also improves thermal performance and finally gives the neighbours wildflower views which they continue to comment on.

Other than Douglas fir, selected for its lower price point over oak and its durability, Ed took the opportunity to integrate materials and systems to create a healthy building that has flexibility for the young family to grow.

Energy saving

An air source heat pump was installed, with a complete wet underfloor heating system laid within the concrete slab foundation throughout the house, which will work in tandem with solar panels and battery storage to lower the heating bills by 80% in the long term.

Ed explains: “We needed to upgrade our gas boiler and water cylinder, so we chose to cap off the gas supply, switch to an air source heat pump, and run the house entirely on electric. The project’s design allowed for additional sustainable elements, such as the roof, which we’ve prepared to install solar panels and an electric car charging point later.”

For the floor insulation, Ed chose a new system of recycled glass pellets from glasscrete, which is held together with a series of breathability fabric liners. The glasscrete’s impressive compressive strength can sit underneath the slab and wraps around the footings to give a completely lined base to the building. The thermal performance ensures that the underfloor heating worked to its maximum potential, even in the exposed vaulted spaces of the barn.

Externally, cladding was done with cedar shingles to match the hanging clay tiles from neighbouring properties. This allows the cedar to naturally silver over time to bed the extension into its surroundings against the pale Bargate stone.

Building materials

When asked if there were any materials he would recommend to others looking to renovate or self build, Ed responded: “Companies like Mike Wye and Natural Building Technologies have a great selection of products to consider against the more standard construction materials. Wood-fibre insulation add both thermal and acoustic properties to walls and ceilings, making them an excellent alternative to the chemical-laden plasterboards often used in construction. Clay or lime plasters can be pigmented to give the final colour, reducing labour times between the standard approach of plastering and then decorating. The clay allows the walls or ceilings to breathe and filter the air within the rooms.”

The consensus

Describing the building’s connection with its surrounding area and revealing what the local community thinks, Ed adds: “With the excavation to the west, we now have direct access into the garden from the main living spaces. We have small amounts of glazing to the south, but we opened up the northern facade to fill the house with light. The glass walkway can slide open in the warm summer months, allowing the whole place to flow between the different courtyards.

“We’ve received lots of positive comments from our neighbours and passers-by, who frequently ask if they can pop their heads in to see what we’ve created. The green sedum roofs aren’t visible to us, but they give the local neighbours bright, natural colours to look at instead of flat, grey asphalt roofscapes.”

Final thoughts

Ed admits: “I don’t think we could quite imagine how spacious the house would feel once all the vaulted ceilings were exposed and the original mezzanine above the kitchen taken down. The original house was cold and dark, with barely any lighting. We now have light-filled rooms and flexible spaces to enjoy as a family.

“The glass corridor addition allowed all the bedrooms to use the full depth of the original building. This has really helped ensure we have decent-sized bedrooms, while the ability to open the walkway to the courtyard during the summer months is a special treat for us.

“To the west elevation, we built a new dining pod that sits off the main kitchen. A large set of windows sits almost at ground level, meaning we can relax and enjoy the view of our wild flower bank and the nature around us.”

When asked if there was anything the pair would have done differently, Ed confessed: “When we bought the property, the existing roof had been replaced in the last 10 years and was in excellent condition. This meant we decided to spend our budget elsewhere in the project and insulate from underneath/inside the property. Adding insulation between and underneath the rafters has meant we’ve lost sight of the original purlins exposed as part of the original hay barn structure. It would have added an extra £10,000 to £15,000 onto our build, but maybe on reflection, we could have removed the roof and started afresh, giving us more view of the original character internally.

“Would I do it again?” reiterated Ed. “Yes, definitely. It was a great learning experience and an opportunity to try new things and test sustainable materials. If we ever take on another project as a family, it would be a self-build from scratch.”

Offering his professional guidance to anyone looking to renovate or self build, Ed reveals: “The beauty of architecture is that there is never a right or wrong answer. Our advice at Delve Architects would always be to explore the options and possibilities at the beginning of a project. This lets you consider what is right and best for you before moving into the more costly stages of detailed design and onsite works.

“Work with an architect who you feel you can talk things over with and who will give you the best advice possible on the different routes to take. Make sure you provide the contractors with a complete set of architectural drawings and written costing documents to avoid confusion on site and ensure that everyone is on the same page in terms of what is and isn’t included with the specification.

“Finally, have a clear sense of timings, finance and your desired scope upfront. Initiate conversations with potential contractors as early as possible and look for a good match to work with people who appreciate what you are trying to achieve.”

The designs completed at Woodthorpe Stables allow for future phases of construction work to create a new entranceway into the property and a final pitched extension that will ultimately house an additional bedroom and bathroom for Ed and his family.

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