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hedra_home_owners.jpgWe are currently building the resources for this page, however please feel free to download any of our public documents. Reading these will enhance your understanding of the interaction between soils, footings, gardens, trees and rainfall and how your house is currently performing

This is a Queensland government organisation (formerly the Building Services Authority) and their webpage is a vast resource for home owners whether you live in Queensland or other states or territories.
Their “Home Maintainance” page which can be accessed by clicking here is of great importance to all home owners as is the QBCC ‘Subsidence page’ which can accessed by clicking here

This latter page has has two(2) documents which all home owners (wherever they live) should download and read, and they are:

  • A home owners guide to subsidence and acceptable tolerances specified in AS2870*
    *AS2870 in its current form is known as AS2870-2011, which is the Australian standard for ‘Residential Slabs and Footings’
  • A simple “how to” guide to preventing structural damage to your home.

About AS2870:

The current version of AS2870-2011 contains 174 pages. Home owners are not expected to own or read this document, but need to know it exists.

Since 1986, AS2870 has been a referenced document in the ‘Building Code of Australia’ and consequently is the ‘bible’ for Builders, certifiers, site classifiers, structural engineers and others.

Amongst other things, AS2870 covers:

  • The classification of a building site, with respect to the soils and existing/nearby features and mainly how the soils will perform with changes in soil moisture.
  • Site drainage before and after construction.
  • The design of the various structural elements from th footings and slab upwards.
  • Storm and effluent water disposal
  • The influence of trees and other factors which can adversely affect soil moisture and hence footing performance.

Home owners should also be aware that compliance to AS2870-2011 does not ensure a crack free/distress free dwelling and this is clearly explained in the above referenced QBCC documents.

Constructing a crack free/distress dwelling is achievable by using more substantial footings, which depending on the soil conditions of a specific site, can cost what most future home owners find is an unrealistic high cost.

We recommend that any home owner who wishes to explore this crack free/distress free option, that they talk to both their builder and his structural engineer prior to signing any contracts.

Since 1986, well in excess of 1 million houses have been built across Australia using the principles of AS2870, and providing that the following is done, the performance of the houses has been more than acceptable.

  • The onsite soils are correctly classified.
  • The footing system is appropriate for the soil conditions.
  • Stormwater disposal and effluent disposal pipes are laid to a realistic grade for the soil conditions this is not very well enunciated in either AS2870 or AS3500 but is very important to ensure a positive and adequate flow is maintained, and this is best specified by an engineer with a sound knowledge of hydraulics and soils. Futhermore these pipes must have mechanical/expandable joints as required in AS2870-2011.
  • The builder and his contractors who construct your house, faithfully reproduce the design.
  • The builder and his contractors successfully manage onsite drainage from commencement of earthworks, to handover.

After handover the owners not only maintain the good site drainage, they must ensure:

  • Landscapers, swimming pool builders and any other contractors who may work on the property post hand over ensure that the site drainage if interfered with, is re-instated as part of their works before they leave the site.
  • Any plumbing and drainage pipes which become broken must be promptly repaired
  • The planting of trees and shrubs by the owners must consider the soil conditions, and in most cases these plantings do have the potential to adversely affect the performance of the footing system, there for a prudent owner should plan out the type of garden they envisage and prior to signing a contract with a builder, ensure that the structural engineer is comfortable that his design can cope with the gardening/landscaping proposal.
    ‘HEDRA’ building and maintaining your house document


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