It's hard to give you a definite answer because maintenance intervals for natural finishes (ie. those that allow the grain and colour to show through) depend on weather exposure. Also we haven't carried out any exposure tests that would provide comparative data. Cedar is a stable timber in the weather, not prone to warping or splitting, and takes a finish well. Decking oil, and oil finishes in general, will give good results on cedar and come in a range of colours.

Presumably the pipework to be suspended from the CLT floor is more or less of domestic size. If so, typical pipe hangers would utilize two coach screws to attach the hangers, with similar fixings required for suspended cable trays, ie. relatively small diameter fasteners.

The photos attached to your query don't look like typical fungal decay, although it's hard to be sure from viewing an image. The surface 'growth' actually looks more like the result of exposure to salt water - compare your image with the one on this site: https://www.researchgate.net/figure/Characteristic-damage-to-treated-wood-caused-by-salt-a-Treated-deck-boards-exposed-to_fig1_316317038.

There's a good explanation of acclimatisation of flooring in our Technical Design Guide #09, available for download free of charge via this link https://www.woodsolutions.com.au/publications - refer pages 33-35. Note that you need to have some way of knowing when the flooring has reached an appropriate moisture content, or perhaps it will already be at the right moisture content, in which case there is no need for lengthy acclimatisation. Either way, testing with a moisture meter will tell you when it's ready to install.

The images of your American oak flooring, sent separately, show brown stains in conjunction with 'checks' (fine surface splits). American red and white oaks are prone to developing checks during drying - fine checks may even appear during carefully controlled kiln drying. In our opinion the brown stains associated with the checks are tannin stains. However, tannin stains don't appear spontaneously, they occur when naturally occurring tannin is dissolved by moisture and brought to the surface.