A flush door is a completely smooth door, having plywood or Medium Density Fiberboard fixed over timber frame which is comparatively light. The hollow core also obtained is often filled with a cardboard core material.
Flush doors are most commonly used in the interior of a building, although with some variations they are also used as exterior doors in houses.
The frames for such doors can be made out of wood, steel etc, which can hold its weight. The doors are usually hinged along one side to allow the door to open in one direction only.
Flush doors are commonly provided in houses these days due to the reasons of economy, pleasing appearance, durability etc and are commonly available in the market.
While providing these doors for toilets, baths; the inner face of the door should be covered with aluminum sheets or have a PVC (Polyvinyl Cholride) to provide protection against water.