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Technical information



  • BLOCK DIMENSIONS; One full-sized block equals 600 mm long X 300 mm wide X 300 mm thick. (2 x 1 x 1 foot)

  • WALL AREA; One square metre of wall equals 5.5 blocks, One block equals 0-18m².
  • EARTH QUANTITY; One cubic metre of earth will produce approximately 18 blocks. One full block equals 0-054m³. 
  • CEMENT QUANTITY; a usual earth mix of one part cement, to nine parts earth. One 20 Kg bag equals two blocks.  

Building considerations

  • STRUCTURAL RATING; The FORMBLOCK system will produce load bearing walls, with foundations of strip footing or slab floor generally specified for double brick construction. Seek expert advice for specifics for your application.

  • FLEXIBILITY OF DESIGN Although blocks are based units of 300 millimetres (one foot), walls of any length can be produced. Along with any door or window configurations. It is also possible (for experienced users) to produce corners with non-square angles. (More information) 

Hexagonal hut, Upper Mebul, N.S.W. Window frames set into wall as it progresses. Leura N.S.W.

( click to enlarge) 

Adobe mud bricks used in conjunction with FORMBLOCK to form arch, Piha New Zealand Curve wall constructed Ellerslie flower show 1996, Auckland New Zealand.

  • SERVICES: Electrical wall boxes with sweeps attached can be simply cast in place when pouring earth, flush with the face of the shutter board. Access for plumbing through walls can also be easily cast during wall production.

Electrical conduits and water supply cast into wall as produced.

( click to enlarge) 

  • CONTROL JOINTS are usually required to be placed in long walls made of earth (generally every 4 metres, or under windows). The amount of expansion and contraction of walls is related to both the earth used, and the design of the structure and is a normal property of earth construction. If unsure seek expert advice.

  • COUNCIL BUILDING REGULATIONS in regards to the FORMBLOCK method, which will be the same as for earth building in general, can vary from district to district. In most cases, councils in Australia may require sample blocks to be tested by industry authorities such as the C.S.I.R.O. and an engineer to certify the design of the structure. 

 C.S.I.R.O. Certificate of Test. A Queensland university of technology, Certificate of test page 1 a Queensland University of Technology, Certificate of test, page 2.

( click to enlarge) 

   FORMBLOCK blocks made from the stabilized earth of 9:1have had no problem being certified by these authorities.

  A history of earth building in your area can give you an indication of the chances of you project being approved.


Materials that can be used

EARTH required for use in FORMBLOCK’s method of earth-wall construction is quite sandy containing a low ratio of clay. (In fact, you can actually use 100% friable sand.) Soils with high levels of clay can be corrected by mixing in sharp sand.  

  • An evenly graded ‘sandy loam’ preferably with no more than about 10% clay. Also decomposed granite soils.
  • It should be free of any organic matter (such as humus, or top soil.)
  • Aggregate no larger than about 70 mm (large stones can cause cracking.)
  • Water should be potable (drinkable and free of salts).
  • Cement ,5% to 10% general purpose cement is usual, however on site testing is advisable.
  • There are 3 main tests; shrinkage, compression and accelerated erosion tests. The latter 2 should be carried out by a recognised authority, however it is desirable to do shrinkage tests of you own when selecting suitable earth. For this refer to‘ The ‘Earth Shrinkage Test Guide’. Seek expert advice if you remain uncertain about the suitability of the earth you wish to use . 
  • A good guide to suitable material can be found in the C.S.I.R.O.'s "Earth-wall Construction"  Building Technology File 06 www.publish.csiro.au/nid/18/pid/2981.htm


CONCRETE in all its forms can be used in FORMBLOCK’s method of wall construction with or without aggregates, and with cement content of no less than 12%.


Earth or Concrete?

CONCRETE should be used for the following building situations;

  • All sub floor walls sections below damp-course level. 
  • To bring walls to an even level before continuing the walls further in earth. (an earth wall constructed on a sloping footing for example, can settle unevenly resulting in problematic cracking.)
  • For retaining walls, whether in a building wall or landscaping.
  • All lintels, consult your engineer for your lintel specifications as they can be wide and varied.
  • Further general information regard cement and concrete. www.concrete.net.au/publications/pdf/concretebasics.pdf   www.cement.org/basics/concretebasics_faqs.asp

EARTH can be used in the following building situations;

  •  The use of cement stabilized earth is generally acceptable for constructing load bearing walls once the concrete sub floor wall are complete, ( the stabilized nature of the earth used in Formblocks method will certainly cope with incidental exposure to falling rain, however constant exposure to dampness, from pavement splash, or poor roof drainage may cause problems in the long term.)
  • Avoid slim earth columns or pillars, FORMBLOCK recommends columns of 900 mm x 300mm wide, but once again seek expert advice for the suitability of the columns application.


How much wall can be done in one day?

*Based on persons of AVERAGE fitness, and assisted with a powered cement mixer.

  • ONE PERSON could comfortably accomplish a course of blocks between 6 to 12 metres (40 feet) long.
  • TWO OR THREE PEOPLE could accomplish a course of blocks around the perimeter of an average 3 bedroom home.
  • THE NEXT COURSE of blocks can be produced the following day,  a 2.4 metre (8 feet ) high wall would take 8 days.)

CLEANING FORMBLOCK formwork is easy with just a quick scrape, or wire brushing.


© Copyright FORMBLOCK Australia Pty Ltd 2001 A.B.N. 85 072 393 956.