Magna:
Yours is a notoriously responsive builder. You should call them and find out what the original finish is, and what they recommend for maintaining it.
Without that inside information you will be left to experiment to find what works best.
Ours was 14 yrs old on purchase. The teak had never been refinished, so still had its original oil finish. That was well weathered, bleached by the sun in places, marked with water stains where the window had leaked, so all of it needed work.
Over the years, some products failed to deliver, others work very well.
Tried and rejected: water based Varathane, stained when wet, hard to remove. Oil finishes, always have that "needs another application" look.
Tried successfully: oil based varnish, several different brands, but the phrase "you get what you pay for" certainly applies. Varnishes intended for outdoor use are also better inside, though they sometimes go on darker than those intended for interior use, to I use them where weathering is likely and the interior kind where there will not be a likelihood of weathering.
