Heavy duty I recommend these types of shelves to my clients all the time because they hold a lot of weight. Great for garage, basement, attic, laundry room etc. Assembly required so they are easy to squeeze into any space before putting together.
Easier to build than fixed shelves -- Adjustable shelves make space more versatile, and they're usually just slabs of plywood nosed with strips of wood or edge banding, so they're easy to make. And because you can remove them, adjustable shelves simplify staining and finishing. The easiest way to support adjustable shelves is by using shelf standards are ($3 for 6 ft. at home centers). Just screw them into place and you're done.