Doors and Windows - How to cut out rot on door frame

Hellow,

My outside back door frame has rot down at the botton for about 3 inches. The frame sits against a concrete side and floor. What tool can I use to best cut a clean horozontal cut on the frame to cut out rot and replace with new wood? Thanks

A reciprocating saw. You can also start the cut with a hand saw (to make the location of the cut precise) then continue with the sawzall. Depending on the door, it's often better to just remove the face trim and replace it rather than piece it in. If you are saying the jambs are rotton at the bottom, then the door's pretty far gone.

I would probably replace the jambs, but if I were going to just cut out the rotted wood and piece in a replacement I would probably temporarily remove the door and trim and use a circular saw. Pull the door stops and use a speed square as a fence to get a straight cut on the jamb. If you decide to do it this way undercut the jamb a bit and cut a matching miter in the new piece to get a better looking joint.

If it is the jamb, jambs are difficult to replace in a modern door frame. The jambs and threshold are nail/stapled together. If it is the brickmold, as suggested above, remove the whole thing and replace it with vinyl or composite molding.

Thank you for the posts.

It is the jam that is rotted in addition to the bottom of the brick moulding. In fact, dry rot has gone thru jam at bottom and when I was cleaning out bad wood the staples are exposed. I could just pull them out. Incidently, dry rot caused by a gutter overflow in corner of house I never see. It is now fixed.

Using a sawzall, I plan to cut jam at high enough place where I have good wood all the way across (about 1 inch below bottom hinge). Can I just piece in a new jam piece? This door is an outside metal door at the back of my garage and has concrete steps on outside and concrete pony walls on each side. House and Door was constructed in 1994. The jam has a grove cut into it where weather stripping is inserted. Is this type of jam a standard?

Thanks again for all the help

David