Timber is a widely preferred building material in the Australian residential construction industry, due to its ecological sustainability, low embodied carbon, low weight, and affordable economic cost. Structural sawn timber is Australia’s primary residential construction material resource, being widely used for lightweight timber framing. However, a rapid recent increase in construction demand has seen a severe shortage in the available supply of seasoned sawn timber. This thesis aims to develop knowledge and strategies that enable better use of low structural grade (F-grade) sawn timber in timber residential building construction, for improved utilisation of structural boards available from Australia’s current plantation stock. Two objectives were set to address the thesis aim. The first objective was to improve the design tables in AS 1684 to allow for substitution between high structural grade timber and low structural grade timber. This was achieved with the development of a novel parametric design framework for creating structured and indexable span data sets, from the decoupled evaluation of structural member capacities and building design actions. The framework was implemented for five timber wall frame element types, with generated data verified against existing span table data published as supplements to Australian Standards for residential timber-framed housing. The developed framework and digitised span data were then used to investigate how span capacity is influenced by revisions to building practice and to develop alternate AS 1684 span tables formats that facilitate cross-grade comparison, minimum-grade specification, and computational tool integration. The second objective was to optimise or vary the mixture of timber grades used within wall frame construction based on available market supply across all grades. This was achieved with the development of a framework for estimation and optimisation of resource consumption for five types of common studs in timber wall frame construction. The framework fist established a house topology database by extracting timber house classification and geometric data from local council development approval data. Timber wall stud sizes and construction volumes were then estimated for all selected grades, by indexing house design parameters to the digitised span tables from the preceding study. The best timber wall design options were then selected for three optimisation criteria, for minimum timber volume, minimum timber cost, and minimum difference between timber grade supply and consumption. The high timber cost incurred when matching the timber grade supply and consumption can be reduced by introducing additional supply of low structural grade timber during the substitution of high- and low-structural grades of timber. Findings of this thesis can to help reduce over-specification of wall studs and mitigate potential timber shortages, by improving the utilisation of low structural grade timber within timber wall frame construction.