Choose Height and Panel Style Before Cutting
Wainscoting changes the proportions of a room, so the height should relate to the wall, windows, doors and surrounding trim. The best location is not necessarily the same in every house.
Panel style matters too. Raised-panel, flat-panel, beadboard and applied-molding systems create different joint and layout requirements. Before installation, the design should be carried around corners and openings so narrow leftover panels do not appear accidentally at the end of a wall.
Lay Out Panels Across Doors and Corners
A good panel layout is planned from the whole wall rather than built one panel at a time. Door openings, windows, outlets and inside corners can interrupt the pattern, and those interruptions should be resolved before rails or stiles are fixed in place.
Walls may also be out of square or slightly uneven. Trim components sometimes need to be fitted to those conditions so the finished grid appears consistent even when the underlying room is not perfectly regular.
Repair Existing Wainscoting or Install New?
Localized damage can often be repaired when the surrounding rails, stiles and panels are secure and the profile can be matched. A missing panel or split piece does not always require replacing the entire room.
If several sections are loose, the wall behind the system is damaged or the old material cannot be matched, a larger replacement may produce a cleaner result. Drywall repair and final painting are separate considerations; wainscoting installation should not be used to cover an unresolved wall problem.