KaleunVIIC

I hope this helps with your question. The information below is for the Type IX u-boats, but their should be the same for both classes of boats.

East Prussian scotch pine (Kiefer) wood decking is employed on the superstructure deck except at the ends of the vessel, and on the bridge.  Wooden gratings are provided for installation in the battery and pump room hatches when the metal hatch covers are removed.  Further, a web of wooden battens is secured to the deck within the working circle of the machine guns.  Within the vessel, wood decking os provided in the magazine.

Wood grating is used in the washroom, in the heads, and in the refrigerator.

Tile is provided on deck in the galley and the heads.

Linoleum deck covering is provided in the living spaces and in the torpedo rooms. 

Linoleum over wood decking is provided in the sound and radio rooms.  Rubber link matting is provided in the maneuvering room, engine rooms and control room

Warts of weld metal provide a non-skid surface on the metal portions of the superstructure decking, and in the vicinity of the torpedo tubes.

Diamond plates are used only in the engine room.