Comparing Stabilised & Unstabilised Rammed Earth

Stabilised Rammed Earth Qualities
Unstabilised Rammed Earth Qualities
Requires normally 6 or 7% cement as stabiliser when built
Does not use any stabiliser
Can be made from soil, quarry waste or recycled building rubble
Must be made from soil with a high clay content
Meets UK Building Regulations re water resistance and impermeability
Susceptible to water, does not meet UK Building Regulations
Insoluble, unaffected by immersion
Remains water soluble, hence will collapse if moisture rises above 13%. This could be from a blocked gutter, flooding, sprinklers, burst pipe or similar.
Unaffected by rain
Needs wide eaves and surface protection
Needs no exterior protection
Needs protection by cladding systems or regular coats of lime wash or render
Can incorporate insulation and meet UK Building Regulations for U value
Needs to have additional exterior or interior layer of insulation and cladding to achieve required U value
Benefit of high thermal mass is maintained
If interior insulation is used thermal mass effect is lost
Strength can be reliably specified between 3 and 10 Mpa
Much lower strength, usually ~1Mpa
Normally build walls 300mm thick
Normally 600-700mm thick
Does not need larger foundations
Needs larger foundations to support thicker walls
Does not need concrete ring beam for supported loads
Needs concrete ring beam for load bearing applications
High strength achieved quickly, 70% of full strength within 7 days
Slow drying means it can take up to 2 months to get near full strength
Very small amounts of shrinkage experienced as wall sets
As wall dries, significant and unpredictable shrinkage occurs due to high proportion of clay as binder
Accuracy to normal masonry wall building standards
Poor accuracy due to shrinkage and distortion
Fast building system. Walls for an average house take 5 to 8 days
Limited modern experience, bu appear to be 3 to 5 times longer
Can be fitted into a standard building design with little effect upon other building elements
Building design must be adapted to accomodate thickness and weight of walls and the need for wider eaves
Can incorporate steel reinforcing, lintels, etc. so windows, doorways and large openings can be formed in walls
Poor results with reinforcement. Only small openings possible
Unaffected by rodents or insects
Can become infested by rodents or insects boring into the earth
Extensive recent experience - database of hundreds of completed buildings available
Limited recent experience in unstabilised rammed earth building within UK - approximately 6 buildings

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Company No: 5104506