Ohio Rev. Code Ann. § 1521.01
As used in this chapter:
(F) "Well" means any excavation, regardless of design or method of construction, created for any of the following purposes:
(W) "Substantial improvement" means any reconstruction, rehabilitation, addition, or other improvement of a structure, the cost of which equals or exceeds fifty per cent of the market value of the structure before the start of construction of the improvement. "Substantial improvement" includes repairs to structures that have incurred substantial damage regardless of the actual repair work performed. "Substantial improvement" does not include either of the following: