After a building has been built, it will slowly start to decay (lose hit points). To prevent decay, the building must be connected to (within its AI range) a base with Garrison Facility upgrade and stockpiled with Garrison Supplies (bunker structures can alternatively use Bunker Supplies) . You can check the hp% of a structure with your hammer equipped and standing close to it.
- Decay within 100m from a border is not preventable and happens faster.
- Decay does not start immediately, the grace period lasts a few hours for fast decay and one day for normal decay.
- Repairing a decayed structure partially restart the grace period, proportionally to how much health you repaired.