Wow factor metal extension to grade II listed barn

OWNERS Laurence & Debbie Osborne

PROJECT Extension

LOCATION Cornwall

SIZE 55m2 (195m2 whole house)

PROJECT COST £145,632

COST PER M2 £2,648

Debbie and Laurence Osborne loved the 18th century barn conversion that they bought back in 2000, but wondered if they could bring in more sunlight. “An old barn with 1m thick walls isn’t the brightest of places,” says Debbie. “That was what drove the idea for a garden room extension. Plus, we wanted a bigger living space to cater for our growing number of grandchildren.”

The property’s grade II listed status and position next to a grade I listed manor house meant the couple weren’t optimistic about their chances of gaining planning permission. But a meeting with English Heritage confirmed that a contemporary addition could work.

Utilising the design skills of their architect son, a plan evolved in the style of a lean-to cart shed with a clear visual distinction from the barn. The external covering was key to setting the new space apart from the stone building, so cedar cladding and a zinc roof was chosen. “The metal covering was a factor that had come up in the course of our conversations with English Heritage,” says Laurence.

As ample natural light was core to the brief, the extension would be positioned to the west of the house and feature large spans of glazed doors. The plans gained planning permission and listed building consent without any issues.

A steel portal frame with timber infill panels was chosen as the structural system. “The metal skeleton was important for us to achieve the big open spans inside,” says contractor Jonathan Rogers from JDS Properties & Developments. The couple chose not to get hands-on with the build, but as no work was being done to the original property, they were able to carry on living there, so were around to see things progress.

The major challenge was uniting the new extension with the 18th century building. “We were working with an old barn with walls that weren’t truly straight – they flared out towards the bottom,” says Jonathan. “Tying a modern addition into a heritage building can be tricky.” Each element had to be carefully measured and cut to the exact size needed – a painstakingly precise process that paid off.

Debbie and Laurence now have a large living-dining space that connects seamlessly with their garden. Slate tiles flow from the extension out into the garden and the bifolds can be drawn back to blur the boundaries between inside and out. “This is our house for life,” says Debbie. “If I was to do it all again, I wouldn’t change a thing.”

Full story online: www.self-build.co.uk/osborne