(a) In this subchapter:
(1) “Building” includes an establishment or multifamily dwelling.
(2) “Substantial improvement” means:
(A) the repair, restoration, reconstruction, improvement, or remodeling of a building for which the cost exceeds 50 percent of the building’s value according to the certified tax appraisal roll for the county for the year preceding the year in which the work was begun; or
(B) a change in occupancy classification involving a change in the purpose or level of activity in a building, including the renovation of a warehouse into a loft apartment.
(b) For purposes of this subchapter, substantial improvement begins on the date that the repair, restoration, reconstruction, improvement, or remodeling or the change in occupancy classification begins or on the date materials are first delivered for that purpose.

(c) For purposes of this subchapter, construction begins on the date that ground is broken for a building, or if no ground is broken, on the date that:
(1) the first materials are added to the original property;
(2) foundation pilings are installed on the original property; or
(3) a manufactured building or relocated structure is placed on a foundation on the original property.