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How an earthen floor can be incorporated into a modern,

contemporary new build.

Furzedon is a new build which was built in a small village in rural Devon. The build is an unusual amalgamation of traditional local methods, compacted earth flooring, and modern sustainable, low impact building methods and materials, combined to produce a beautiful modern living space.

IntroductionTruro

ExeterOkehampton

Furzedon

Key dates Construction : 2003 – 2005

Exterior - Photo © Jan and Jerry Sharpe - J&J Sharpe

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ContextJerry Sharpe has had years of experience working on conservation projects using traditional building methods, and his company specializes in the supply and use of cob and lime in construction. Jerry and his wife Jan wanted to create a family home whilst making the building as sustainable as possible within the design used. Through their business, they had grown to love cob as a building material and wanted to see how they could combine their love of the traditional, with their desire to achieve a modern living space. Their love of natural traditional building products developed even further whilst on holiday in Arizona. Janet was inspired by an earthen floor they had watched being laid, and thought that this would make an unusual addition to their new home.

Jan and Jerry used the specialist architects Bedford and Johnson, because of the specialist nature of the materials being used. The modern contemporary design meant that the materials would be used in a very different way to the normal traditional cob built cottage. They discussed their vision, gave the architect the sizes of the rooms that they were hoping for and the architect came up with a design from there. The building is built within a conservation area ; therefore, there was stringent scrutiny of their planning application. It took three attempts to obtain planning permission for the build, so each time the plans would come back to the table and options would be discussed.

Plan © Jan and Jerry Sharpe - J&J Sharpe

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Building overviewFor this build, the idea was to use the earth from the site for the cob and earth element of the house. Because of the geology of the area and the risk of radon, a radon barrier was needed at the base of the build. Because of the height and design of the house, reinforced concrete was needed for the basement area below ground level to comply with building regulations. Specialist engineers were brought on site to help build this part of the structure. The central part of the house is a large open plan hallway reaching the full height of the house, with a glass balconied, soft wood walk way joining the two halves of the first floor. The hallway contains full

height glass windows, which were placed as part of the passive design. The glass used is 1.7 U-value; this could have been higher, but the choice was restricted due to the high cost. The basement floor is engineered laminate made out of hard wood. The use of laminates and composites in some cases throughout the build was again a decision made based on the cost of materials. The cost of solid oak is high, so this had to be taken into consideration when thinking about where this would be used. The floor of the ground floor kitchen is made from compacted earth which was then sealed. The other floors on the ground floor are solid oak boards on top of sand and cement screed. The upper floors are locally sourced softwood floor

Cob mixing - Photo © Jan and Jerry Sharpe - J&J Sharpe

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Technical focus: A compacted Earthen floor Furzedon is significant as the use of a compacted earth floor in a new build is very unusual in the UK. Jan and Jerry wanted to incorporate an earthen floor into their home as it would complement their sustainable build concept and the use of earth in

boards.Heavily insulated block work was used to comply with building regulations and built up to sill height on the ground floor, the EPS (Expanded Polystyrene) within block work is 300 mm. Cob work was then used from sill height to top of building, and as mentioned earlier, the materials for this were obtained from the site. The beams used in the main framework for the house are composite I-Beams. The roof insulation is a product called Warmcell™, it is recycled newspaper which is pumped into the roof space. The interior and exterior walls are lime plaster which Jerry Sharpe produces himself as well as being a supplier through his internet site. A Passive whole house ventilation system was used, with a fan based in the roof-space and the pipe

First cob lift - Photo © Jan and Jerry Sharpe - J&J Sharpe

work for all extractors linked to this. No heat recovery or dual flow ventilation was used due to the cost of a heat exchanger.Solar panels are used for hot water and the heating is provided a combination of under floor heating and a wood burner.

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the cob walls. Compacted earthen floors, are the oldest method of providing an internal floor, and are still quite common in dry parts of the world. As this was a new process for the team using the type of soil found on the site, Jerry decided to run a program of test runs. The team constructed a series of small panels, 400 mm x 600 mm, where different mixes of soil, chopped straw, coarse sand and lime were mixed together and dried in order to determine a suitable mix. A larger test panel was then constructed, 2 m x 1 m, to test the strength and extent of cracking on drying. Having determined the most suitable mix, work started on

constructing the 40 sq m floor. The floor was to be put down to a depth of 60mm and required 4 tonnes of sieved soil. This would have been a large labour requirement if done by hand, so the sub- soil was taken off site to be mechanically sieved (screened). Nothing bigger than 10 mm was allowed through the sieve. The sieved soil was then mixed dry with the other materials in a concrete mixer, and then emptied to be mixed with the water using a rotivating mixer. This method was used because when the water was added to the mix in the cement mixer, it stuck to the sides and could not easily be taken out of the mixer. In order to manage the laying of the floor, the 40 sq m area was divided into 4 sections and the mix poured

Earthen floor - Photo © Jan and Jerry Sharpe - J&J Sharpe

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out, using wooden frames to hold the mix and provide a datum line. The mix was tamped down using straight lengths of wood, using spirit levels to ensure accuracy. As the mix dried, the floor was smoothed out, or floated. On a small area this can be done with a hand float, however due to the size of the floor, a mechanical planer was used. As mentioned earlier, earthen floors are still relatively common in drier parts of the world, however, Devon does not have a climate conducive to forming a compacted earthen floor. Devon has high rainfall and is often damp, which increases the drying time. This was overcome at Furzedon with the use of two industrial dehumidifiers, which needed to be carefully controlled.

If the floor dries out too quickly cracking can occur so in order to try and avoid this, a hand water sprayer was used and any small cracks were hand floated out. However, even with a well-controlled drying process, some cracking due to shrinkage can be expected.A floor of this size takes approximately six weeks to dry out if the weather conditions are good, dry and windy. It took four people seven days to mix and lay the floor, which highlights the time and work required in comparison to a concrete floor and then, even with the use of the dehumidifiers, it took about a month to dry.After the earthen floor had dried

Earthen floor completed - Photo © Jan and Jerry Sharpe - J&J Sharpe

StakeholdersMain contractor : J&J Sharpe ltdArchitects : Bedford and Jobson Slating : A Mason RoofingGlazing : Oakhampton GlassSolar heating : Southern SolarJoinery : WD Joinery

out, it had to be sealed in order to avoid dust coming off of the floor. Linseed and turpentine was used to create the seal. The first layer was just linseed. Then the mix started from 75% oil 25% turpentine, gradually reducing the proportions as the layers were added, until it was 10% oil 90% turpentine. It took 10 layers until they were happy that the process had been successful. This method ensures the oil penetrates into the floor until it is saturated and the floor then hardens to a hard resin. Finally, a shop bought liquid wax polish was added to the floor for protection as it was a kitchen floor. The floor has been successful and has provided a hard, durable and waterproof surface. A wax polish is added once a year and any small cracks are filled.

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Photo © Jan and Jerry Sharpe - J&J Sharpe

Photo © Jan and Jerry Sharpe - J&J Sharpe

Costs Jan and Jerry Sharpe estimated that overall, Furzedon was approximately 3 times more expensive than a traditional build. Due to the nature and the materials, time taken was a major factor.

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