Any exterior wood surface faces two threats, UV degradation and water damage.
Ongoing maintenance requirements should also be a consideration.
I have found that an epoxy coating followed by up to eight coats of exterior spa varnish returns the best balance of finish quality and longevity. Yes it takes a lot of work, but it is worth it in the long run.
or
You could go with the factory finish..linseed oil and lamp black...
Either way, you should coat the bottom and side edges of each board with POR-15 (several coats) to protect them from the elements.
BTW...Larry's kits are excellent...top quality materials and fantastic hand finishing.
