how to fix rotted porch post
Structural porch column rot repair:
Jayne: you might want to consider replacing --- especially if it impacts the integrity of something that NEEDS support.
Otherwise... there are products suck as this:
You should replace it. Use pressure treated lumber
Where are you shopping for the posts? Can you share a photo of the posts/columns?
Repairing a rotted porch post is generally going to be a band aid that won’t last terribly long, especially if it’s ground contact. Further, if the pieces are structural, it is much better to replace them for safety reasons. I have never heard of pressure treated lumber being $300 a piece, you might shop around.
Before investing in repair, I would try to figure out what caused the rot (sitting water, rain gutter drainage, ground contact). Then, I would try to remove the cause. If it is superficial damage, it can be repaired by repairing that area. If the post itself is compromised, you may have to replace it. Unless it is a custom order column, I can't imagine a post costing that much. If all the posts need replacing, I would be concerned about the porch itself and its structural integrity. Good luck!
Here's a video that might help you - https://www.youtube.com/watch?v=s6naaDBrZSc
If you have no water lying issues and it has rotted then what has caused it! Is it dry rot? Insect infestation? Remove and replace rotted timber or maybe give it a Concrete Boot! Best wishes.
You would need to replace the post