GFA-harmonised versus non-harmonised homes: how to compare PSF fairly

1. 1

   What regrossing means

   What changes when you regross, and what stays the same?

   Regrossing means adding back the relevant excluded area for an analytical comparison. It lets you express a harmonised home’s price on an equivalent earlier-style area basis. You can also work in the opposite direction: remove the relevant included area from the non-harmonised home.

   The purchase price stays the same. You are changing the area used in the calculation, not the price or the home’s legal size.

2. 2

   The raw PSF can point you towards the wrong conclusion

   Which of two homes is really dearer per square foot?

   Consider these two hypothetical homes. Assume they provide comparable accommodation, with balconies and wall boundaries treated consistently. The only area difference in this illustration is a 50 sq ft air-con ledge: it is within the older home’s stated strata area and outside the harmonised home’s strata area.

   At first glance, the harmonised home looks about 2.9% more expensive per square foot. But its total price is $50,000 lower, and the two PSF figures are calculated using different area bases.

   To assess the price difference properly, first deal with that measurement difference. Then compare the actual rooms, layout and ownership rights.

   Two hypothetical homes, as advertised

   Home	Size and price	Advertised PSF	The area used in the quote
   Non-harmonised home	1,000 sq ft · $2.20 million	$2,200 psf	1,000 sq ft. The stated size includes a 50 sq ft air-con ledge.
   GFA-harmonised home	950 sq ft · $2.15 million	$2,263 psf	950 sq ft. The ledge is outside the stated unit area.

   Source: Harmonisation of floor area definitions by URA, SLA, BCA and SCDF (circular DC22-09) (Urban Redevelopment Authority), Circular of 1 Sep 2022; read 22 Oct 2026. Extracted 22 Oct 2026.

   Illustration only, not actual units or a standard ledge allowance. Comparable accommodation is an assumption for explaining the calculation. An area outside a unit’s strata boundary is not privately owned as part of that unit.

3. 3

   Method 1: regross the harmonised home to an earlier-style basis

   What is the harmonised home's PSF on the earlier-style basis?

   For this illustration, add back the 50 sq ft ledge allowance that the earlier-style comparison includes:

   950 sq ft + 50 sq ft = 1,000 sq ft of comparison area.

   $2,150,000 ÷ 1,000 sq ft = $2,150 psf on the regrossed comparison basis.

   Now compare $2,150 psf with $2,200 psf. With both homes expressed on the same earlier-style area basis, the harmonised home is about 2.3% cheaper, rather than 2.9% more expensive.

   This is the value of regrossing: it separates a measurement difference from a real price difference. A buyer who simply compared $2,263 with $2,200 could wrongly dismiss the harmonised home as the dearer option.

   • Non-harmonised home
   • Harmonised home

   As advertised, the non-harmonised home is $2,200 psf and the harmonised home $2,263 psf. With both on the earlier-style area basis, the non-harmonised home is still $2,200 psf and the harmonised home $2,150 psf.

   Source: Harmonisation of floor area definitions by URA, SLA, BCA and SCDF (circular DC22-09) (Urban Redevelopment Authority), Circular of 1 Sep 2022; read 22 Oct 2026. Extracted 22 Oct 2026.

   The total prices do not change. Only the area used for the PSF comparison changes. Every area and price here is hypothetical. Illustration only. Older home: $2.20m / 1,000 sq ft, including an assumed 50 sq ft ledge. Harmonised home: $2.15m / 950 sq ft; regrossed comparison area 1,000 sq ft. Its stated strata area stays 950 sq ft. Accommodation is assumed comparable for this example; no standard conversion or ownership equivalence is implied.

   Show the data as a table

   The advertised PSF, then both on the earlier-style area basis: data table

   Comparison	Non-harmonised home	Harmonised home
   The advertised PSF	$2,200 psf	$2,263 psf
   Both on the earlier-style area basis	$2,200 psf	$2,150 psf

4. 4

   Method 2: adjust the non-harmonised home down to the same basis

   Does working the other way give the same answer?

