This part of SABS 457 specifies requirements for preservative-treated softwood poles, droppers, guardrail posts and spacer blocks. The poles are intended for the erection offences and vine trellises, for general use in orchards and for structural purposes. The droppers are intended for fencing. The posts and spacer blocks are intended for the erection of steel guardrails at the sides of roads.
Timber used in ground contact and exterior above ground contact, should have an expected lifespan of at least 20 years when treated in accordance with the requirements applicable to the exposure classes (see table 3). Timber treated for interior above ground exposure class should have an expected life span equal to that of the structure it is used in.
NOTE 1 Except under the certification mark scheme, assessment of compliance with the requirements of 5.2 to 5.6 (inclusive) and, except in the case of units treated with creosote or a creosote and waxy oil mixture, 4.4, requires special agreement between the supplier and the purchaser.
NOTE 2 Steps should be taken to prevent the "mushroom top phenomena" (cutting of wire into the pole) in poles to be used as straining poles, as in vineyards.