cost to the lessees. Premium apartment for 4, 4A and 5 rooms/loft unit – Internal square metres (90–96 m², 101–103 m² and 110–114 m² / 111–120 m²) Solid timber doors for all bedrooms Semi-solid timber doors for bathrooms Polished homogeneous/porcelain tiles & timber-strip for Living/Dining & Bedrooms Standard apartment for 2, 3, 4 and 5 rooms - Internal square metres (40–55 m², 65 m², 90–94 m² and 110–120 m²) Semi-solid timber doors for all rooms (OCS) Glazed ceramic tiles for Living/Dining & Bedrooms (OCS) Optional Component Scheme (OCS) – More flexibility and choices to have floor finishes and internal timber doors installed. The opt-in basic cost are usually about 20~30% cheaper due to bulk purchases and less labour charges. But those who want variety of timber or bi-fold doors design, and better homogeneous/porcelain tiles or tiles/timber skirting can opt out of the schemes. Universal Design (UD) – These include ramps at main entrance, levelled floors throughout the flat, wider internal corridors, bedroom and toilet doors, wheelchair-accessible common toilet, space provision for future installation of grab bars in all toilets, as well as easily accessible switch sockets, TV outlets and telephone outlets. New HDB Flats such as Fernvale Vista launched from July 2006. Ferrolite Wall – HDB new patented wall using a material called ferrocement, which is similar to concrete but uses less sand as it contains a steel wire mesh. A ferrolite wall uses 20 per cent less sand than a concrete one. It is less susceptible to cracking and heat from the sun and has better sound-insulation capabilities. It is a piloted project launched from 2006 for selective Fernvale Court, Treelodge and Kim Tian Green. BTO projects The demand for BTO flats was low in the first years, resulting in the cancellation of 5 projects as it did not meet the requirement of minimum 70% application ratio. However, once the demand recovered, HDB has launched between 20 and 40 BTO projects annually since 2010, which consists of 15,000–28,000 units. By the end of 2015, HDB had launched 251 BTO projects, comprising 168,453 units. Construction costs for 5-room, 4-room, 3-room & 2-room units respectively averaged about $160,000, $120,000, $80,000 & $40,000 (based on 2004 cost). This also include the cost of sub-contractors and construction of multistorey car parks, lifts, electrical substations (ESS), child-care centres, playgrounds, fitness corners, linkway shelters and general landscaping. References External links Buying Process (New Flats) Public