How Can I Measure The Sill Height Of An External Door?

The process of installing a new exterior door involves leveling and weatherproofing the bottom of the opening, as water is most likely to enter and damage flooring, subflooring, and framing. To determine the door dimensions, start by measuring the width and height of your existing door. Consider the characteristics of your sill, such as the swing of the door (inswing or outswing) and the material of the sill cap (wood or metal).

When replacing a door, it is important to measure the existing rough opening, which is the structurally-framed opening in the wall that receives the door. Accurate measurements for a door threshold require more detail than just the length of the opening, as improper measurements can cause problems with the door’s fit later on.

For exterior doors, measure from the bottom of the threshold to the top edge of the horizontal door jamb. This should be done on both sides, inside and outside, of the door. Improper or nonexistent sill pans can allow air and water to get underneath the doorsill and into the subfloor, leading to damage of hardwood floors and mold.

The measurements for an exterior unit include a head jamb, door, and sill. Most doors have roughly 1 1/4″ of height from the bottom of the door frame to the door bottom (as it swings open). The height of the sill itself depends on the manufacturer, usually 1 1/4″ to 1 1/2″ measuring the inside square edge. Hinge patio doors can come as a standard size.

To determine the nominal door size needed, measure the width and height of the existing door slab and round each number up to the nearest inch. The exception permits a 7 3/4-inch threshold at exterior doors for dwelling or sleeping units not required to be Accessible, Type A or Type B units.