Hire an interior designer when your project involves architectural drawings, custom materials, structural changes, or whole-home scope. The clearer test: if your project requires permits, a designer or design-build firm should be involved. If you are decorating a finished room with off-the-shelf furniture and standard paint, you probably do not need a designer. The middle ground (a single-room remodel with
custom touches, a kitchen update with semi-custom cabinetry) is where the value of hiring a designer is highest because the project is small enough to benefit from focused expertise and large enough that mistakes are expensive.