Unfortunately no timber is classed as 'non-combustible' when tested to Australian Standard 1530 Part 1: Combustibility test for materials. The test involves placing specimens in a furnace at approximately 750°C, at which temperature they must produce only a limited amount of heat and flame.

If the house at Dromana is a holiday house, closed up and unoccupied for long periods, the moisture content of the timber is about right at 12-15%. If it is continuously occupied year round, and heated and/or air conditioned, ideally the timber should be a little drier. The wall framing will be OK - pine framing is classed as 'seasoned' at 15% or less. However, the flooring may undergo some changes if subject to further drying.

We would hesitate to call any varnish coating 'permanent' when applied to exterior timber, unless protected from the weather. Varnishes form a skin which tends to become brittle with age, causing cracking and peeling. Some varnishes perform better than others, but are best applied to new wood. Weathered wood leads to poor adhesion of the coating. For your weathered jarrah deck we suggest a deck cleaning product, followed by decking oil. Such finishes are easy to apply, and easy to maintain when re-coating is necessary.