Infill

Infill is a term used across disciplines to describe filling existing spaces or voids with development, material, or structure. In planning and architecture, infill development refers to the construction of new buildings on vacant or underused parcels within existing urban areas, rather than on undeveloped land.

Infill development aims to promote sustainable growth, make efficient use of infrastructure, support transit-oriented development, and revitalize neighborhoods. Benefits include increased density, revitalized neighborhoods, and improved reuse of brownfields. Challenges include zoning barriers, neighborhood opposition, infrastructure capacity, and potential displacement. Local governments use zoning amendments, design guidelines, and incentives to encourage appropriate infill.

In 3D printing, infill refers to the internal structure that supports a printed object. It is not solid; the density (often expressed as a percentage) and pattern affect strength, stiffness, weight, and print time. Typical patterns include grid, honeycomb, and gyroid. Lower infill saves material and time but reduces strength; higher infill increases durability but uses more material and prolongs printing. Printer settings and material properties influence optimal infill.

The term is also used in other contexts to describe material that fills gaps, cavities, or voids, such as infill in archaeological deposits, civil engineering, or geotechnical work, where it serves as filler or restoration.