Marianne Suhr: Adding an extension onto a period home

Click on gallery image to view larger picture.

Alan and Sarah Tierney had lived in Picketts Cottage for six years when they began to think about extending their 16th century house. They had managed with the smallest kitchen imaginable: a space less than two metres by two metres. ‘By the time the kitchen units were in, there was about 60cm of floor space to move around in, which made cooking a meal extremely tricky,’ Alan told me.

But Alan was also nervous about extending. The house had a largely intact original timber frame that had changed very little over the centuries. The last thing he wanted to do was to create a large opening through the back wall to tack on an extra wing. But the crunch came when he became concerned about the condition of the back wall. The timbers were badly weathered and the decay seemed to be accelerating. Some of the joints in the ancient frame were close to the point of failure – something had to be done.

Dual purpose kitchen
As a specialist in timber frame conservation, Alan knew that he had to protect the back wall in some way to halt the rate of decay. It was at this time that he came up with the idea of a kitchen extension, but his structure would be one that was free-standing, not fixed to the original building, and completely reversible.

‘So many kitchen extensions take no account of the historic building surrounding them; I wanted to build something that could be entirely removed in the future without damaging the original fabric,’ Alan explained. ‘I was also keen to protect the back wall to prevent any further weathering and deterioration of the timber frame.’

I asked Alan if his wife Sarah was delighted at the prospect of a new kitchen, but Alan replied mock-indignantly that he was chief cook and that Sarah would be watching while he cooked. In fact, Sarah even features in the original architect’s drawing, seated at the table, wine glass in hand.

The kitchen design is basically a continuation of the slope of the original roof, but as it would enclose the windows on the back wall, Alan wanted it to be almost entirely glazed to let in the light. He achieved this with a double glazed, glass roof that flooded the extension with light.

Alan was particularly concerned about putting a rigid and impermeable new structure next to a breathable 500-year-old wall that was prone to seasonal movement. So he specified a limecrete (rather than concrete) raft foundation and a limecrete floor. The absence of a plastic floor membrane prevented dampness from being forced to the edge of the extension and pushed up the ancient walls of the house.

Whilst the extension is clearly a modern addition, Alan carefully selected materials that would blend and weather in with the original building and enhance the appearance of the house from the back garden. He chose to build the wall structure out of green oak and used new handmade bricks bedded in lime mortar for the infill panels. Internally Alan selected Pavatherm wood fibre board, rather than plasterboard, and finished this with a lime-based plaster.

So has the new extension been a success? Alan is enjoying all that extra space and, apparently, Sarah’s only complaint is that he designed the kitchen for a giant. At 6ft 4in tall, Alan set the worktops, switches and wall cupboards at a height that Sarah finds hard to reach. All the more reason to leave him to do the cooking.

ABOVE: 1 Erecting the green oak frame 2 The old back wall is protected inside the new structure and the surface finished with a soft lime plaster 3 The first fix electrics are installed and the new lime plaster is applied to the wood fibre boarding 4 Installing the handmade kitchen BELOW: 5 The completed interior with primrose yellow cupboards and a double oven.

Marianne's checklist: Planning your kitchen extension:

• Think about how the extension will impact on the existing building, particularly if it is an old or listed structure.

• If it is listed, have a chat with your conservation officer to understand their concerns before spending money on architects’ plans.

• Take care not to undermine existing footings when digging trenches close to the existing building.

• Where possible, go for a design that is reversible, so that it might be removed at some stage in the future without compromising the historic fabric.

• Try to utilise existing openings rather than creating new ones.

• Maximise natural light, especially if you are enclosing windows; a glazed roof is ideal.

Reno know-how: Alan's three-point guide to constructing glazed roofs

1 The roof structure has to be rigid and movement free. If the structure moves in any way, the joints between the glazing will open up and let in water.

2 Minimising heat loss through a glazed roof is critical. As well as using double glazed panels, they need to be treated with a special coating to reflect heat back into the room. Conversely, reducing solar gain is important otherwise the room would be unbearably hot in the summer.

3 Access for cleaning a glazed roof is very difficult, so it’s worth spending the extra money to get a self-cleaning coating such as Pilkington’s ‘Activ’ range (pilkington.com). Make sure an experienced fitter installs any glazing, and always get a guarantee.

WORDS AND PHOTOGRAPHS MARIANNE SUHR
Featured in the November 2010 issue of Period Living