Remodeling projects often require trimming the bottom of an interior door. Installation of new floor covering often raises the height of the floor, causing the door bottom to bind against it and preventing proper operation. To solve the problem, remove the door from its hinges and cut the bottom shorter–but keep in mind, there’s a right way and wrong way to do this.
How Much Clearance Floor is Required?
For basic function of the door to swing open and closed, its bottom should clear all obstructions (floor registers, etc.) by at least 1/8 inch. Now, depending on the circumstances of the room in question, you might want more clearance to allow better return airflow throughout the house.
For example, we recently trimmed the door of a kitchen pantry which had no air-conditioning duct, so we kept the floor clearance to 1/8 inch because the homeowner preferred the look of a smaller gap, and the door had no issue with airflow. However, a bedroom with HVAC registers is usually separated from the air return by the door, in which case a very tight gap beneath the door may restrict the system’s airflow. A common symptom of this is a door that resists opening or that slams shut when the HVAC system activates, due to an air-pressure imbalance. In this case, a 5/8-in. gap beneath the bedroom door is considered standard. For floors with high-pile carpets, a larger gap might be necessary, and for venting the humid air of bathrooms, some pro remodelers recommend as much as 7/8-in. door-to-floor clearance.
How to Shorten a Door
Side Note 1: Make a Saw Guide
If you don’t have a saw guide like the one shown in the photos, you can custom-make one to fit your saw, as I demonstrated at Extreme How-To several years ago.
Side Note 2: Matt’s Video on How to Shorten a Door
I made this video for ‘Extreme How-To’ a few years ago. Enjoy!