How saleable area is measured and what it includes

The saleable area of a Hong Kong residential property is measured to the exterior face of the enclosing walls that bound the flat itself. Where a wall separates your flat from a neighbour’s, the measurement is taken from the middle of that party wall. This rule is set out in Section 8 of the Residential Properties (First-hand Sales) Ordinance (Cap. 621), which governs all first-hand residential sales. The area includes the floor space of any balcony, utility platform or verandah that forms part of the property, but explicitly excludes ten specific items — even when they are part of the property you buy. The key point: saleable area is not the total floor area you can walk on. It is a regulated figure designed to give you a consistent basis for comparing flats in different developments, but it deliberately omits certain features that still add value to your home.

How the measurement works in detail

For a flat within a building, the measurement starts at the outer surface of the external wall. If your flat has a wall that is also the building’s exterior, the measurement is taken from the outside face of that wall, including the thickness of the wall itself. For internal walls shared with an adjoining flat, the measurement stops at the centre line of the wall — the mid-point of its thickness. This ensures that the area of the party wall is not counted twice between two properties.

A balcony, utility platform or verandah that is enclosed by walls and belongs to your flat is measured in the same way: from the exterior of its own enclosing walls. Its floor area is then added to the flat’s main floor area to arrive at the total saleable figure. However, the law requires that any balcony or utility platform area be stated separately in the sales brochure and price list. You will see a line such as “Balcony: 4.5 m²” and “Utility platform: 1.2 m²” alongside the main saleable area figure.

What is excluded from saleable area

The ordinance lists ten items in Part 1 of Schedule 2 that must be excluded from saleable area, even when they physically form part of your property or are included in the sale. These ten are:

• Air-conditioning plant room
• Bay window
• Cockloft
• Flat roof
• Garden
• Parking space
• Roof
• Stairhood
• Terrace
• Yard

If your flat has any of these features, the vendor must list each one separately in the brochure and price list, showing its floor area. For example, a flat with a bay window will show a line “Bay window: 1.8 m²”. But that area is not added to the saleable area. It is an additional figure you can use to judge the total usable space, but it is not part of the official saleable figure for pricing purposes.

Why second-hand listings are different

The strict statutory definition applies only to first-hand residential property sales — that is, flats sold by a developer who has never been occupied. Once a flat is resold, the vendor is not legally required to use the same measurement rules in their advertising or price lists. In practice, many second-hand listings quote a “saleable area” figure, but that figure may be calculated differently from one agent to another. Some may include bay windows, others may not. Some may use internal wall surfaces rather than the centre of party walls. There is no central registry that checks second-hand area figures for accuracy.

What to verify: when viewing a second-hand flat, ask the agent or owner what the source of the area figure is. The most reliable reference is the “saleable area” stated on the first-hand sales brochure or the assignment (the legal deed of sale) from when the flat was originally sold by the developer. If the property was built before the current ordinance took effect (the rules have applied to all first-hand sales since 2013), the original brochure may use different terminology. In that case, you can compare the flat’s physical dimensions with the listed area to gauge whether the figure seems reasonable. For properties where the original developer’s documentation is unavailable, you have no guarantee the figure conforms to the statutory definition.

The “efficiency ratio” — unofficial but widely used

You will often hear agents refer to a flat’s “efficiency ratio” (實用率), usually calculated as saleable area divided by gross floor area (GFA). This ratio is not defined by any statute. There is no official formula and no prescribed figure. Moreover, because the first-hand sales ordinance prohibits vendors from stating gross floor area in their brochures or price lists, you cannot compute an official efficiency ratio for a new development from the developer’s materials alone. If you want to calculate it yourself, you would need the GFA figure from the building’s approved plans or from the Land Registry’s records, but those documents are not provided with the sales material. The efficiency ratio you hear in the market is therefore an informal estimate, and you should treat it as a rough guide only, not a precise legal measure.

The one-figure rule in first-hand marketing

Under Sections 23(1) and 31(9) of the ordinance, a vendor of a first-hand residential property must not include any area figure in the brochure or price list other than the saleable area and the ten excluded items. This means you will not see a gross floor area, a carpet area, or any other total in the official sales documents. The purpose is to prevent confusion and to standardise the only figure that buyers can compare across developments. If you see a “gross floor area” quoted in a first-hand advertisement, it is either a mistake or a violation of the law.

Practical implications for your purchasing decision

When you review a first-hand sales brochure, the saleable area is the number you should use to compare the size of different flats. But remember that the saleable area excludes bay windows, plant rooms, terraces and the like. A flat with a 5 m² terrace and a 3 m² bay window will have a saleable area that looks the same as a flat without those features, yet the first flat offers more usable external space. Always check the separate list of excluded items to see what extra space you are actually getting.

What to check or do next

• For a first-hand flat: confirm the saleable area figure and the separate areas of any balcony, utility platform, verandah, and the ten excluded items. These figures must appear in the sales brochure and price list. Cross-check them against the Sales of First-hand Residential Properties Authority (SRPA) website or the ordinance itself (Cap. 621) if you have any doubt.
• For a second-hand flat: ask for the original first-hand sales brochure or the assignment. If neither is available, ask the agent to state in writing how they calculated the saleable area figure. Accept no verbal assurance; get it documented.
• Visit the SRPA website (www.srpa.gov.hk) for the official FAQs on area measurement and the full text of the ordinance. The authority publishes a useful PDF titled “Frequently Asked Questions on Areas of Residential Properties” that explains the measurement rules in simple terms.
• If you are comparing two flats, one first-hand and one second-hand, remember that the second-hand figure may not follow the same rules. Ask for the measurement method before making a decision.