   You can reach the same conclusion by removing the older home’s included ledge from the comparison:

   1,000 sq ft − 50 sq ft = 950 sq ft of comparison area.

   $2,200,000 ÷ 950 sq ft = about $2,316 psf.

   Compare that with the harmonised home’s $2,263 psf. The harmonised home is again about 2.3% cheaper on the common basis.

   The same two homes on each basis

   Comparison	Non-harmonised home	GFA-harmonised home
   As advertised: different area bases	$2,200 psf on 1,000 sq ft	$2,263 psf on 950 sq ft
   Both on the earlier-style basis	$2,200 psf on 1,000 sq ft	$2,150 psf on 1,000 sq ft (the regrossed comparison area)
   Both excluding the ledge	$2,316 psf on 950 sq ft (the adjusted comparison area)	$2,263 psf on 950 sq ft
   Actual purchase price, unchanged	$2,200,000	$2,150,000

   Source: Harmonisation of floor area definitions by URA, SLA, BCA and SCDF (circular DC22-09) (Urban Redevelopment Authority), Circular of 1 Sep 2022; read 22 Oct 2026. Extracted 22 Oct 2026.

5. 5

   What exactly can you add back or take out?

   Which areas should you adjust, and by how much?

   Start with the actual area schedules and plans. Identify which features are inside each unit’s stated area and which sit outside it. “GFA-harmonised” does not by itself tell you how many square feet to adjust.

   Air-con ledges: check the strata boundary

   Under the earlier rules, a ledge could form part of a unit’s strata area while qualifying for GFA exclusion. Under the harmonised rules, a ledge inside the unit’s strata boundary counts as GFA; one retained outside the unit as common property does not form part of that unit’s strata size. URA’s ledge treatment.

   If a harmonised unit already includes its ledge, adding a further ledge allowance would double-count it. If the ledge is outside the unit, any regrossing should identify the supported area and the comparison convention being used. The private ownership and maintenance arrangements still differ.

   Voids: distinguish a measured area from a floor you can use

   Some earlier strata areas included voids above double-height spaces. The harmonised strata definition excludes voids. For a comparison of actual floored accommodation, remove any verified included void from the older unit’s comparison area. Revised strata definition.

   High ceilings can be attractive, but a void is not an extra bedroom floor. If an earlier-style equivalent figure adds a void back analytically, disclose it separately rather than calling it usable space.

   Walls: do not add back the full external-wall thickness automatically

   The earlier URA GFA calculation used the full external-wall thickness, but SLA’s unit strata measurement already used a mid-wall basis. Harmonisation aligned the agencies’ measurements. The change in planning GFA does not justify a blanket full-wall add-back to an apartment’s advertised strata size. Earlier measurement boundaries; harmonised boundaries.

   Balconies and other private areas: keep the treatment consistent

   Balconies do not disappear from the unit comparison simply because a project is harmonised. Check them on both plans. You can make a separate comparison excluding balconies if that helps assess indoor space, but apply the same rule to both homes and label the result. URA’s balcony rules.

6. 6

   Two working comparisons: 5% and 7%

   If the plans give no area breakdown, what working cases can you use?

   For an initial comparison, we use 5% as a conservative regrossing assumption and 7% as a second case. Both percentages below are add-backs to the harmonised home’s stated area. This shows whether an apparent PSF premium remains after allowing for a possible measurement difference.

   For the same hypothetical 950 sq ft home priced at $2.15 million:

   Two working comparisons for the same hypothetical home

   Regrossing assumption	Comparison area	Comparison PSF
   5% · conservative case	950 × 1.05 = 997.5 sq ft	About $2,155 psf
   7% · second case	950 × 1.07 = 1,016.5 sq ft	About $2,115 psf

   Source: Harmonisation of floor area definitions by URA, SLA, BCA and SCDF (circular DC22-09) (Urban Redevelopment Authority), Circular of 1 Sep 2022; read 22 Oct 2026. Extracted 22 Oct 2026.

