SNZ - NZS 4297
Engineering design of earth buildings
|Publication Date:||21 February 2020|
The scope of this standard is limited to unfired earthen wall building materials defined herein as adobe, pressed brick, cob, poured earth, in-situ adobe, or rammed earth and which contain clay and silt and which largely rely on the clay particles present to achieve satisfactory performance with or without chemical stabilisation. Earth building materials to which this standard applies shall comply with NZS 4298.
This standard sets minimum criteria. Parties are at liberty to set higher standards for any matters referred to in this standard.
Earth construction in accordance with this standard shall not exceed 6.5 m in height from the top of the foundation to the top of the earth wall.
The air dry density of earthen materials shall be from 800 kg/m3 to 2200 kg/m3.
Design using procedures or material properties not described in this standard may be carried out when it can be shown by one of the following methods that the elements so designed have adequate performance at the serviceability limit state and at the ultimate limit state:
(a) A special study;
(b) Experimental verification;
(c) Rational design based on accepted engineering principles; or
(d) Verified service history.
Aspects of designs which rely on any of (a) to (d) above are outside the scope of this standard as a means of compliance with the NZBC and will be treated as alternative solutions.
The purpose of this clause is to acknowledge new design practices and the use of newly developed material properties that may go further than this standard permits, provided that the acceptability of such methods or approaches can be clearly demonstrated by way of the options listed.
Building consent authorities will expect alternative design methods, material properties, and structural systems to be supported by one or more thorough experimental studies, or demonstrated service history.
Demonstrating compliance of alternative solutions with the NZBC will be required under the legislation that governs issuing building consents.
Cement as a stabiliser can contribute substantially to strength in mixtures with a high proportion of sand. Where strength is almost entirely reliant on cement or another stabiliser, the masonry standard or the standard appropriate to that material should be used.
This standard applies to earth wall items including house and building walls, boundary fences, outbuildings, isolated walls, footings, fireplaces, and any other items that may be subject to engineering design. This standard also covers components of any of the foregoing. Retaining walls are excluded from this standard.
This standard applies to New Zealand and its offshore islands.