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Retrofitting an existing door into a new frame unit

Hi all! Before I post my question, I just wanted to say that I have received great advice through this blog, and thank everyone who has responded!

A friend recently purchased a beautiful fiberglass entry door with leaded sidelights, but discovered that he could not fit the entire unit into the rough opening on his home. He did, however, use the door itself, and offered the frame w/sidelights to me. My current entry door, a solid 1 3/4" thick old-growth pine, is exactly the same size as the fiberglass door removed from the frame; except for the fact that it is about 1/4" thicker. Assuming I can fit the entire unit into my rough opening (and initial measurements indicate I can), what is the best way to accomplish this retrofit? My thinking is to begin by filling the existing hinge mortises and lock locations in the frame with wood inserts and start hanging the door anew. Any suggestions would be appreciated!!

Re: Retrofitting an existing door into a new frame unit

Needless to say......we can't see all the particulars of the situation, but......
it sounds like you're on the right track.

I take it the new jamb is not installed and you can lay it out or stand it up....... on the shop/garage floor or similar to work on it.

Since your old door is 1/4" thicker than the door that came installed in this jamb .......you will have to make provision/alterations for that. In that this is an exterior door unit, the stopping for the door is likely integral to the jamb wood itself rather than an applied stopping. If perchance it is the latter.... then you would simply remove it and reapply to the needed deeper depth. However, if it's a rabbet milled into the jamb wood....you will need to remove some of that wood to make room for the thicker door.

I would likely go about this with a router and a 1/2" mortising bit that has a guide-bearing of the same outside diameter as the bit and is mounted on the shank above the bit. You can then clamp or temp-tack a straight-edge 1/4" back from the existing shoulder of the stop and run the router bit bearing against this straight-edge to remove the wood. ( A dead straight piece of lumber or strip of plywood will do fine if you don't have a dedicated straight-edge designed for these types of jobs)

Of course, this will only get you so close to the inside corners of the jamb and then the game is over with the router. (How close depends upon the size (outside diameter) of your router's
base plate) The remainder could be removed with hand tools such as very sharp chisels, etc. Don't try to blast it out with heavy blows in an aggressive manner. Rather....draw a guide-line with your straight-edge and approach the removal by taking off 1/16" depths of material at a time. Chisel down a bit and then come in from the side to remove that. Repeat until you hit
the required depth. (Pretty much the same way that you'd use a chisel to create a hinge mortise) The final cuts/slices that remove the very last of the wood must be made carefully so
that you end up with a nice clean surface. Usually these are done without the aid of a hammer of mallet, but rather the chisel is pushed with your hand. A really sharp chisel is a must.

Same may hold true for the removal of the wood with the router bit; you may want/need to remove it in a couple of passes. Depends upon the size of your router, etc.

If you don't have a router, this could hypothetically be done with a circualr saw also. Same basic principles apply. Secure a straight-edge so that the blade of your saw is appropriately
located where the cut needs to be made when the saw's sole edge is against the straight-edge. Set the saw's blade cutting depth to what is required. This approach will require that you make a plunging cut with the saw to enter the wood while still holding the saw's sole against the straight-edge. This can be be a little tricky so I'll recommend that you practice on some
scrap before proceeding if you aren't accomplished/practiced at making plunge cuts.

Re: Retrofitting an existing door into a new frame unit

goldhiller's advice is good... but before you start routing or cutting on the jamb check the thickness of your wall or at least you existing jamb. It may be easier to remove the outside trim and add a ¼" jamb extension if the wall is thicker than current construction.

Re: Retrofitting an existing door into a new frame unit

"Goldhiller", thanks for the great advice. You are correct, the new jamb unit is not installed, so I can work on it while detached. "JLMcDaniel" is also correct, and I should have specified this before. My home is a cape-style, constructed just after WWII, when a "2x4" was really 2"x4." The builders also felt the need to use 2 sheets of 3/8" sheetrock" (I call it sheetrock, but it feels more like concrete-board) with 1/8" plaster on top, perhaps to avert a nuclear attack. In any case, my walls are significantly thicker than new construction. If, in fact, the stops are rabbited in place, I will have to add a 1/4" jamb extension on the inside of the frame, and about a 1 1/2" extension to the outside. Thanks again for the advise, I'm sure I will be asking for more on this project!

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