How tall can a wardrobe or cabinet door be before it warps?

Tall doors over about 1.8–2.0 m can bow over time, especially wide panels in board materials. The standard solutions are a door straightener (an aluminium profile set into the back), a stiffer substrate such as plywood or a framed door, or splitting into two doors. For full-height wardrobes in villas we normally specify straighteners as standard rather than as an upgrade.