Developed in-house at Airey Taylor Consulting, the ClayLock foundation system was patented in October 2005.
A Breakthrough Foundation System for Australia’s Reactive Clay Soils
ClayLock prevents damage to low-rise housing; community, institutional and commercial buildings; rail, road and other civil works built on reactive clay soils.
Conventional foundation design for reactive clay soils resists movement, particularly differential movement across concrete slabs. Despite the best efforts of the engineering community and approximately $315 million per year spent on foundational stiffening, cracking remains is a serious national problem. A 2005 study of 75,000 houses surveyed by Archicentre in Queensland found an astonishing 38% were cracked, with structures on vulnerable sites nationwide requiring expensive remediation and even replacement.
ClayLock is the first significant advance in clay-related foundation design since the 1970s, when Australian researcher Dr John Holland s world first research pre-empted the current design code (AS 2870 : Residential Slabs and Footings Construction). It contributes significantly to the international body of knowledge on foundation design.
Instead of resisting the movement of clay reactive soils, ClayLock utilises their natural forces to create soil stability for each construction and remove the need for complex footing or raft structures. The technique involves:
- Using a durable polyethylene membrane to extend the footprint of the building and protect the foundation slab from seasonal edge effects; and
- Accelerating the soil condition to its maximum moisture content beneath and around the slab during the first stages of construction
- Locking the moisture content under the polyethylene at a permanent level of moisture and prevent seasonal swell
Polyethylene plays a key role as it prevents moisture escape in either liquid or gaseous form. A durable form of polyethylene with strict quality controls and around 50 times the vapour barrier performance of standard construction polyethylene has been sourced by Airey Taylor Consulting for this purpose.
Acceleration of moisture content is via a single irrigation beneath the newly cast slab and into the encapsulated extended footprint area. By doing this the clay, mound, or dome usually encountered after years of moisture equilibration becomes the stable state under workable timeframes.
Advantages of Claylock
- Prevention of structural damage and cracking due to movement of clay soils
- Practical, robust and self maintaining over full course of the structure’s life
- Construction savings over present methods are around 40%
- Ease of construction leads to ‘critical path’ cost benefits in time/schedule acceleration
- Environmentally advantageous though net concrete/steel saving; no use of chemicals
- Elimination of annual maintenance expenses
- Elimination of expense related to failure processes involving dispute, litigation, remediation or demolition and rebuilding
RetroClay addresses repeated, ongoing damage to buildings initially constructed with inadequate footings on clay based soils.
This unique system represents a first class example of the interaction of the structural and geotechnical disciplines of engineering to achieve a technically sound, highly cost effective and socially desirable solution.
In 1995, Airey Taylor Consulting began development of an advanced foundation remediation system which retrospectively addressed repeated structural damage due to initial construction on inadequate footings on clay based soils. This unique “Retroclay” system was awarded a prestigious Certificate of Recognition in 1998 by the Association of Consulting Engineers Australia for Excellence in Engineering.
Retroclay® (now registered) represents a first class example of the interaction of the structural and geotechnical disciplines of engineering to achieve a technically sound, highly cost effective and socially desirable solution.
The system works by extending the footprint of the clay damaged structure or structures and then irrigating the clay mound beneath it to its maximum seasonal swell. Repairs can then take place to the permanently stabilised structure.
Advantages of RetroClay
- Implementation is retrospective.
- Implementation requires minimal specialist skills, little equipment and uses readily available materials.
- It is highly cost-effective in contrast to expensive and often unsuccessful methods such as underpinning of footings.
- It has wide application in many parts of Australia where, due to the arid climate, seasonal variation of moisture within clay soils can cause movement around the perimeter of a building, resulting in cracking of walls and damage to finishes.
- It addresses the commercially damaging effect of degradation where properties have become either unsaleable or unable to be leased, with conversion to an aesthetically pleasing and acceptable appearance of the structure and internal finishes.