Rotting front pillars on 10 year old home. HELP

I am a handyman with not a lot of experience and i have a client with pillars on the front of their house that are rotting away. There are 4 pillars like this. I tried uploading pics but it keeps saying “The file in the field was unable to be uploaded.”
Inside the pillar you can feel a PT 4×4 that appears to be still solid. But before I rip everything off I would like to know how to put it back together in a way so this won’t happen again. And this is happening to the entire neighborhood so theres a good chance ill be hired to fix a lot of them.
The pillars have a 4×4, with a 12″ decorative wood design around it. It appears that there is dirt inside the empty cavity. Is that normal? I can’t figure out why they would do that. If i rip it all off and replace it, how can I make it water tight?
Any info would be super helpful. I want to do it right.
Thanks
Troyal
Replies
Mainly the wood surround needs to be held off the concrete by an aluminum base casting, or perhaps a build-up of composite plastic lumber pieces. Then there needs to be a small amount of airflow through the column so it can dry out if it gets wet inside (though either make any holes small or screen them, to keep out nesting bugs).
That makes sense. Thanks for your help!!
Easy fix and looks good as well. Cut the trim wood off all the way around at 11 1/2" above the floor. Use 1" X 12" PVC trim board to make a replacement for the bottom but make it stand proud of the pillar so it looks like a base. You'll need to pad the bottom out so the PVC will look like a base. This fix looks like it was done on purpose and the PVC won't be damaged by water.
Ill look into the PVC. The client likes that idea. Thanks!!!