   Both percentages are add-backs to the harmonised home’s stated area of 950 sq ft, priced at $2.15 million.

   Percentage add-back versus percentage exclusion+

   A 5% add-back to 950 sq ft gives 997.5 sq ft. A 5% exclusion from an earlier 1,000 sq ft leaves 950 sq ft; reversing that requires 950 ÷ 0.95 = 1,000. These are different percentage bases.

   The earlier worked example adds exactly 50 sq ft. That is 5% of the older home’s 1,000 sq ft, or about 5.26% of the harmonised home’s 950 sq ft. The two working cases above instead apply exactly 5% and 7% to the harmonised area. Keep the chosen basis stated throughout a comparison.

7. 7

   A practical way to compare your shortlist

   What do you check, and in what order?

   1. Record the exact home and price. Use a dated price for the chosen unit, floor and facing, with relevant incentives stated.
   2. Confirm the measurement regime and stated strata area. Do not decide the regime from the showflat opening year alone.
   3. List the actual area differences. Check ledges, voids and other inclusions against the plans and schedules. Avoid counting an area twice.
   4. Put both prices on one common area basis. Show the original PSF, adjustment and comparison PSF together.
   5. Return to the home itself. Compare bedroom dimensions, furniture fit, circulation, storage, balcony use, ownership rights and total budget.

   A regrossed comparison can correct a misleading PSF premium. It cannot turn a poor layout into a good one, or make two different locations and views equivalent. Nor does a nominal size gap establish that the newer home has identical living space.

   The separate GLS land-cost article covers acquisition trends and the delay before later sites become sales launches.

Case studies and videos where this decision came up.

Regrossing

Adding back the relevant excluded area for an analytical comparison. It lets you express a harmonised home’s price on an equivalent earlier-style area basis. The purchase price stays the same.

Comparison area

The area used for a same-basis PSF comparison. It is not the home’s saleable or registered strata area, and it does not create additional living space.

How all research on this site is built

1. 1.
   Harmonisation of floor area definitions by URA, SLA, BCA and SCDF (circular DC22-09)

   Urban Redevelopment Authority · Period: Circular of 1 Sep 2022; read 22 Oct 2026 · Extracted 22 Oct 2026

   Harmonised GFA and strata definitions: GLS sites launched for sale from 1 Sep 2022; development applications generally from 1 Jun 2023, with transition provisions.

2. 2.
   Joint circular DC22-09, Appendix 1: previous measurement boundaries

   Urban Redevelopment Authority · Period: Read 22 Oct 2026 · Extracted 22 Oct 2026

   Previous measurement boundaries (URA's full external wall; SLA's mid-wall strata measurement).

3. 3.
   Joint circular DC22-09, Appendices 2 to 4: revised GFA and strata definitions

   Urban Redevelopment Authority · Period: Read 22 Oct 2026 · Extracted 22 Oct 2026

   Revised GFA and strata definitions, including the exclusion of voids from strata area.

4. 4.
   Joint circular DC22-09: supplementary FAQ

   Urban Redevelopment Authority · Period: Read 22 Oct 2026 · Extracted 22 Oct 2026

   Supplementary FAQ, especially Q11 to 17.

5. 5.
   Development Control handbook, gross floor area: air-con ledges

   Urban Redevelopment Authority · Period: Read 22 Oct 2026 · Extracted 22 Oct 2026

   Air-con ledges inside and outside the strata boundary.

6. 6.
   Development Control handbook, gross floor area: GFA measurement and strata boundaries

   Urban Redevelopment Authority · Period: Read 22 Oct 2026 · Extracted 22 Oct 2026

   GFA measurement and strata boundaries.

7. 7.
   Development Control handbook, gross floor area: balconies

   Urban Redevelopment Authority · Period: Read 22 Oct 2026 · Extracted 22 Oct 2026

   Balconies.