How can I fix door jamb?

need to find out where the water damage is coming from in order to keep it from continuing to rot the wood -- this may be the tip of the ice berg -- I'd check with a carpenter/building contractor before you start ripping out stuff...

Hi, Is it solid or spongy? Solid then rub down and if dried out refinish. If spongy let it dry out or cut it out and replace the timber with new or rake out soft or rotton areas and fill with wood filler. prime, undercoat and topcoat with a good gloss paint.

It looks like that portion needs to be replaced. Replacement door frames can be found at the big box stores and lumber yards. If you want to replace the damaged sections, some second hands stores or rehabs will have similar pieces. Good luck on the repair.

Hi Shelley! I would definitely remove the damaged wood and replace it. But, you'll also want to do some investigating. Does water sit outside against the wall after it rains? Is there a gutter that needs the runoff to be redirected (a problem I had)? Is the outside also damaged? Sometimes the area is soaked whenever it rains, and it seeps in, causing the problems pictured. Sometimes caulking, flashing, etc. needs replacing. Opening it up will give you more clues. If you are handy, and have tools, it is a project a proficient amateur can do. Recently, I asked a lot of questions when insurance paid for damage repairs by a licensed contractor. A certified reconstruction contractor, he told me he always learns a lot once he opens up a wall, because he can make educated guesses, but, until he sees what is underneath, they are just guesses. We discussed what he found, as he took the wall apart, layer by layer. I had a mental picture myself, but, learned so much more as the outer parts were removed. I posted the repairs if you want to look (just click on my name and it will take you to my page). Here's a video to help you understand the process:

https://www.youtube.com/watch?v=GnHya_2HPGo

I agree with Landsharkinnc. Best to remove the trim boards and also the floor molding at least a foot away from the (Sliding??) door. It is possible the wood is rotted and I am sure there is a mold problem also. If there is mold, be sure to replace the drywall also. Mold loves drywall on the untreated/unpainted side.

If you don't want to use a carpenter a good referral for a handyman will do. The molding that is on there now doesn't appear to be the original, making me think this has happened before.

If the wood is rotted you will have to dig it out. But first and foremost you need to find out where the water is coming from and take care of that problem. If you can let the wood dry out, you can use bondo or wood fill, and sculpt it to the door jam. But it looks like you will need to replace it. It also looks like the base board is affected.