According to Australian Standard 2796, Timber-Hardwood-Sawn and milled products, Part 1: Product Specification, the tongue thickness for 19 mm hardwood strip flooring should be 6.0 mm for face nailed, double-dressed, off-centre milled boards, or 6.5 mm for face nailed, double-dressed, centre milled boards. The corresponding groove dimension should be 0.5 mm greater to allow entry of the tongue. 

It is unfortunate that the owner didn't keep a record of the type of treatment carried out on your house poles, but presumably it was a process that complied with the Australian Standard. Make sure stormwater does not discharge adjacent to the poles, particularly those around the perimeter of the house. Internal poles are generally in relatively dry ground. A simple test suggested on a US website is as follows: "Checking the pole at ground level should be done using a screwdriver with a 12-inch shank. Hammer the screwdriver 6 inches below ground level on the high side of the pole.

The span tables in AS 1684.2, Residential timber-framed construction, assume an upper storey floor load of 40 kg/m². However, various software programs allow you to input different floor loads.

We were pleased to hear of your very practical hands-on project. No doubt you will be using some kind of hardwood for your coffee table. With regard to sustainability, our Environmental Product Declarations (EPD's) provide helpful data. You can download them from our website via this link https://www.woodsolutions.com.au/resources/publications/environmental-product-declarations.

Unfortunately there are no CAD files for our Technical Design Guide #46. The worked examples are “general conceptual designs” as explained in the Introduction, and are provided to show how to calculate using various design inputs, rather than for use in real life scenarios where actual design drawings would be needed.

It's very difficult to say exactly how long it would take for your floor bearer to lose half its cross-section to wood rot. Although the bearer is hardwood, different types of hardwood have different levels of resistance to fungal decay. Some species are more resistant than others. We can say it would take more than days or weeks, and at least some months, possibly up to a year. Wood rot progresses more slowly when wood is wet intermittently in the open air, as opposed to wetting from a constant source of moisture in an enclosed situation, as in your sub-floor space.