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Finding door cut off for new threshold

5645 Views 10 Replies 8 Participants Last post by  grizzman
HI all,

I have to install a new threshold and the door will need to be cut off. I thought I would use a wedge pushed under the door when it is nearly closed to find it's existing height; then, level from the elevation of the new threshold to the same floor surface. The difference between those 2 measurements will be the cutoff to make the door fit.

Do any of you experienced door hangers have a better way to find the cutoff?


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I would completely remove the old threshold leaving the door hanging normally. Then I would put the end of the new threshold on the floor and against the door on the hinge side and mark is with an awl. Then I would repeat that procedure on the lock side of the door making certain that sufficient pressure is applied to the threshold gasket so the door will seal tightly. Then you can use those two marks to make a straight cut line for your cutoff.

Another couple of points is to use a clamped straight edge for the cut and make sure you score the cut line to avoid tear out if any part of the cut is across the grain. Even a fine blade will tear out on veneer.

Unless your straight edge has a surface for the saw to ride on, tape the entire surface to avoid scratches. The metal bases on circular saws are notorious for scratch delicate surfaces.

A couple more thoughts; if the door swings out you can make the cut at a small angle for a tighter fit. It's usually not a great idea for doors that swing in. And, you can also purchase a slide on weatherstrip for the bottom of the door. I did that when I installed a new front door on my home and it works great.
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Thanks Bill, The old threshold was site built, soft wood and was worn quite a bit. The old threshold was removed long ago. My door swings in. The floor is higher than the rough level of the new threshold. That is my problem getting a good measurement for cutting off the door. I bought a new metal one with a weatherstripping built in.
Top, remove the old door and threshold and install the new threshold making sure it is level. Measureing up from the threshold to the bottom of the hinge on the door jam will give you a good measurement. Then measure down from the door hinge the same distance, minus what ever gap you need for weather stripping. As Bill said be sure you score your cut to prevent tear out. A good straight edge and a razor knife will do fine. Have fun.
One other hint.
Make sure all of your hinge screws are tight before measuring.

Also check for worn out hinges.
Bob - I don't know how much this will help, but with the right tools, the difference in floor level can be measured. I did it here in my old 140 year old house in several rooms and had great luck. I even used this method for a landscaping project.

Tools needed are one of the new digital leveling systems with a light beam. You also need a drill press with a depth stop.

I found a good flat piece of hardwood (plywood, MDF or hardboard will do fine) and drilled identical holes using the depth stop on my drill press. I then cut up a couple of dowels and put marks on them at equal lengths from the bottom, stuck them into my blocks (pre-drilled holes were the dowel size). To test my system, I placed them on my level workbench and set up my laser level. When I got the line dead center with the lazer beam, I knew I had my measuring stick. To test it, I shuffled the blocks and found them to still be on the mark.

I placed one block on the low point of the floor and set up the level so the beam was on my mark. I then moved the other blocks around and measured the distance between the marks on the dowels and the beam. I now know how much my floors have sagged in the past 140 years.
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They make adjustable metal thresholds with a rubber seal. You removed the seal and adjust the threshold with screws and replace the seal to hide the screws. The door seals on the rubber seal. This makes it possible to adjust one end higher if needed to help with imperfections like a house that has shifted in the wind. I like to cut the door at a 5 degree angle so the short side (outside) can slide up over the rubber seal without damaging it yet the door will push down on the seal when closed. ???
Thanks guys, I am fortunate the floor is level and flat. The sub-floor is 2" t&G. I will definitely score before I cut. The 5 degree sounds like a good idea to make a good weather tight seal.
1. Measure down from the head jamb with the old door in place.

2. Install and level the new jamb.

3. Measure down from the head jamb.

4. Subtract the difference, add 1/8" (or whatever you choose) for the floor sweep gap, and cut the bottom of the door.

Thanks, Never thought of measuring from the top. Probably would have pre-Topamax ;-((
hire a carpenter and then watch some football and eat snacks while he hangs the new door…....LOL…..
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