We assume there are no internal linings contributing to the thermal performance of the cabin and the 70 mm wall boards are exposed internally and externally. In that case the thermal resistance of the walls (R-value) is just the R-value of the timber itself. CSIRO quotes an R-value of 0.25 m².K/W for a 25 mm thickness of radiata pine, ie. 0.01 per 1 mm thickness.

Regarding the splits in the glulam, there must have been a change in moisture content. It’s unclear whether the product was shipped at a moisture content higher than ambient, and dried on arrival – equilibrium moisture content is 10% to 12% indoors in Sydney. Some European glulam is supplied with a moisture content up to 16%. It would be interesting to test your glulam with a moisture meter, preferably the more accurate needle type.

For a truncated girder in a hip end, span by station divided by 4 will give you pretty much the total area supported. However, note that there will be a small area of roof beyond the girder truss where the top chord of the jack truss and adjacent trusses are extended and bear down onto the girder truss. Figure 2 in Gang-Nail Guide Line no. 4 will help to explain this. The Guide Line can be downloaded via this link https://www.mitek.com.au/wp-content/uploads/2021/05/GN-Guideline-4.pdf.