If you have a bathroom closet with movable shelves, you can place them at virtually any spacing that works for you. Useful measurements between shelves in the working, or middle, section can be 10 to 16 inches for towels or linens. Lower or higher shelving could be up to 24 inches between shelves to store lesser-used or bulky items or boxes. 

To prevent sagging, consider both the material and the span of the shelf. Using sturdy materials such as plywood or solid wood can provide better support than particleboard. Additionally, limiting the shelf span to 36 inches or less can reduce the risk of sagging. For longer shelves, incorporating center supports or brackets can offer additional reinforcement.

Yes, adding a built-in or custom closet generally increases your home's value and makes it more attractive to potential buyers. A well-designed closet adds utility, organization, and a touch of luxury, which are appealing selling points. Most homeowners see a return on investment (ROI) of 50% to 60%; for example, a custom closet can add about $1,000 to your home's value on average. The specific ROI depends on the type, with custom walk-in closets typically providing more value than reach-in closets. However, to maximize value, ensure the closet doesn't significantly detract from the room's usable square footage. Converting an entire room into a closet can actually lower your home's value. Similarly, using overly lavish materials may not recoup their cost. A good strategy is to add a closet that takes square footage from a non-living area, such as a garage, to create a mudroom closet.

Closet design services include help designing and laying out your closet for maximum utility, visual appeal, and return on investment. Many closet designers can also include the carpentry required to construct your custom closet. You should speak with your designer beforehand to determine what services are included in the estimate, and prepare to lay out additional funds for materials or labor as needed.