Centre (Brahmasthan)

It's a major Vastu defect — among the worst in modern apartment construction. You can't structurally remove it. Mitigations: hang a Vastu Yantra (copper) on the underside of the staircase; install bright lighting around the staircase area; never use the under-staircase space as a toilet (worst), kitchen (very bad), or storage (bad) — leave it open or use as a small puja shelf; perform a Vastu Shanti Puja annually. Plan a future move to a structurally-correct home if family stability concerns persist.

Classical Vastu divides any plot into a 9×9 grid (81 squares). The central 3×3 (9 squares = approximately 1/9 of the total area) is the Brahmasthan. For a 1000 sq ft apartment, that's ~110 sq ft in the centre. For a 3000 sq ft house, ~330 sq ft. The exact boundary matters less than the principle: keep the geometric centre open, light, and unburdened by walls / heavy elements / fire-water installations.

Yes — Tulsi is one of the few plants that BELONGS in the Brahmasthan. Tulsi's sattvic energy aligns perfectly with Brahma's seat. Place it in a clean elevated terracotta or brass pot, ideally in a small atrium or courtyard area. Water and care for it daily. The Tulsi plant in the Brahmasthan is one of the most powerful Vastu activators available — almost no other plant has the same effect.