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A 1980s bungalow transformed with hemcrete and a green oak

extension.

Norlands was originally a 1980s bungalow, conventionally built from concrete blocks and clad in stone. It was expanded in 2010 by adding a second storey using hemcrete – a mixture of chopped hemp with lime – a successful and extremely unusual marriage of conventional and innovative materials.

Introduction

Truro

ExeterCrackington Haven

Norlands

Key Dates Construction of the original bungalow : 1987Planning approval : July 2009Designs : August 2009Building control approval : December 2009Construction : January to Décember 2010

Entrance - Photo © Paul Teague

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ContextPaul Teague is a builder by trade and he built Norlands in 1987, when he and his wife were recently married. By 2009, Paul’s family had outgrown the original bungalow and he was ready to expand – this time with the help of his son Josh. The family building firm, TH Teague & Sons, frequently works with historic buildings and this had sparked an interest in lime, hemp and green oak.Paul’s aims were to expand the family’s living space, creating additional bedrooms, a larger kitchen and family room. He wanted to use natural materials that would create a pleasant, healthy environment and make the house

more energy efficient. Importantly, the additions to the bungalow needed to create a unified design incorporating the old and new parts of the house. Architect Mark Kemp succeeded in creating a coherent and pleasing design by using a natural slate roof which bridges both storeys on part of the main elevation, a unified window design and careful detailing. As architect and client/builder, Mark and Paul formed a rewarding partnership as they were both motivated to innovate in their use of natural materials.

Plan © Parkes Lees Architects

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French-British collective Libnam3

Building overviewThe original bungalow at Norlands was of cavity wall concrete block construction on concrete strip foundations, with stone cladding. These elements were retained, with the original tiled roof being removed and the cavity closed off with blocks. The hemcrete second storey was built within a timber frame on top of the existing walls and finished with an exterior lime render. The new second storey incorporates three bedrooms and two bathrooms. A green oak extension on the rear

elevation of the house provides an enlarged kitchen and dining area. Hemp has excellent insulating properties and this, plus the addition of solid foam insulation boards in the roof has dramatically improved energy efficiency. The house was previously heated using an oil-fired boiler serving radiators. The main heat source is now a wood burning stove which has been added to the new kitchen/dining room, with the oil-fired boiler being used less frequently. The house is now more comfortable, retains heat more effectively and uses less oil than before the extension was built.

Green oak frame of the extension - Photo © Paul Teague

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Technical focus : Using hemcrete to extend a 1980s bungalowPaul chose to use hemp because he had previously used hemp renders on historic buildings. He had heard about the use of hemcrete from local expert Chris Brookman of Back to Earth Natural Building Solutions and was keen to use a natural material for his home. In addition to their insulating qualities, hemcrete and lime render were also chosen as being beneficial to the timber frame of the building due to their breathability. Cornwall Council

were supportive of the project, the building control officer in particular being keen to see the innovative use of hemcrete in this context.

Easy to use and self-insulating Hemcrete was used to construct the upper storey walls within a timber frame using shuttering to hold the material in place as it dried. The method was effective, one of the benefits being that it could be moulded around all the details of the building to create very effective insulation; the hemcrete was packed in to fill all voids and eliminate cold bridging. Paul found this easier

Hemcrete hemp and lime filling - Photo © Paul Teague

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Barriers and solutionsCoping with the Cornish climate - againThe hemcrete was covered with natural lime render, which was left unpainted. Norlands sits in a fairly high and exposed position near the north coast of Cornwall and the most exposed part of the house is the west-facing gable end, which takes the brunt of prevailing wind and rain. In early 2014, following an

and more effective than the rigid insulation materials he has used on other buildings.

Paul’s son Josh worked with the hemcrete and found the process easy and quick. The hemcrete was supplied dry and mixed with water and Tradical lime on site to the correct consistency – some trial and error was required to perfect the mix, but this was the only technical difficulty encountered. Another advantage was that small quantities could be lifted onto the second storey, avoiding the need to lift heavy materials such as concrete block.

Coping with the Cornish climateA key element of the process was

that the entire house was covered to make it watertight during the construction, this was essential to allow the hemp to dry, particularly in the damp Cornish climate. Paul considers that the build would have taken much longer if the building was not covered. The product used was Tradical hemcrete.

Hemp and lime insulation- Photo © Paul Teague

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exceptionally wet and windy winter, the lime render over the hemp on this gable was showing some signs of green mould. In response to this, Paul has painted the render with Beekosil breathable paint system supplied by Cornish Lime Co which will offer greater protection while allowing the lime render and hemcrete to breathe.

The drying time and need to protect hemcrete during construction is a potential barrier to its greater use in Cornwall and other damp areas; both factors will add time and expense to a building project. For a self-builder working primarily with unpaid labour this might be less of a problem than for a conventional build.

The role of architects and contractors in promoting the use of natural materialsMark Kemp of Parkes Lees Architects designed the Norlands extension; he observed that many clients would like to use natural materials but are put off by additional costs. One problem which contributes to this is that, since many building contractors are unfamiliar with the use of these materials, their bids for work will be artificially high because they are unable to confidently bid at a reasonable price. Mark has found that when he recommends certain materials, builders will sometimes discourage clients from using them. He considers a builder

Wood stove - Photo © Paul Teague

StakeholdersClient : Paul TeagueMain contractor : self-build with help from TH Teague & SonsArchitect : Mark Kemp, Parkes Lees Architects, Launceston, CornwallSupply of hemp and lime render : Back to Earth, Devon (including advice from Chris Brookman)Green Oak supplier : Hewins Timber, Oak specialists, SomersetOther contractors working on the project : M Biddick and Sons, Electrical worksGWT PlumbingBirma-Blast, Oak sand blasting,“Pete the Plasterer” Lime renderingGeneral building materials, RGB, Launceston.BEEK paint supplier and advice, Cornish Lime Co

Costs Hemcrete, renders, racking board and mesh : £6,000 Green Oak : £2,400Green Oak glazing : £1,800Replacement windows : £9,600Ceramic tiles : £1,200 Mineral paints for interior : £540Scaffolding : £6,000Complete re-wire : £9,600Complete re-plumb, central heating, Solar Thermal panels and sanitary ware : £16,800Rayburn and wood burner : £8,400Kitchen : £7,800Labour & general building materials : £49,860TOTAL (inc VAT) : £120,000

like Paul Teague to be unusual in his willingness to use a wide range of new and alternative materials

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and his interest in learning new techniques.

Cut plane © Parkes Lees Architects

ContactCornwall Sustainable Building Trusthttp://csbt.org.uk/