A wall fix has gone into OCMOD3. Previously walls cost nothing to build but they did cost the resource to upkeep. I understand this problem is in the vanilla game and has been in C3 for a long time. Now, walls cost resource to build in OCMOD3 and then cost upkeep in that resource as well. The up front wall cost in OCMOD3 is 100 stone per stone wall section and 40 wood per wood wall section. This fix comes courtesy of Wralth, the creator of "Cossacks Annihilation" mod. My thanks to Wralth for permission to use this fix in OCMOD3. What a great modding community C3 has! People share ideas and code freely and helpfully. This is the right way to get the best mods done to suit various playing tastes.