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The following technical information is also available for
download as a PDF file here.
Stabilised rammed earth (SRE) can successfully be used to
conform to the Building Regulations (2000) for England and
Wales as an acceptable alternative form of low-rise masonry
construction in public and residential buildings. Recommendations
for how this can be achieved are given through the case
study by the Planning Department of Chesterfield Borough
Council (ref: Hall, Damms & Djerbib, 2004).
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Regulation 7 - Materials
and Workmanship |
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At
present there are no officially recognised codes of practice
for rammed earth construction in the United Kingdom. The
fitness of SRE materials is currently established under:
a) Tests and calculations, and
b ) Past experience
Suitability and classification of soil materials is established
in accordance with:
BS 1377-2: 1990 - Soils for Civil Engineering Purposes - Part 2: Classification Tests, British Standards Institute, London
BS 1377-4: 1990 - Soils for Civil Engineering Purposes - Part 4: Compaction Related Tests, British Standards Institute, London
.
A series of 100mm SRE cube samples are produced in a laboratory
using the prescribed mix design in accordance with the guidelines
prescribed in:
Hall M and Djerbib Y, 2004b, "Rammed Earth Sample
Production: Context, Recommendations and Consistency",
Construction and Building Materials, 18 [4] pp.281-286.
N.B. Based upon BS 1881 for concrete materials
.
The curing shrinkage and estimated construction tolerances
are calculated based upon:
BS EN 772-16: 2000 Methods of Test for Masonry Units
- Part 16: Determination of Dimensions, British Standards
Institute, London
.
Cube samples are tested for compressive strength in accordance
with the guidelines prescribed in:
Hall M and Djerbib Y, 2004b, "Rammed Earth Sample
Production: Context, Recommendations and Consistency",
Construction and Building Materials, 18 [4] pp.281-286.
NB Based upon BS 1881 for concrete materials.
Cube samples can also be tested for other physical properties
depending upon the application, e.g. moisture absorption,
acoustic, thermal etc.
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Approved Document A - Structural Stability |
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For
the purpose of assessment under Part A (structural stability)
of the Building Regulations, SRE walls can simply be treated
as a high density mass walling element.
Test Specimens
All SRE test specimens are characterised and produced as
100mm cube samples using the methodologies proposed by Hall
M & Djerbib Y, 2004, "Rammed Earth Sample Production:
Context, Recommendations and Consistency",Construction
and Building Materials, 18 [4] pp.281-286.
Compressive strength
Minimum characteristic unconfined compressive strength (f
'cu) = ≥ 3.5 N/mm2 Typical range of f
'cu =3.5 N/mm2 to 12 N/mm2. N.B. The f
'cu can be increased by altering the soil
grading, the cement content, the ramming and the curing
procedures.
Density
Typical dry density (ρd) = 2000
to 2100 kg/m3 (at 98% of Proctor compaction) Tested in accordance
with BS 1377-4: 1990 - Soils for Civil Engineering Purposes
- Part 4: Compaction Related Tests.
Fixing capacity
300mm Hilti C10 epoxy holds 2,000kg pull, Amdel Report No.
M1034/87.
For further details of compliance please refer to:
Hall M, Damms P & Djerbib Y, 2004, "Stabilised
Rammed Earth (SRE) and the Building Regulations (2000):
Part A – Structural Stability", Building Engineer,
79 [6] pp. 18-21
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Approved Document B - Fire Safety |
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SRE
is classified as a "non-combustible material".
Fire resistance rating = 4 hours.
Tests performed by CSIRO Report No. 1839.
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Approved Document C4 - Resistance to Weather and Ground Moisture |
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SRE
walls are constructed using standard practices for DPC &
DPM installation
Experimental testing has revealed that SRE easily conforms
to the Building Regulations in this country;
Hall M & Djerbib Y, 2004, "Moisture Ingress in
Rammed Earth: Part 2 – The Effect of Particle-Size Distribution
on the Absorption of Static Pressure-Driven Water",
Construction and Building Materials
Water Absorption Properties
Pressure-driven moisture absorption:
Initial surface absorption after 10 min (6% cement content)
= 1.90 to 9.95 ml/m2 sec
Capillary absorption:
Typical Sorptivity (S) value = 0.251 to 1.631 mm min-0.5
Initial rate of suction (6% cement content) = 0.29 to 1.47
kg/m2 min (Compare with conventional materials using graph
below)
Graph: adapted from Hall M & Djerbib
Y, 2005, "Moisture ingress in rammed earth: Part 3 -
Sorptivity, surface receptiveness and surface inflow velocity", Construction
and Building Materials. |
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Durability Properties |
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Durability
of SRE materials is determined using the 'accelerated erosion
test' (AET) in accordance with Standards New Zealand, 1998,
NZS 4298: 1998 Materials and Workmanship for Earth Buildings,
Wellington, New Zealand
AET value for SRE = 0.0 mm/min
Tests performed by Materials Consultants Aust. Pty. Ltd.
Report No. 202/87
Please note: Unstabilised rammed earth
walls may not be compliant under Building Regulations.
Both Regulation 7 and Approved Document C categorically
state that external masonry walls on a building must:
Not
be damaged by rain or snow
Resist the passage of rain (or snow) to the inside of
the building
Not transmit moisture
due to rain (or snow) to another part of the building that
might be damaged |
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Approved Document E - Resistance
to the Passage of Sound |
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In
order to demonstrate compliance "laboratory values
for new internal walls and floors within: dwelling-houses,
flats and rooms for residential purposes, whether purpose-built
or formed by material change of use" must have a minimum
Rw of 40 dB (Rw = weighted sound reduction index)
Example: an SRE wall; Assuming a wall thickness of
300mm the typical Rw of the wall = 58.3 dB |
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Approved Document L1 - Conservation
of Fuel and Power in Dwellings |
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SRE buildings can be assessed either using the target U-value
method, the Carbon Index method or the elemental method.
The walls can be constructed in 3 different Part L-compliant
configurations:
1. Solid SRE wall with external insulated cladding + render
2. Solid SRE wall with internal dry lining
3. Cavity SRE wall with solid-foam cavity insulation
Example:
For a cavity SRE wall with 175mm SRE inner & outer leaves
incorporating polyisocyanurate solid cavity insulation and
stainless steel wall ties;
Calculated U-value = 0.335 W/m2 K (for 50mm thick insulation)
Or, = 0.245 W/m2 K (for 75mm thick insulation)
SRE walls also have very high thermal capacitance (i.e.
"thermal mass")
Typical value for a 300mm wall = 1673 KL/m3K
Approximate thermal time lag = 6 - 8 hours |
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