Discover how this striking steel-clad extension has transformed a farmhouse

red corten cladding on extension
A bold new extension to a farmhouse has provided a healthy new space. (Image credit: David Barbour)

Two build projects carried out by the homeowners on a former farm building in rural Stirlingshire couldn’t be more contrasting. The first, following their original purchase of the property, saw the couple create a new home in the shell of an old barn, retaining as many of the old walls as possible and externally rendering the house to match the original farm buildings.

20 years later, they decided to begin designing and building an extension, which is as unequivocally contemporary in looks, materials and eco-tech as it’s possible to be.

“We enjoyed the many levels of the existing house, but more recently realised that we would require the comfort and convenience of a ground floor bedroom and bathroom at the same (ground) level as our most important living space, if we were to continue living on our piece of heaven,” say the homeowners. 

“In terms of design we wanted something that would be exciting and contemporary, not a square timber box. And we didn’t want something clinical looking, despite accommodating our various health needs.” Here's how they created their striking extension.

Designing a modern addition to a period home

Having spotted several projects that used corten steel in their design, the couple were thrilled to discover that one of the corten-clad houses that they admired was designed by local Stirlingshire-based architecture practice Paper Igloo.

Following discussions with Paper Igloo architectural designer Martin McCrae, his response was to design a new extension that would sit comfortably within the ruined walls of the old barn.

“From a practical perspective this was the best location as the clients needed a level route between the ground floor sitting room and their new bedroom, which was previously on the upper floor of their two-storey house,” Martin explains. 

stone cladding on small extension to farmhouse

A new large panoramic window was installed into the original sandstone walls of a second old barn on site. (Image credit: David Barbour)

Using contemporary exterior materials

The single storey extension was designed to be visually separate from the existing house via a full glazed link; apart from this element, the new structure is entirely clad in corten steel.

“We wanted to pick up on the deep red colour of the render of the existing house,” explains Martin. “In addition there is a young Acer Griseum tree (Paperbark Maple) with peeling chestnut-coloured bark and red autumnal foliage, which sits at the corner of the ruined walls and is visible as you approach the house.

“When viewed together this creates a strong and vibrant colour palette of deep reds, browns and greys. These colours are offset by the greens of the lush garden and surrounding agricultural countryside.”

small extension with glass link and corten cladding

A fully glazed link bridges the original and new structures. (Image credit: David Barbour)

Building a healthy home

The timber frame extension has been clad in corten steel-clad and insulated with natural wood fibre insulation creating a breathable, vapour open wall construction. The windows and doors are all highly efficient alu-clad timber.

“We undertook a series of ‘interstitial condensation risk analysis’ calculations to ensure there was no risk of condensation forming within the construction,” explains Martin McCrae of Paper Igloo. “As a Section 6 Certifier we often undertake this process when we are doing our U-value calculations for the Building Warrant.”

Martin says: “We had to ensure that the new construction did not negatively affect the ‘health’ of the sandstone, so we designed a ventilated cavity between the new timber frame wall and the existing sandstone wall.

“This, coupled with the use of hygroscopic eco insulation materials, allows any water vapour that may otherwise condense within the construction to evaporate fully, thus preventing any potential for damage to the building materials over time.”

accessible bedroom in extension with plywood lined walls

The alu-clad windows are from Rationel.  (Image credit: David Barbour)

Visually, the new extension creates a sculptural effect. Because the project was designed to cater for the couple as they grew older, level thresholds from the old farmhouse through to the new extension were essential.

“This project gave us the opportunity to play with our ideas of contemporary architecture,” say the homeowners. “We now have a great corten-clad extension with not a single right angle in it, set within the old sandstone walls, and which fulfils all our requirements. This is a wonderfully comfortable home where you can relish the views, the garden and the birds outside, as well as the clever design and lovely finishes of the rooms inside.”

Homes Journalist

Caroline Ednie is an experienced homes journalist and editor based in Glasgow. Caroline has written for The Guardian, Scottish Homes & Interiors, Dwell, House Beautiful, Real Homes and other self build titles, to name but a few, and has interviewed hundreds of architects, self builders and home renovators during her career. She is also a former web editor of Architecture and Design Scotland.