Un bungalow des années 80 réhabilité à l’aide d’un béton de chanvre et d’une ossature bois.

1. 36
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 : 1987
Planning approval : July
2009
Designs : August 2009
Building control approval :
December 2009
Construction : January to
Décember 2010
Entrance - Photo © Paul Teague

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Context
Paul 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
N

3. French-British collective Libnam3
Building overview
The 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
bungalow
Paul 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

5. French-British collective Libnam5
Barriers and solutions
Coping with the Cornish climate
- again
The 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 climate
A 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 materials
Mark 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

7. Stakeholders
Client : Paul Teague
Main contractor : self-build with help from
TH Teague & Sons
Architect : Mark Kemp, Parkes Lees
Architects, Launceston, Cornwall
Supply of hemp and lime render : Back to
Earth, Devon (including advice from Chris
Brookman)
Green Oak supplier : Hewins Timber, Oak
specialists, Somerset
Other contractors working on the project :
M Biddick and Sons, Electrical works
GWT Plumbing
Birma-Blast, Oak sand blasting,
“Pete the Plasterer” Lime rendering
General building materials, RGB,
Launceston.
BEEK paint supplier and advice, Cornish
Lime Co
Costs
Hemcrete, renders, racking board and
mesh : £6,000
Green Oak : £2,400
Green Oak glazing : £1,800
Replacement windows : £9,600
Ceramic tiles : £1,200
Mineral paints for interior : £540
Scaffolding : £6,000
Complete re-wire : £9,600
Complete re-plumb, central heating,
Solar Thermal panels and sanitary ware :
£16,800
Rayburn and wood burner : £8,400
Kitchen : £7,800
Labour & general building materials :
£49,860
TOTAL (inc VAT) : £120,000
like Paul Teague to be unusual in
his willingness to use a wide range
of new and alternative materials
7
and his interest in learning new
techniques.
Cut plane © Parkes Lees Architects
Contact
Cornwall Sustainable Building Trust
http://csbt.org.uk/