SINGAPORE - Buyers of the 94 Build-To-Order (BTO) projects currently under construction have to wait between two and 5.9 years for their homes, with a median waiting time of around 4.3 years.

At the peak of the Covid-19 pandemic, the waiting time for a BTO flat was around four to five years, up from the pre-pandemic norm of three to four years.

The Housing Board on Saturday said BTO waiting times vary due to the location of the site and complexity of the project.

BTO projects in built-up areas, such as those near other residential blocks, facilities and infrastructure including underground MRT stations, will require more preparation works to minimise disruption and disturbance to the community.

Complex projects – those with taller blocks of 20 to 50 storeys and those with additional design features such as staggered block heights, sky terraces, basement parking and environmental decks – also take longer to build.

Likewise, projects that are integrated with developments such as a hawker centre or bus interchange will also require more time to plan, design and construct.

In the coming years, the HDB expects to launch more complex BTO projects, including in brownfield sites that previously had developments on them.

Some 5,000 BTO flats will be built on the Old Police Academy site in the Mount Pleasant area, and another 6,000 BTO flats on the Keppel Club site in the Greater Southern Waterfront.

The HDB said the process of conceptualising and building new housing projects typically takes several years across the planning, design and construction phases.

Large housing areas are drawn into the masterplan years before any developments are launched. Infrastructure such as roads and utility services, parks and community facilities are factored into the plan. For sites with environmental or heritage considerations, the HDB will conduct studies to guide its development plans.

About one to 1.5 years before a BTO project is designed, the HDB works with various agencies to finalise the requirements. The Urban Redevelopment Authority has to approve the gross plot ratio and site development boundary.

Land preparation works are carried out during the two years taken to call and award the various building tenders for the development.

Then, construction of the BTO project starts.

The HDB provided details of an ongoing complex BTO project, Kempas Residences, in the mature estate of Kallang/Whampoa.

Launched in May 2019, the project was slated to take around four years and eight months to build, but the pandemic delayed its expected completion by six months to end-2024 to early 2025.

Kempas Residences has four blocks ranging from 29 to 37 storeys, and the site is located near Boon Keng MRT station and buildings such as Kallang Polyclinic and Kwong Wai Shiu Hospital.

The Straits Times looks at how this project is being built.

Stage 1: Preparing the site for construction works – 3.5 months

To minimise noise disruption, a higher hoarding of 12m has been constructed for the site, which sits near existing HDB blocks and a hospital. Regular hoardings are 6m high.

The HDB liaises with various parties to ensure existing underground services, including electricity cables, telco cables, water pipes, gas lines and sewer lines, as well as infrastructure such as roads and train stations are not impacted during construction.

As the site sits near a busy road, HDB had to obtain conditional access for heavy vehicles from the Land Transport Authority (LTA).

Soil improvement works to strengthen poor-quality soil as well as earth works are carried out where necessary.

Stage 2: Laying the foundation of the HDB blocks – 9 months

Steel and concrete piles are drilled into the ground to serve as a sturdy base for the development. As this BTO site is near homes and a hospital, piling works have to adhere to the National Environment Agency’s (NEA) noise guidelines.

The ground slab – or foundation – of buildings is constructed. As these works are susceptible to wet weather, some time may be required to pump out water from excavated pits.

Underground sewers and a service tunnel used to house cables that will supply essential services to each flat are also constructed.

Stage 3: Building the HDB blocks and residential units – 34.5 months (overlaps with Stage 4)

Large precast components such as facade walls and pre-fabricated bathroom units are produced in precast yards.

These yards are in Malaysia, as Singapore does not have enough space for large-scale production and storage of components.

The precasts are transported to the BTO site via trailers, and stored in a multi-storey carpark area.

Precast components ranging from three to 20 tonnes are hoisted to the upper floors to be installed. Depending on the size of the component and the surface preparation needed for installation, each piece can take between one and two hours to be completed.

Due to space constraints at the BTO site, only one temporary construction lift is placed at each block to take workers and raw materials such as cement to the upper floors. This adds to the construction time.

Cement is poured on-site for the corridor and common areas of this project that could not be precasted. The project also has sky terraces and void decks with high ceilings spanning eight floors that add to the construction complexity.

Sample units of different flat types are constructed within the project to serve as a baseline for the contractors’ quality of work. These units are checked for tile lippage – an uneven surface when two tiles are not laid on a uniform level – internal fittings and other finishes.

Stage 4: Fitting out the residential units

Sanitary fittings, windows, and wall and floor finishes are installed within the units.

This project did not get the NEA’s approval to carry out less noisy works on Sundays or public holidays to speed up the progress as it is near existing blocks and facilities.

Exterior works such as block painting, landscaping and construction of signage, drop-off porches, service roads and ramps are carried out.

Part of the existing Kempas Road had to be widened from a one-way to two-way road to meet the LTA’s requirement.

Stage 5: Inspection of the units before handing over keys to home owners – 3 months

Quality checks are conducted on each completed flat, and the HDB will rectify substandard fittings.

Regulatory documents are submitted to the authorities including the NEA, national water agency PUB, the Building and Construction Authority and the Singapore Civil Defence Force to get clearance before the HDB can hand over the keys to home owners.

Float: 6 months

The HDB caters a buffer of six months for unforeseen circumstances such as inclement weather, minor supply issues and soil factors.

Total duration taken to construct the Kempas Residences BTO project: 56 months, or four years and eight months.