Need help with door trim in an old house


Old 03-20-17, 12:54 PM
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Need help with door trim in an old house

I installed a new pre-hung door in a bathroom with a rough opening which was front-to-back about 1/2" deeper than the door jambs.I aligned the jambs with the outside, so on the inside I have a bit of a mismatch between the jamb and the interior plaster wall. I'm wondering if the best (easiest) way to build the inside trim is just to put my seldom-used dado blade on the table saw and remove the excess from the three trim pieces. The trim is 1x3", so I would be removing about 1/4" of wood for about 3/4" back from the outside edge of the trim so that it sits nicely on the interior wall. Does that make sense?

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Old 03-20-17, 01:39 PM
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Which way does the door open? The hinge side should be flush with the wall [assuming it's plumb] You'd then build out the other side of the jamb so it will be flush with the wall prior to installing the casing. I often rip a 2x to the correct thickness.
Old 03-20-17, 02:45 PM
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Door Jamb

Rip door jamb material to the correct width to make the jamb extension flush with the surface of the drywall. Drill pocket holes on the back side of the extension. Attach the jamb extension to the existing jamb from the back side with pocket screws. Install the facing trim.
Old 03-20-17, 02:59 PM
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In addition to what wirepuller said about the jamb and pocket screws... you can buy jambs in single pieces that will match your existing jambs.... and then rip them to the right width on a table saw. You can then drill pocket screw holes in each piece and assemble the extension jamb.

But when you measure the length of your extension jamb pieces, you don't want it to line up exactly with the other jamb... you actually want to make the top piece about 1/4" longer and the side pieces 1/8" taller so that you have a small 1/8" step (also called "reveal") where the extension jamb meets the door jamb.

And I agree completely with what marksr mentioned, that you want to install the extension jamb on the side of the door that does NOT have the hinges or strike plate. The hinge side of the door should be flush with the wall on that side of the door.
Old 03-22-17, 08:05 AM
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Thanks for the what-I-should-have-dones. Next time will be a lot easier.

The door is already installed, and I don't want to redo that from scratch. I have a bunch of 1x4 pine boards, and I'm making some mockups before I start cutting into the poplar I bought.

Thanks again
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