पञ्चदशहस्तादेकोत्तरमाष्टादशहस्तादिति तलोत्सेधः ॥ कZ_०२.३.१७ ॥
pañcadaśahastādekottaramāṣṭādaśahastāditi talotsedhaḥ
The plinth/ground-level elevation (talotsedha) is prescribed as: from fifteen cubits up to eighteen cubits plus one (i.e., nineteen cubits), depending on the standard adopted.
To standardize construction for safety and durability (e.g., drainage, flood protection, structural stability) and to make inspection/enforcement feasible.