We consider the advice that "the tongue and groove are brought tightly together by using a ch

A reference in our library (CSIRO Division of Building Research Special Report, Low-Rise Domestic and Similar Framed Structures Part 5) makes the point that in the case of strip flooring "the concentrated loading is the critical design consideration....not the uniformly distributed load".

We assume the pergola won't have a roof in which case oregon isn't highly recommended for weather exposure. Australian Standard 5604, Timber - Natural durability ratings, places oregon in Durability Class 4 with a "probable" above-ground life expectancy of up to 7 years. A paint coating may prolong the life of the timber if well maintained on all surfaces, but if the paint breaks down, allowing water to become trapped under the coating, it can have the reverse effect of hastening deterioration.

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.