A home design trend that starts in the kitchen, bedroom, or living room can move into the bathroom over time. Case in point: wood treatments on the ceiling. Be careful here. Moisture and wood are a bad combination. The heat and steam from a bath or shower could warp and split the wood as it rises, or worse, encourage mold growth. Once mold takes hold on wood boards, it's hard to budge. If you want your ceilings to last for many maintenance-free years, you may want to consider a traditional ceiling painted in a coat of paint rated for high-moisture environments.