Building Degradation

Condition Formula

Condition = 0.67 / (1 + e^((1789/25000) * (DaysSinceLastRepair - C))) + 0.33

C is either 100.87 or 107.87.

There is speculation that the additional 7 days for C is a bug as it happens inconsistently.

Repair cost is determined by:

RepairCost = BuildingCost - ReclaimableCost

ReclaimableCost is determined by:

ReclaimableCost = Floor(BuildingCost * ((180 - Min(DaysSinceLastRepair, 180)) / 180))

All of the above is applied on a per material basis.
If your building is affected by the 7day bug, subtract 7 from DaysSinceLastRepair. If DaysSinceLastRepair goes negative, set it to 0.

For a great walkthrough of building degradation mechanics, see this Google Sheet: https://docs.google.com/spreadsheets/d/1ELsfw4ii1hQFWDd-BL4JzwqHc-wGVXbJtvAeprv0pZ0 by MoonSugarTravels