One wall of our stand alone garage is effectively a fence/ wall for our neighbors. The shared fence stops at the garage and the garage wall is used to separate the property for the remaining property line.

The neighbors use the land next to our garage as a vegetable garden and water it regularly.

The wall is rotted, and water often seeps into our garage floor.

We would like to rebuild the wall and allow for their gardening but protect our garage.

Any suggestions on how to do this?

Would Flashing work?

We are in California and was told by one builder that we could not build a partial 3' cement wall... any other suggestions?