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Eco house on a budget

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Explore an affordable, sustainable home built for just £81,800
Woodland eco house on a budget
The raised house is approached via steps
The interiors are inspired by oriental style
The floor has been sanded and painted to look like poured concrete
The bedroom benefits from plenty of natural light
The north room is a light-filled space
The single-storey house is topped with a green roof
The cantilevered north room stretches out into the woodland

On Joshua Penk’s 20th birthday in 2009, he poured the steps for his new home. “Building had always been on the cards for me. The plot has been in the family for quite some time,” he says.

In fact, Joshua is in the third generation of his family to self build. The large, stunning plot where his home now stands is set deep in Cornish woodlands near the south coast and was bought from his grandmother in 1989.

Striving for sustainability

Joshua first became inspired by sustainable building when he did work experience on an award-winning local school with his father’s design practice, ARCO2. He later delayed going to university so he could work; first in the practice’s offices, and later on his self build.

Fact file: Joshua Penk

Location: Bodmin, Cornwall

Project: Self build

Style: Contemporary

Construction method: Lightweight post and beam

House size: 220m2

Land cost: Already owned

Build cost: £81,800

Cost per m2: £372

Construction time: 40 months

Current value: £500,000

“It was important to learn the system of building. The practice does all the elements of a job, from planning to production,” says Joshua, who drew up his own home’s design at the same time. The result is a striking, single storey, two bedroom property built in a curve, using a post and beam system with cedar cladding and a spectacular glazed south elevation.

“I knew that a single storey would be easier to keep low impact, and it was also much simpler to stick to a small budget,” says Joshua. “But primarily, it was a stylistic decision inspired by the design of Japanese homes.”

The hands-on self builder did almost all the work himself on a shoestring budget of under £82,000, so was keen to avoid using heavy machinery and permanent scaffolding. “We managed to do the building with no scaffolding at any stage of the project, using a block and tackle,” he says.

The lightweight structure sits on pad foundations, with a cantilevered room over a stream to the north. The design embraces many of the latest sustainable building techniques. “It’s very eco-friendly,” says Joshua. “There are no synthetic materials, so it’s extremely breathable.”

From planning to reality

Joshua’s family gained permission on the plot in the 1980’s and had laid services at the time, which helped with the budget. Nevertheless, the original permission had lapsed, and he had to re-apply for full consent – which was granted.

In keeping with the ethos of the whole project, he undertook his own tree, soil contamination and mining surveys (with a little help from a geologist neighbour). In fact, Joshua avoided using consultants and sub-contractors throughout – with the exception of a plumber and an electrician to do the final fix, commission and sign off.

As a result, he quickly learned various new building skills. “I learned to start in an inconspicuous area first and gradually improved, as there is so much repetition,” he says. “On each birthday, I recruited the entire family to do different jobs. There were three generations of us; it was a lovely experience.”

Material matters

The key to the success of this build has been Joshua’s choice of materials, which are natural and locally sourced. For example, the wool insulation is a by-product of the fleece industry in the south west, and was collected for Joshua by an agricultural merchant. The straw insulating material is from his uncle’s farm.

The Douglas fir posts came from Duchy Timber in Cornwall and the cladding from a tree on the plot, which was felled during the preliminaries. “We think it is white cedar or macrocarpa. We milled it on site into large planks in 2008 and left it to season,” says Joshua.

The house is raised off the ground, with big roof overhangs so the straw and wool insulation doesn’t get wet. The radial frame is built from gulam beams (sourced from Finland, as there were no production manufacturers in the UK at the time) and is knitted together with home-engineered joists in the floor, roof and walls.

The lightweight building rests on 50 pad foundations, each filled with low grade concrete. The posts sit on top of these, inside concave saddle stones. “We were proud of those, as they cost about £2 each, while the proprietary feet were more than 10 times that cost,” says Joshua.

Rather than buy a ready-made green roof system, Joshua designed his own ‘breathing roof’, using water-resistant bitumen board, a rubber-based liner, battens and a structural ‘bubble wrap’. The top is spot planted with little sedum and ferns, which were free seconds rescued from a commercial project as they came off a damaged roll.

Eco interiors

When it came to heating, Joshua chose to combine the traditional with the cutting edge. “I knew I wanted to go log-fuelled, as the woodland can amply support my needs.” he says.

He searched the internet and found Welsh company Grey Metal, who supplied him with a woodburning stove, backburner and oven for just £650. “The setup heats two cylinders of hot water, one of which supplies the underfloor heating,” says Joshua. “In the summertime much of the domestic hot water is provided by rooftop solar thermal panels from Navitron.”

The solar room on the south elevation, which runs the length of the house, is designed to buffer heat loss and gain, keeping the living space at an optimal temperature. Joshua is very proud of this element of the design.

The interior finish is as original as the construction, and Joshua describes it as “neutral, modern design.” Most immediately noticeable are the walls, which are finished either with birch plywood or with a product called Panelmox, which is pressure treated gypsum and wood fibre that doesn’t need finishing.

He sanded and painted the floor with a water-based acrylic varnish to look like poured concrete. “As a self builder, this was much simpler to do. It looks like concrete and also transfers heat well and is easy to repair,” he says.

While he remains an architecture student, Joshua’s house is let to his aunt, but he returns in the holidays to enjoy the result of all his hard work, energy and vision. “It’s nice when I get to come home and spend time here,” he says.

Words & Photos: Alex Pratt

Published: Build It November 2012

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6 comments

trensporter
Posted on
18/09/15

really do like this eco house on a budget of 81 000 pound looking to do so in hastings in southeast of brighton , looking for to fine the cost of having that house build from sombody , how mush that eco house will cost to be build , thanks

Limousin house
Posted on
24/07/16

Can anyone recommend a good company who supply eco kit houses in France. I will be moving to Limousin and am thinking about building an energy efficient house. Thank you.

silvee
Posted on
23/10/16

nicely done and a clever chap, the setting of course really helps, it looks very tropical, my plan is to have a small eco house built once I have found a suitable plot, maybe I will look up Joshua for his architecture services.

Philsy
Posted on
09/02/17

Nice style open and uplifting.

ifd66
Posted on
10/02/17

We built an eco house 3 years ago very cheaply. Technically it was a half self-build. We did a lot of the work but with q builder doing the more skilled and technical work.
The key is to find a builder who shares your vision and is prepared to use refurbished, reclaimed, up cycled materials. something a company will not probably be prepared to do.
Also they should be flexible and happy to use materials they haven't used before. We built ours in Japan where eco friendly building features are used very rarely - very poor awareness about insulation etc.

moshjosh
Posted on
27/10/17

Wow, Joshua, how uncanny my name is Joshua also and this has been a dream of mine since I was a lad. I just got married last week and my wife and I have expressed a real desire to make this happen as one of our family goals. Could I ask some advice from you mate?

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