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.
| Standard | Minimum | Measurement Basis |
|---|---|---|
| Internal Floor Area | ≥ 8 m² | Bathroom included |
| Clear Ceiling Height | ≥ 2.3 m | Measured at lowest point |
Source: Landlord and Tenant (Consolidation) (Amendment) Ordinance 2025 · Buildings Department Technical Guidelines
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. An Authorized Person'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
- Storage rooms or domestic helper quarters converted to rental units
- Over-subdivided floors (e.g. a 500 sq ft flat cut into five units)
Ceiling Height: Where Is 2.3m Measured?
Ceiling height is the standard landlords most often overlook — because the measurement location has several traps:
- Floor to ceiling at lowest point
- Below structural beams
- Below air-conditioning ducts
- Below light troughs or false ceilings
- 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 a false ceiling and air-conditioning duct installation had reduced the clear height at one point to 2.15m — below the 2.3m threshold. The false ceiling was removed and certification was granted.
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. An Authorized Person 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, options are more limited 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 Buildings Department (and any Authorized Person certifying the unit) will rely on actual measured dimensions.
Where exactly is ceiling height measured?
At the lowest point within the habitable space — including below structural beams, AC ducts, false ceilings and light troughs. If any occupied area falls below 2.3m, the unit does not meet the standard.
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 an Authorized Person 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 Authorized Person assessment is essential — landlords should not assume eligibility without a professional evaluation.