Repair trim around garage doors

The bottoms of my garage door trims are disintegrating a bit. What would be best to repair this before repainting? Could Bondo work?

Thanks

 

It will work for a while. You should probably slide a wide putty knife under... then pull it out once you have shaped it. You don't want water wicking up into the trim. That gap will get caulked.

 

That's not wood. It looks like a masonite or similar product. It is difficult to get many things to bond to it. I have had luck by mixing up some polyester fiberglass resin and thin it with alcohol. Then I brush on several coats to soak into the masonite. Then apply the Bondo (make sure it's the polyester type) while the base coating of resin is still wet. It is helpful to slide a sheet of cardboard underneath covered with wax paper. Then after the Bondo has firmed you can remove the cardboard and wax paper leaving a nice gap underneath and clean concrete.

Or, you can cut off the bottom of your trim and install new material. Something rot proof like PVC would be a good choice though wood or more masonite can be used if properly painted.

 

If you want to fix it for good, remove all the trim boards and replace it with PVC. Looks like your trim next to the door is already PVC, so you may be able to salvage that.