How To Raise The Inside Floor By Modifying The Outer Aluminum Threshold?

In this video, Ask This Old House carpenter Nathan Gilbert demonstrates how to replace an adjustable door threshold sill for an exterior inswing door in just minutes. The process involves measuring all dimensions of the old threshold, including length, width, and thickness, and using these measurements to purchase material for the new threshold. The installation process takes between two and three hours, and it is important to protect floors with a drop cloth before beginning.

When replacing an exterior door, it is crucial to make a threshold out of wood that steps up from the floor slightly to the desired height. If needed, shims can be used to level the threshold. The aluminum gets supported by a kick applied to the outside, with the casing butting to the kick. A lower door threshold seal unit can be acquired that slides onto the bottom of the door and is adjustable by sliding up and down.

Another solution is to use a threshold that rises a maximum of 1/4 inch on the inside and drops 3/4 inch at a slope of 1:2 at the exterior. If the exterior threshold doesn’t require screws, use an appropriate adhesive (like construction adhesive) to fix it onto the floor. Finish with lining caulk.

To create a recess for the threshold, remove the wall’s bottom plate(s) and possibly the plywood sub-flooring below the door. Drill a few series of holes along the short end of the threshold, forming crude slits, and then pry with a crowbar towards the gap caused by a new floor in an older home.