Stone walls.

[dy2000]

2 bugs/technicalities in this one...

1.) I plowed a field next to my stone wall and somehow it did damage to my stone wall.

2.) It takes 1 granite to fix 2 percent of my wall, so 50 granite in total, but it only took 3 rock and 1 granite to build it in the first place.

[Nsuidara]

500 brick for repair brick wall..

when build need 15

[Kandarim]

most likely your wall took decay damage because it is on unclaimed soil. I am unaware of field tilling causing damage.

The repair cost for walls is all over the bugs forum, and it's fully intended the way it is - in order to balance active/passive defence and attacking.

[MagicManICT]

It was decay damage. The server sends updates to structures such as damage when you change the terrain, so if there was damage but it didn't get updated yet, you'll get the update then. (The way updates are pushed to the client are odd in some areas of the game.)

The amount of materials needed to repair walls is completely intentional. The low number of materials to build is a sort of boon to players trying to build. However, in a siege, it makes for excessively easy repairs to those walls while someone is trying to break them, so it go changed to some very ridiculous numbers. I'm sure there's a better mechanic that could be implemented if someone suggests something sensible.