Cutting tapered strips to fill gaps between door & frame

As part of a project to upgrade some old Victorian doors to 20min fire doors (agreement with building control), I need to decrease the gap between door and frame on several of them and them use Intumescent coating on the internal side & edges of the doors. Then finally fit intumescent strips (fire only, not smoke).

The gaps aren't uniform in most cases therefore would require tapered strip wood either on the frame or door to achieve 3mm +/- 1mm. As an example the gaps between the door and frame on one door are 10mm and taper off to 2mm on the vertical (lock) side.

What is the best way to cut tapered strips to do this? I have a table saw but it would probably be a bit rough to cut strips that thin on one end.

Alternatively would it be better to plane the door to achieve a uniform gap top to bottom and then fit uniform lengths of strip wood?

Replace the frames?

foxhole said:

Replace the frames?

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Huge amount of work to remove, re-plaster the inevitable loose bits around the frame, refit and redecorate. They are the original Victorian deep frames & architrave.

Add to 9-12mm to door liner and re-trim door to fit.

I think the best way to tackle this is to plant on more than you need then hand plane it back. You'll probably need to start by trimming the edge of the door square to the face and straight using either a portable saw or a jack plane before planting on your fillet. Note that I am talking about a hand plane, not a power planer. Power planers lack the fine control you need to undertake this task with a sufficient degree of accuracy IMHO, especially if the jambs of the casing are pin cushioned or barrelled

If the doors have locks fitted I'd probably plant on on the hinge edge and recut the hinge recesses afterwards because this is less work than trying to adjust the position of a lock. Less noticeable, too, although longer than supplied (with the hinges) screws are highly advisable