Bearers and joists
Sizes and grades for bearers and joists are shown in the left hand column of Tables 3, 4 and 5. Sections of greater size omitted from the tables may still be available upon enquiry with individual producers. This includes sections wider than 100mm wide and F22 stress grades (seasoned or unseasoned). Producer's names can be sourced in the Producers Guide referenced at the end of this document.

Large bearers may require 'heart-in' which means the tree pith and surrounding juvenile wood are included in the centre part of the bearer. AS2082 (see note 2)‚ permits the heart in the central 1/9th of the cross section, but only on sections 175 x 175mm or greater in size. Caution is required with 'heart' material as it is subject to heart shakes which are longitudinal fissures within the wood which weaken large sections. One option to reduce the problem is to use high density timbers with relatively low shrinkage rates, e.g. red ironbark. These timbers are very strong and create less internal shrinkage stresses, thus reducing heart shakes. Another option is to reduce end-grain splitting and moisture loss by coating the ends with a suitable sealer immediately after sawing. In addition, all sections should be end-plated with multi-toothed plate connectors covering at least 50% of the exposed end sections. Timber should be specified with these features in place, prior to delivery.


Note
1. AS2082 - Timber - Hardwood - visually stress-graded for structural purposes, Standard Australia, Homebush.