A wolf in straw cladding

The result is probably the only strawbale and redbrick union in the country and it works wonderfully. "I met an architecture student who had done a thesis on strawbale and he thought it would be perfect for me," says Terry, a charity worker.

The most thrilling discovery was that she could help to build it herself and that is just what she did. Helped by a trusted one man band builder and a posse of friends, she had a hand in everything from digging the foundations and laying the bales to rendering and insulating.

"I really enjoyed the journey. It was so much more satisfying than having a conventional build," says Terry, who moved to Britain from her native America 30 years ago.

The journey started in 2006 when she moved from a larger house in Easingwold to a tiny Victorian cottage with a big garden in a nearby village. The extension was to be a practical application of her belief in "permaculture", a philosophy rooted in sustainability.

"The cottage was very dark, like living in a cave and the stairs were lethal, which is why I decided to remodel everything and add the extension to create a large, light sitting room," she says.

"I got up to plan 876 before I finally settled on what to do."

After opting for strawbale, she met the UK experts at the Todmorden-based Amazon Nails. This team of women can design and build in straw and teach you how to do it yourself. They helped Terry design the curved single storey structure that wraps round the existing building and houses a large sitting room and bathroom.

The extension is at the side of the house, where there was once a small garage. The front of the extension uses the bricks from the garage, while the straw bale structure is masked by a shed so can't be seen from the road.

"That really helped in getting planning permission because no-one can see it, " says Terry. She and her builder attended strawbale and lime rendering courses and work began in April 2008. Keen to recycle everything, she used compacted rubble from the demolished garages for the foundations.

"Concrete wouldn't have been good as it stores damp and the last thing you want is for damp to get into the straw. We went for self-draining foundations, where any moisture can seep away into the ground."

The base was rimmed with a brick plinth and foamed glass board. This was topped with a wooden base plate on which the tightly packed straw bales, bought from a local farmer, could be stacked and staked together.

"My friends helped with the bales and that was wonderful," says Terry. "I had 25 people between the ages of 18 and 82 helping me and most of us were over 50. It only took a week to do."

The bales were secured with hazel stakes and the openings for windows and doors were cut by hand with hacksaws and bread knives. Another strong wood plate was put on top of the bales to help support a conventional roof with an overhang to protect the straw from rain.

It sounds simple, but delays with the bespoke structure were inevitable. As the local authority building inspectors had never dealt with straw before, Terry had to employ a structural engineer to convince them it was safe and strong.

There is no greater fire risk with straw because it is packed so tightly there is not enough oxygen to support combustion. "We really had to show the building was strong enough and prove that the self-draining foundations worked better than concrete would. We also ended up having quite a complicated roof structure as the inspectors thought the original pitch was too shallow, but it was all fine in the end.

"By this point it was September and we hadn't finished the roof. We hadn't even started putting the protective render on the straw, so I was panicking about damp penetrating." She put up tarpaulins and eventually began applying the lime render. "It's lovely to work with but quite soul-destroying after a while because you apply straight on to the straw and push the first coat in with your fingers."

The second coat was done by October, but was supposed to be frost free for three months. She couldn't stop winter, so she wrapped the extension in a bubble wrap jacket which worked a treat and began rendering the inside of the property with clay.

The straw has fantastic insulating qualities but the floors and roof also needed insulating and Terry's next job was to fill the cavities with loose sheep's wool. "The big issue with that is the risk of moths getting into it. So you have to seal every opening with mosquito netting. It was very time consuming."

The project from start to finish took almost two years.

That included significant alterations to the existing cottage, including moving the stairs.

"The work took longer than I thought, but we didn't work on it every day and anyway time wasn't an issue for me."

The cost was also more than she anticipated.

"Because I altered the existing house as well it's hard to say whether a straw extension cost more than a conventional one.

"It's probably about the same but the environmental impact is much less."

The new sitting room feels fantastic and boasts eco-friendly bamboo flooring and stair rails made from oak and hazel. It is full of light, as is the bathroom, which has a clever Sola Vent sun pipe that combines with a solar powered fan and LED lights.

"Everyone comments on how different the extension feels.

"It's so naturally warm and it's quiet because the straw absorbs sound," says Terry. "For me, it is full of memories.

"Yes, it was hard work and stressful at times. But I learned new skills and I learned how buildings are put together and my friends shared that with me.

"It's been a really wonderful experience."

USEFUL CONTACTS

Amazon Nails, Todmorden, strawbale specialists, tel: 0845 458 2173, www.amazonails.org.uk,

Green Building Store, Huddersfield, eco-friendly building supplies and windows, tel: 01484 461705, www.greenbuildingstore.co.uk

Monodraught Sola Vent, for solar powered ventilation and sun pipes, tel: 01494 897700, www.sola-vent.com