They will be launched for sale in the second half of next year (2018), and the first of these flats will be completed by between the fourth quarter of 2020 and the first quarter of 2021.
In its statement, HDB said this will help young couples get their flats faster.
Priority will be given to first-time applicants. At least 95 per cent of the four-room or bigger flats will be set aside for first-time, applicants, up from the current quota of 85 per cent.
The faster times are achieved not by speeding up the construction. Instead, HDB will commence construction of selected BTO projects ahead of their sales launch.
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Tender for the construction for this first batch of 1,000 flats will be called this month (July) and construction works are expected to start at the end of the year.
They will come pre-finished, with floor, internal doors and sanitary fittings already installed, similar to existing BTOs where buyers pick these furnishings as an option under the Optional Component Scheme (OCS).
Two-room Flexi flats, meant for elderly buyers, will continue to come with fittings and furnishings designed for seniors.
Said the HDB statement: "Home seekers who prefer the flexibility of choosing their desired finishes and fittings under the OCS can apply for other BTO projects with the typical waiting time."
This will reduce the renovation works required and enable homebuyers to move into their new flats sooner, HDB added.
The statement did not say if the BTOs with shorter wait times will cost more than the typical BTO.
Besides BTO flats, HDB will also introduce a new sales mode, known as the Re-Offer of Balance Flats (ROF), to pool all unsold units from previous sale of balance flats exercises.
The first ROF will take place next month (August), and will be held twice every year after that, in February and August.
This is on top of current sale of balance flats exercises which are held twice a year, alongside the BTO exercises in May and November.
Now, there will be four chances a year for homebuyers to buy them.
At least 95 per cent will be set aside for first-timer families, with the rest going to second-timer families, said HDB.
These flats are popular among homebuyers as they are usually nearer to completion, said the statement.
The two measures were first announced during the Ministry of National Development's Committee of Supply debates in March.
"The two measures together will widen the range of housing options for first-timers, and enable them to move into their first homes sooner. HDB will monitor the response and make refinements where necessary," said HDB.
Said National Development Minister Lawrence Wong in a blog post on Wednesday: "I hope the wider range of options and more regular offer of flats will help homebuyers find a home that best suits their needs."