How Interior Designers Charge for Their Services Designers work with a variety of fee structures, and as with other professions, base their fees on variables such as complexity of the project and its geographical location and the expertise of the designer. Most designers will work in one of the following methods, or combine methods to suit a client's particular needs: Fixed fee (or flat fee) -- The designer identifies a specific sum to cover costs, exclusive of reimbursement for expenses. One total fee applies to the complete range of services, from conceptual development through layouts, specifications and final installation. Hourly fee -- Compensation is based on actual time expended by the designer on a project or specific service. Percentage fee -- Compensation is computed as a percentage of construction/project costs. Cost plus -- A designer purchases materials, furnishings and services (e.g., carpentry, drapery workrooms, picture framing, etc.) at cost and sells to the client at the designer's cost plus a specified percentage agreed to with the client. Retail - The designer sells furnishings, furniture and all other goods to the client at retail rates to cover the designer's fee and services. This is most applicable to retail establishments offering design services. Per square foot - The designer charges fees based on the area of the project as might be calculated for large commercial properties. In addition to the fee structures outlined above, designers may require a retainer before beginning a design project. A retainer is an amount of money paid by the client to the designer and applied to the balance due at the termination of the project. The retainer is customarily paid upon signing the contractual agreement in advance of design services.