BHU Minimum Floor Area
& Ceiling Height Requirements
Floor area and ceiling height are the two most frequently asked — and most frequently failed — BHU certification standards. This guide explains exactly how each is measured, and what landlords can do when a unit falls short. These are just 2 of the 6 technical requirements set out in the BHU minimum living standards.
| Standard | Minimum | Measurement Basis |
|---|---|---|
| Internal Floor Area | ≥ 8 m² | Bathroom included |
| Clear Ceiling Height | ≥ 2.3 m | Floor to ceiling; a separate ≥ 2 m standard applies below any beam |
Source: Basic Housing Units Ordinance (Ordinance No. 41 of 2025), Schedule 1, sections 1 and 2
Minimum Floor Area: How Is 8 sq m Calculated?
The ordinance defines the minimum as 8 sq m of internal floor area — the total space within the unit's internal walls. This includes the bathroom:
- Included: sleeping area, living space, kitchen area (if within the unit), entrance passageway, bathroom
- Measurement method: internal wall face to internal wall face (actual dimensions, not GFA from floor plans)
⚠️ Common Misunderstanding
"My floor plan shows 8.5 sq m — I don't need an on-site measurement, right?" That's not a safe assumption. Floor plan figures can differ from actual on-site measurements due to wall thickness and measurement methodology. A specified professional's on-site measurement is the only legally valid standard.
Which Units Most Commonly Fall Short?
Based on Owl Square Group's on-site assessment records, the following unit types most frequently fail the floor area requirement:
- Pre-1980s tenement buildings with heavily subdivided floors — habitable areas of 6–7.5 sq m are common (Owl Square case data, 2018–2026)
- Storage rooms or domestic helper quarters converted to rental units
- Over-subdivided floors (e.g. a 500 sq ft flat cut into five units, Owl Square case data, 2018–2026)
Ceiling Height: Where Is 2.3m Measured?
The Ordinance sets two thresholds: the height measured from the floor to the ceiling must be at least 2.3 metres; and where the unit contains a beam, the height measured from the floor to the underside of that beam must be at least 2 metres (Schedule 1, section 2). The measurement location therefore has several traps:
- Floor to ceiling: at least 2.3 m
- Below a beam soffit: at least 2 m
- A false ceiling is the ceiling: 2.3 m applies
- Below AC ducts or light troughs: not a Schedule 1 requirement, but worth measuring
- Rooftop structures & loft conversions
- Sloped ceilings (top-floor units)
- Pipe/duct corridors
- Bathroom ceiling height (measured separately)
⚠️ Real Case Example
A mid-floor unit had a structural ceiling height of 2.5m, but an installed false ceiling had reduced the floor-to-ceiling height to 2.15m — below the 2.3m threshold. The false ceiling was removed and certification was granted (Owl Square case data, 2018–2026).
What to Do If the Unit Doesn't Meet the Standards?
Merge Adjacent Units
The most common solution is combining two undersized adjacent units into one larger compliant unit. While this reduces the number of rentable units, per-unit rental value typically increases, and the overall yield impact is often moderate. A specified professional must confirm feasibility before works begin.
Remove False Ceilings or Reroute Ducts
If the height deficit is caused by false ceilings, AC ducts or installations — rather than structural beams — removing them may restore compliance. Where structural beams are the cause, the more lenient 2 m standard applies below the beam soffit, but it must still be met; structural alterations are harder and require an Authorized Person's judgement.
Important: Do not alter partition walls or structural elements without an Authorized Person's assessment. Unauthorised works can jeopardise structural safety and make certification significantly harder to obtain.
Frequently Asked Questions
What is the minimum floor area for a Hong Kong BHU? Is the bathroom included?
Under the Basic Housing Units Ordinance (Ordinance No. 41 of 2025), each BHU must have an internal floor area of at least 8 square metres. The bathroom — including toilet, washbasin and shower — is included in this measurement.
Should the 8 sq m be measured from floor plans or by actual measurement?
Actual on-site measurement takes precedence — from internal wall face to internal wall face. Floor plan figures can serve as a rough guide, but the specified professional certifying the unit will rely on actual measured dimensions.
What is the minimum ceiling height for a BHU, and where is it measured?
The Ordinance sets two thresholds: the height measured from the floor to the ceiling must be at least 2.3 metres; and where the unit contains a beam, the height measured from the floor to the underside of that beam must be at least 2 metres (Schedule 1, section 2). A false ceiling forms the ceiling surface, so the 2.3-metre standard applies to it; clearance below air-conditioning ducts and light troughs is not a Schedule 1 requirement, but is worth measuring as a practical matter.
Is merging units the only option when floor area is insufficient?
Merging is the most common solution, but not the only one. If the partition walls are non-load-bearing, repositioning them may increase the floor area of individual units. Whether this is structurally feasible and whether the result would meet the standard must be determined by a specified professional on-site.
Can rooftop structures or loft spaces qualify as BHUs?
Rooftop structures and loft spaces typically face both insufficient floor area and inadequate ceiling height. Some also involve unauthorised building works that require separate resolution. An assessment by a specified professional is essential — landlords should not assume eligibility without a professional evaluation.