Haven't visited this thread in a while and just saw your question regarding the deck for Bismark.
The reason for wooden decks on WWII battleships (and submarines, U-boats and other warships too) was to make the decks less slippery when wet or in icy conditions. There's just no way to make steel decks non-slippery and not have whatever coating they put on them not wear off in the hard use the navy puts them to.
Therefore, to be less slippery, they do not put any varnish or other coating on the decks, but leave them as bare wood. In fact, in the old days, it used to be a daily job of sailors who needed for other duties to get onto their hands and knees and scrub the decks with pumice stones to scrape off anything on the deck (like oil or paint) and roughen up the surface to make it more non-skid.
The favourite wood to use was teak, because it's hard and extremely durable under almost conditions, but if teak wasn't available, other woods such as oak might be used. Soft woods, like pine were not liked because they wore out too quickly and broke too easily under hard use.
Because the decks aren't varnished, they often turned grey undless they were constantly sanded/scraped, but this takes a couple of years so most would still look like raw wood except in corners where there wasn't much foot traffic.
If you buy a scribed board to make your deck out of, as TRM says, try to make some planks lighter than others to give an impression of different boards. Keep in mind there's a specific pattern of joints on a ship's deck, thery're not random like a back yard patio. The pattern is called "5-step butt planking", and is used because it's the strongest pattern by keeping the joints as far apart from each other as possible.
20 feet is the standard length of most deck planks.
There are also several different ways of finishing off the edges where the wood deck joins the hull called "joggling" since planks cannot come to a point, it's too weak. The ends are nipped off when the planks get's to be only 1/3 the full width making a sort of zig-zagged edge.
Smaller ships, like destroyers and corvettes didn't have wood decks except in small areas around the bridge because it was felt that in rought weather, it was too dangerous for crew to be on deckm but U-boats and subs of course were another matter since even in calm weather the decks would be wet.
If you want any help with the various deck patterns, drop me a line and I'll try and help. There are several other specifics for wooden decks as well, but the stepped butt planking and joggling are the two main patterns that would be obvious at that scale.
