A splayed window jamb is one that angles outward or inward rather than being perpendicular to the wall and allows more natural light to enter the room. It may also provide a broader field of view from inside the building.

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Splayed window jambs are commonly found in traditional masonry construction, where the thick depth of stone or brick walls offers space for such design flourishes. The inward splay—wider toward the interior—acts almost like a light funnel, increasing illumination and enhancing the perception of openness in otherwise deep-set windows.

This detail often had both practical and aesthetic purposes in historical buildings: improving light distribution while adding architectural character. While less common in modern wood-framed construction due to thinner wall profiles, splayed jambs may still be used for stylistic effect, particularly in custom or restoration work. They should not be confused with window returns or casing; a splayed jamb refers to the angled portion of the window recess.