Indigenous to Southern Asia, teak is a tropical hardwood wood known to have excellent resilience to moisture. Teak is commonly used in marine applications and it's natural resistance to rot and decay makes it an excellent material for moist environments. Although the lumber is costly, building your own teak shower bench is typically more cost effective than buying one.
Lay two 16-inch boards on edge, parallel and 9 inches apart. Place the 9-inch boards between them so they are perpendicular to the 16-inch teak boards, and 14 inches apart. Screw through the 16-inch boards and into the ends of the 9-inch teak boards. This is the frame to your teak shower bench.
Lay the frame flat and position the 15-inch teak boards perpendicular to the inside corners of the frame. Screw through the corners of the frame using four screws for each corner to secure the 15-inch boards. These boards are the legs to your the bench. The legs must be even to ensure your bench doesn't wobble, so be sure the ends of the 15-inch boards are all flush with one side of the frame before they are screwed.
Position the bench upright and screw the 11-inch boards to the top of the frame. They should be parallel with the 11-inch sides of the frame. The ends should be flush with the 16-inch side of the frame. The two outside boards should be flush with the 11-inch sides of the frame.
Sand down the bench with medium and then fine grade sandpaper to prevent splinters. Wipe the bench with a damp cloth before use.