Left to weather your garden structure will turn a beautiful silver-grey. If you choose to let it weather down then we would still recommend treating your structure annually with a water repellent.
You may decide to paint your structure rather than leave it to weather naturally. Like the images shown. If this is your preferred choice then we advise our customers to follow the manufacturers guidelines for care and re-painting in the future.
Your structure could also be treated with a clear outdoor varnish, we use Ronseal Crystal Clear, like the first image in this post.