A three-bedroom eco-house for £30,000

three-bedroom eco-houseThis house in Basildon in Essex demonstrates how self-build can create fantastic value for money – a low-energy, three-bedroom, two-bathroom family house built by its owner in 1996. The house shows another way of building in timber: this time with load-bearing panels for simplicity and economy, but on timber floor beams spanning between concrete pad foundations which significantly reduces the extent and cost of the foundations.

A plotlands plot

John Little and his now wife Fiona Crummay had restored a 1930s semi, but were now looking for fresh challenges. They had an interest in wildlife, and saw the potential of a near derelict four-acre plot in Laindon near Basildon, not far from where they had been living. The plot came complete with a tiny little two-room house built in the 1920s. The site is in an area of small plots which were made available at low cost during a period of agricultural depression. Many working-class families from the East End of London were able to buy plots and develop them at the outset with a small weekend cabin. Many people subsequently moved out of the city and established new communities scattered around Kent and Essex, the east and south coasts and in the Thames Valley, as Colin Ward and Dennis

Hardy described in the preface to their book Arcadia for All. The site is around the corner from the Plotlands Museum, where an original plotlands house has been preserved.

A modern plotlands house

John and Fiona’s plotlands house was very charming with its little veranda, but the bedroom was not much larger than the bed and they were keen to start a family. The house had almost no insulation and was freezing cold in winter. It had an asbestos cement roof that was beginning to crumble, and its timber frame was beginning to rot. It would have to be replaced, but John and Fiona were keen to build in sympathy with the plotlands idea. The new house would be built of timber to be economical, human in scale, simple and unassuming, but provide modern standards of comfort. With the passing of Town and Country Planning legislation starting in 1948, the area became designated as green-belt land, to be protected from development. However, the planning authority was happy to support the idea of a modest, single-storey, weatherboarded building designed to be sympathetic to the plotlands model to replace the existing house. They agreed to relocate the new building to a position higher up the slope of the site, which meant that the house enjoyed a panoramic view to the south, with the Thames and north Kent hills in the distance. The house was furthermore sheltered from the north-east by trees and a high, dense hedge.

The layout of the house

The simple, single storey plan is laid out with rooms arranged along the contours, all facing south, starting with the principal bedroom and en-suite bathroom at the east end. This room has its own small private balcony. Then comes the large living-room, with space for a dining-table, and a wood-burning stove with the kitchen and walk-in larder in an alcove at the back of the room. There is an extensive deck that is partly roofed with white panels, which protect people and building from the weather, provide shade both inside and out, and serve to reflect light through high-level windows up onto the ceiling and back into the living-room. There are two small children’s bedrooms and a shower room at the west end. The building is tucked into the hill under a grass roof made from turf cut from surrounding meadow. The roof slopes down over the garage on the north side, reducing exposure and bringing the grass roof down almost to meet the meadow behind the building. John has since built a number of outbuildings and sheds, all with grass roofs, which look wonderful and make the buildings fit together visually and look as if they have always been set within the landscape.

Green roofs

Green roofs (rather than grass roofs, for they can support a variety of plant life, not just grass) are not just good to look at, for they have a number of practical benefits – they create new habitats on the roof to replace those lost by building on the ground, and these habitats support a wide range of wildlife, including rare insects, as shown by a British Nature study of green roofs in urban areas. A green roof also holds a large amount of water after it rains, and thereby reduces storm-water runoff. This reduces the load on the storm-water system and reduces the risk of flooding. This is a particular issue in urban areas, and London in particular, which has a combined drainage system. The sewage treatment works have a limited capacity, and so periodically when there is heavy rainfall, large quantities of untreated sewage are dumped in the Thames. The soil of a green roof acts as a thermal buffer and will tend to keep the building warmer in winter and cooler in summer.

Contrary to popular mythology, it is not necessary to mow or maintain a grass roof; it can be left to grow in its natural state and attain a balance of different plants which will grow in the conditions. The shallow depth of soil will limit growth, and the vegetation will go brown and die back during dry spells in summer. It is possible to incorporate measures to retain moisture in the roof, but this can be very expensive and is never very effective. It is also possible to create more of a garden effect by having a substantial depth of soil and planting significant plants and shrubs, but it is expensive supporting the weight of soil.

It is possible to use a lightweight system consisting of a plastic mesh containing a seeded lightweight growing medium. This reduces the cost of the supporting roof structure, but is itself expensive. John and Fiona’s grass roof on the other hand is simply turf from the paddock at the back of the house laid on around 75mm of soil on a layer of geotextile membrane which protects the single-ply roof membrane. The roof is pitched at about 15°, and drains to a shingle margin laid behind an upstand at the edge of the roof which retains the soil on the roof. A green roof can be at any pitch between about 30° and dead flat, but at a pitch of 30° or so, netting or battens will have to be incorporated into the construction to prevent the soil from sliding. It is important that the soil is of poor fertility to encourage wild flowers which can survive the hot, dry summer conditions and to discourage those species which cannot.

The structural arrangement

The building is conceived as a conventional timber- frame structure with wall panels, but instead of being supported on a continuous foundation below the walls, it is supported on concrete pillars. Timber beams span between these concrete posts at ground- floor level. This arrangement combines the advantages of the simplicity and economy of timber-frame panel construction with the benefits of the simple and economic foundations of a Walter Segal method post and beam frame. A conventional stud panel construction made of timber studs nailed together at 600mm centres is easy and cheap to build, but generally requires to be fully supported on a continuous foundation. A Segal house, on the other hand, is supported on calculated timber columns bolted together between 3 and 4 metres apart, each standing on a separate isolated concrete pad foundation 600mm square and 900mm deep. The structural frame has to be made of high quality timber, and is generally more expensive than a stud frame, but the extent and cost of the foundations is substantially less. The combination of panel construction supported on isolated pad foundations makes the most of both systems by combining an economical structure on a reduced foundation arrangement.

Cost-effective foundations

I estimate that relying on isolated bases below each post can reduce the extent of the foundations to around 10% of the foundation needed to support a conventional brick wall. It also removes the necessity of levelling the site, and so John and Fiona’s house appears to float above the landscape. Steel reinforcing rods had been cast into the concrete bases and left sticking up. Drainpipes were used as permanent shuttering and placed over the reinforcing rods which were then filled with concrete to form the supporting columns.

Energy-saving measures

The roof has 250mm of insulation, the floor 200mm and the walls 150mm. This gives U-values of 0.13, 0.18 and 0.20 W/m2 °C respectively. The windows are of high-quality double-glazed timber, made in Denmark. The house has a large amount of southfacing windows and benefits from passive solar gains. It has a central heating system installed, but this is seldom used as the wood-burning stove fuelled by wood waste from a friend’s arboricultural business based on the site generally provides enough warmth.

Value for money

The house has an area of 100m2 and the basic house cost £28,000 to build in 1995. This cost was increased by spending a bit more on some of the equipment such as stainless-steel electrical accessories, elegant radiators and a gas-fired Aga in the kitchen which runs the heating and hot water. This increased the cost to £38,000, but even so this represents stunningly good value for money. Costs were kept low as almost all the work was carried out on a self-build basis. John was taking time off working in the family-run shoe shop, and his brother – a local small builder – and his father who had part- built his own house provided the rest of the effort.

The Grass Roof Company

The house is now surrounded by a lush native wild garden planted with thousands of trees and shrubs and a wildlife pond. There are a number of timber, grass-roofed outbuildings designed and built by John, who gave up the shoe business years ago and has now established the Grass Roof Company with his brother designing and building extensions and small buildings for schools and the like.

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