Undercut and Prep a Door Casing
Floor prep for most residential installations includes undercutting the door jamb and casing where the flooring is going to tuck underneath it. Most often, I’m going to use a piece of the flooring material that I’m going to be installing to match the height. My goal is to cut so that the flooring tucks underneath. This can be done with a flush cutting pole-saw, an oscillating multi-tool, or an undercut jamb-saw. The undercut jamb-saw is quicker and more aggressive, but can make more of a mess. I like to use the oscillating multi-tool.
To start, I slide the board tight to the part of the door jamb and casing that I’m going to cut and score it cleanly to avoid splintering. Then I come back and plunge through. What does not work well is to try to plunge all the way through one area, and then shift and plunge all the way through another area. You end up with a really jagged cut that way. Working the entire jamb or casing ensures a clean cut.
If the flooring is not continuing through into the other room, the cut is going to stop typically right in the middle of where the door swings. So, when I precut these at the beginning of a job, I’m only going to cut up to a certain point and leave the other part uncut because I may not have a transition strip (such as a reducer) that tucks underneath the way that the flooring does. I might have to cut my transition strip just to butt into the door-jamb instead of tucking under it.
Lastly, I will go through and confirm that my flooring slides in and out of the frame easily without a bunch of effort because I don’t want to have to fight it in, and you don’t want the door-jamb to impede on any movement the flooring needs. Sometimes that cut might slightly angle as you go. If it does, I’m just going to slide it in to where it pinches and run the oscillating tool over it again to trim it that last little bit. Now, when I come back to install the floor, if I want to adjust it, I can do it easily, but it’s prepped. It slides in there nice and tight without a major gap and it is going to look really clean when it’s done.
For additional information about installation around door jambs and casings, check out the NWFA’s Installation Guidelines at nwfa.org/technical-guidelines/.
Watch it!
See Ben Totta complete this process.