What Is the Difference Between a Door Threshold and a Door Sill?

When building and installing your own door or maybe just installing a store-bought door, it is important to know the difference between the door threshold and the door sill. There are those that believe that the two are the same and possibly use the terms interchangeably. There are even certain dictionaries that define the terms interchangeably. However where it has been convenient to make a distinction, most standard definitions separate the two terms as follows.

Door Sill

On a door frame, the sill is the portion of the door frame that runs along the bottom and sits directly on the foundation of your floor. It is the cross piece that actually completes the pre installed door frame. The sill is actually underneath your threshold.

Door Threshold

The threshold of your door can be made of either wood or metal and it is the sloped cross piece that extends across the bottom of your door area. It is slightly raised to keep water from flowing in and often is fitted with a piece of weather stripping to help insulate the area underneath your door. The threshold sits on top of the sill.