Underpinning to support the foundation-free walls of an old barn – the sort purchased by David and Carol Cross back in 2006 – is not a task for the impatient. Owing to the potential structural strain it places on the building, the external walls can only be jacked up one section at a time. Each section can be no longer than 1.8m. As you go along, each section is supported by acroprops and filled in with concrete. It’s not fun, and it is (occasionally very) expensive and time consuming.

Imagine, then, the reaction of David and Carol to the news that not only did their newly purchased barn need underpinning (cue the sound of the contingency coffers emptying) but that this need to underpin had only been discovered after they had completed the first stage of their, as David calls it, “top-down” conversion of the barn into a (thankfully now splendid) family home. David’s face must have been a picture. “The Cornish granite that formed the barn had decayed over time,” he explains, “and there was little choice for us. If the building had collapsed, it’s highly unlikely that we would have got permission to replace it.” Despite being one of the strongest of all the stones, granite in rare instances decays over time — perhaps due, scientists believe, to being in close contact with cement mortars. Also, granite varies greatly in porosity. “We had just completed the new roof structure,” continues David, “so it was a real setback.”

David and Carol purchased the old barn, which came complete with an adjacent cottage (now home to David’s mother), with a view to retaining as much of its charm as possible in the process of turning it into a family home. It enjoys spectacular views over the Helford River valley. Its unusual shape – two angled wings joined by a large double-height circular void – suggests that it may have been used at one time as a grist mill. The grist was corn that would be ground down to be turned into flour and, in the case of David and Carol’s barn, the circular space would have been where the animals walked round in circles, powering the mill.

“Opportunities come up so rarely in this village that it was too good to miss out on,” says David. “The barn had planning consent to be turned into three flats — two downstairs for holiday lets and one upstairs for a local person. It was in really poor repair [as the pictures on these pages testify]. It was seriously overgrown and the roof was in an appalling state — half collapsed, half covered with tarpaulin. Hence our plan to start from the top down. We reapplied for permission to turn it into one house on the basis of unviability of the holiday lets, and asked CSA Architects in Truro to come up with a suitable scheme. Luckily, it worked.”

Permission having been granted, David and Carol then spent the next year landscaping the impressive grounds while a bat and owl survey was carried out, in the meantime preparing for the project ahead — and honing their scheme with the architect. It was quite literally a voyage of discovery. “As we began to clear up the building a little before work could really begin, we actually discovered three new window openings,” says David. “It meant that the scheme now only has one new opening, and is therefore much truer to the original.”

CSA organised the tender process and builder David Trethowan won the contract, despite not being the cheapest. “He was local and really experienced, which was the deciding factor,” explains David. “Builders are used to the intricacies of agricultural buildings round here, and we wanted someone who could realise the design down to the last detail. The aim was to maintain the charm of the existing structure but provide top-quality living accommodation at the same time.” “The floorplan was tricky,” says architect Nigel Atkins from CSA, “in that the road/back elevation of the building is built into the slope. As a result, the view from the top window along the rear corridor gives you the impression you’re at ground floor level when you’re not. As we couldn’t have any new openings on this side anyway, we used that part of the upstairs as a corridor, with the bedrooms enjoying the open southerly aspect.”

Work finally commenced as the window openings were formed and cleared, and the barn was stripped back to the bone, with a completely new roof structure, sitting on new wall plates, erected. This gives the new interior a distinctly chunky feel, enabling the new part of the building to be easily identifiable. The structure itself has been left exposed, with plasterboard infills. While local Delabole slate has been used for the landscaping, it was cheaper to import slate from Spain for the roof, much to David’s amazement. Luckily, despite the requirement for underpinning, the new roof structure didn’t need to come down and be redone.

The outside walls of the barn have been repointed with a lime mortar and cleaned up; new windows and doors, made up in iroko by an expert local joiner, installed and a new rooflight put in to throw light on the double-height circular space below, used now as an entrance lobby. Internally, the walls have been insulated with Celotex which has then been pinned into place through a mesh, which has been rendered in lime to give a pleasingly rough, rustic finish. Builder David has given all of the corners a soft, curved edge, to heighten the feeling of solidity and character. Given the extensive nature of the conversion, it was relatively straightforward to install underfloor heating throughout the house. Local granite has been used to form new garden walls, and, this being an exposed part of south Cornwall, the south-west elevation has unusual slate soffits to protect the structure from the wind. A new garage has been constructed to match the existing barn and enjoys the benefit of a self-contained office.

This is a conversion that is full of charm and really makes the most of its location. The ground floor spaces in particular mix old charm with modern convenience, and Carol, who took charge of the interior schemes, has given the spaces a modern country feel. “Despite the odd setback, the conversion has been a real success,” says David. “We’re delighted with the results, and the quality of the finish matches the design. I feel we’ve improved an old building that was on the verge of falling apart, and saved it for another generation. It has been lots of fun and we’ve learned a lot — not least that I don’t think I’d start from the top and work down again!”

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