3-Room HDB Interior Design Singapore 2026: Layouts, Costs & Space-Saving Ideas A 3-room HDB interior design and renovation in Singapore costs $30,000–$50,000 for a BTO flat and $38,000–$62,000 for a resale flat in 2026. At 65–68 sqm, the flats that feel biggest share three things: one continuous living-dining zone, full-height built-in storage on a single wall per room, and a palette of no more than two material families. Carpentry, not decoration, does most of the work. De