I have what I believe to be balau decking in my place. I was told (by builder who installed it 5 years back and has it himself in the same block of flats wher he lives) that the wood needs no maintenance. It should be allowed to fade - part of the look. I've also been told that using something on it may be a bad idea. I'm not mad on the faded look but I can live with it. But I have contradictory advice. I was going to use something like Jotun Demidekk which on person saud would be good - I've also seen advice to use an oil like Osmo. Advice please.
Balau does not accept treatment too well. It is, as you say, designed to fade and most people put up with the slightly grey finish that results.....However, we dont believe this is best for the timber and always treat ours with oil (Varnish should NEVER be used on Balau) the oil we use is here but lay it on with a brush and brush it in well. If it puddles up, brush it out. Balau will not accept a ot of oil so be gentle with it. https://www.diydoctor.org.uk/DIY-superst ... litre.html