The Four-Room Flat Shrank 15 Sqm. That Is Worth a Decade of Lease.

A four-room flat is not a fixed unit of measurement. The ones that came out of the ground in 1995 have a median floor area of 108 sq m. The ones built in 2021 measure 93. Same flat type, same name on the listing, fifteen square metres apart — 161 sq ft, or roughly a single bedroom.

Buyers compare those two flats on price, and sometimes on price per square foot. Neither number tells them the space is different, and the second one actively hides it.

The shrink, year by year

Take every four-room resale transaction in 2026 and group it by the year the lease started. The series is not a smooth decline. It is two sharp steps with long flat stretches between them.

The peak is 1995. The floor is 2002. Between them the standard four-room lost 18 sq m — 194 sq ft, about 17% of itself — and it has never come back. The 93 sq m that has held since 2012 is a partial recovery, not a return.

One caveat that matters, because it cuts against the easy version of this story: the 1980s stock is not uniformly large. Among 1980s-build four-room flats sold this year, Model A units run 104 sq m, New Generation units 93, and Simplified units 84. HDB was building three different four-room flats at once. "Older means bigger" is wrong as a rule; it is only reliable for the Model A stock of roughly 1988 to 1999.

Why it happened

Two documented changes bracket the drop. The Civil Defence Shelter Act 1997 required household shelters in new flats, and every HDB flat built since has one — a reinforced store room that counts towards floor area while being close to useless as living space. And the Asian Financial Crisis left HDB holding unsold stock weighted towards larger flat types, which is the backdrop to the size standards that followed.

The point here is not the cause. It is that the change was real, it was permanent, and the resale market still lists both eras under one label.

What price per square foot does to the comparison

PSF is the metric most buyers reach for when flats differ in size, on the reasonable-sounding theory that it normalises them. It does not, because price does not rise in proportion to floor area.

Fit log price against log floor area for 2026 four-room transactions, holding town, remaining lease and storey constant, and the elasticity is 0.67. A flat 10% larger costs about 6.7% more, not 10% more. So a larger flat mechanically shows a lower PSF even when it is the better-valued flat, and a smaller one mechanically shows a higher PSF.

Which means a buyer using PSF to compare a 104 sq m 1993 flat against a 90 sq m 2003 flat is reading a number that is partly just reporting which flat is bigger.

The natural experiment

The cleanest way to see it is to find towns where both eras are on sale, and compare within the town so location is held still. Four-room flats, 2026 transactions:

Woodlands is the control. Its 2000s stock happens to be the same 101 sq m as its 1990s stock, and with size held constant the entire gap between a 1990s flat and a 2000s flat collapses to 4.7% on price — a clean read on what roughly a decade of lease is worth, and consistent with the 0.99%-per-year estimate above.

Now look at Jurong West, where the two eras differ by 13 sq m. The newer flat costs S$10,000 more in total and gives up 140 sq ft. On PSF it looks 18% more expensive; on total price it looks like a bargain for the extra lease. Both readings are incomplete, and they point in opposite directions.

The trade, priced

On the 2026 median four-room flat — S$628,000, 93 sq m — the hedonic fit gives:

• 15 sq m of floor area: 10.0%, or about S$65,900
• 10 years of remaining lease: 10.4%, or about S$65,100

Those two numbers are close enough to be treated as equal. The older Model A flat and the newer flat are not offering the buyer a choice between space and lease at some favourable exchange rate. They are offering a swap at roughly par.

The five-room market is not at par. There the elasticity is 1.14 rather than 0.67, so size is worth more, not less, as it grows: 14 sq m is worth about S$102,000 against S$89,000 for a decade of lease. A buyer trading down in size to buy lease is giving up more than they get.

What to do with this

Three practical consequences.

Read the floor area before the PSF. Two flats of the same type in the same town can differ by 15 sq m, and that difference is worth about as much as the lease gap the listing is drawing your attention to.

Price the shelter honestly. A 93 sq m flat built in 2015 and a 93 sq m flat built in 1986 do not offer the same usable space, because one of them spends a few square metres on a household shelter. The transaction file cannot see this; a viewing can.

When the choice is space versus lease, it is close to a coin flip on a four-room — so decide it on the things the model cannot price. How long you intend to hold it, whether the layout suits you, and, if the lease is short, what happens to CPF usage and loan tenure as it runs down.

Figures computed from HDB's resale flat transaction dataset published on data.gov.sg, downloaded 15 September 2026. Size series uses 8,053 four-room transactions registered in 2026, grouped by lease commencement year; years with fewer than 15 transactions are excluded. Dollar values come from an ordinary least squares fit of log resale price on log floor area, remaining lease in years, storey and town fixed effects — 8,053 four-room observations (R² 0.86) and 4,287 five-room observations (R² 0.82). Floor area is HDB's recorded figure and includes the household shelter where present. Storey is the midpoint of HDB's published band. Methodology published. No spin.