BHU Compliance Renovation
Cost Estimates 2026
Fire doors, mechanical ventilation, and independent utility metering are the three most common BHU compliance renovation items. This guide covers real Hong Kong market cost ranges for 2026 and provides two case-based estimates to help landlords set realistic budgets before their assessment.
Main BHU Renovation Items: 2026 Hong Kong Market Rates
| Renovation Item | Cost Range | Notes |
|---|---|---|
| Fire Door (FD30) | HKD 3,000–5,500 each | Incl. installation; for doors to common corridors |
| Fire Door (FD60) | HKD 5,000–8,000 each | Typically required near cooking areas |
| Mechanical Ventilation System | HKD 5,000–12,000 per unit | Required if no exterior window; incl. fan & ducting |
| Independent Electricity Meter | HKD 3,000–6,000 per unit | Separate sub-meter per unit |
| Independent Water Meter | HKD 2,000–5,000 per unit | Mandatory; gas sub-meter not required by Ordinance |
| Bathroom Addition | HKD 25,000–60,000 per unit | Required if no existing bathroom |
Cost ranges are indicative 2026 Hong Kong market figures. Actual costs must be confirmed after an Authorized Person on-site assessment.
Three Factors That Drive Renovation Cost Differences
Renovation costs for subdivided units in the same building can differ by a factor of three or more. Understanding the following factors helps landlords set realistic expectations before their assessment.
1. Existing Facilities
The single biggest cost driver is what the unit already has. A unit with an independent bathroom, adequately sized windows, and basic electrical circuits may only need a fire door and ventilation system — total cost roughly HKD 15,000–30,000. A unit with no bathroom requires one to be added, and that single item often exceeds the cost of all other renovation work combined.
2. Building Age and Concealed Conditions
Pre-1980 tenement buildings commonly have deteriorated concealed wiring. Discovering that electrical systems need full replacement after opening walls is not unusual — this alone can add HKD 10,000–30,000 to the project cost. Older buildings also have more complex pipe layouts, making independent metering installation more labour-intensive than in newer developments.
3. Number of Units Renovated Simultaneously
When multiple units in the same building are renovated together, certain works — such as electrical connections and shared riser modifications — can be consolidated, reducing duplicated costs. Based on Owl Square Group's property management records, renovating four or more units simultaneously typically reduces per-unit costs by 15–25% compared to doing them one at a time.
The Three Main BHU Renovation Items
Fire Doors
BHU regulations require unit entrance doors to meet specified fire resistance ratings:
- Doors opening to common corridors: generally FD30 (30-minute fire resistance)
- Doors adjacent to cooking areas: FD60 (60-minute fire resistance)
FD30 fire doors including installation cost approximately HKD 3,000–5,500 each; FD60 approximately HKD 5,000–8,000 each. Cost variation depends on door size, swing direction, and existing wall construction.
⚠️ Common Misunderstanding
Many landlords assume a standard wooden door fitted with a fire-resistant board will qualify. In fact, FD30/FD60 is a complete rated system — door leaf, frame, and hardware combined — that must carry a Buildings Department-accepted fire rating certificate. Retrofitting ordinary doors does not meet the requirement.
Mechanical Ventilation System
According to the Housing Bureau's BHU Code of Practice, mechanical ventilation (Option B) is required when a unit cannot meet natural ventilation standards. The system must achieve:
- Living spaces: ≥ 5 air changes per hour (ACH)
- Bathroom: ≥ 5 air changes per hour (ACH)
- Exhaust must discharge directly to the exterior — not into common corridors
Note: The BHU Code of Practice was in draft form as of December 2025. Verify against the confirmed version published by the Housing Bureau before commencing works.
Installation costs HKD 5,000–12,000 per unit, covering the exhaust fan, ducting, and electrical controls. Higher costs occur when ducting must pass through multiple partitions or when the shared exhaust riser requires modification.
Independent Utility Metering
Each BHU must have independent electricity and water meters to ensure tenants are individually billed for their consumption:
- Electricity sub-metering: HKD 3,000–6,000 per unit
- Water meter (mandatory): HKD 2,000–5,000 per unit (varies by pipe distance)
Gas sub-metering is not a statutory requirement under the BHU Ordinance. Landlords with gas-supplied units should confirm requirements with their gas utility company (Towngas / Hong Kong and China Gas).
Note: if the building's main electrical supply capacity is insufficient, an upgrade may be required — an additional cost outside these ranges. Landlords should check with CLP or HK Electric before finalising budgets.
Case-Based Cost Estimates
The following two cases are based on Owl Square Group's on-site property management records. Figures are estimates for reference only.
1990s residential building, ground floor, 3 subdivided units of approx. 120 sq ft each, with independent bathrooms and small windows
| Renovation Item | Estimated Cost (per unit) |
|---|---|
| Fire door (FD30 × 1) | HKD 4,500 |
| Mechanical ventilation (insufficient window area) | HKD 7,000 |
| Electricity sub-metering | HKD 4,000 |
| Water meter | HKD 2,500 |
| Per-unit total | HKD 18,000 |
| All 3 units combined (estimate) | approx. HKD 54,000 |
1970s tenement building; original subdivided units had no independent bathroom; full compliance renovation required
| Renovation Item | Estimated Cost (per unit) |
|---|---|
| Bathroom addition (incl. plumbing & electrical) | HKD 40,000 |
| Fire door (FD30 × 1) | HKD 5,000 |
| Mechanical ventilation | HKD 9,000 |
| Electricity sub-metering | HKD 5,000 |
| Water meter | HKD 3,000 |
| Per-unit total | HKD 62,000 |
⚠️ Important
The figures above are cost estimates for reference only and do not constitute a quotation or contractual commitment. Actual costs must be determined by an Authorized Person assessment of the specific renovation scope, followed by a formal contractor quotation.
One Thing Landlords Must Do Before Renovation
Do not start works before an Authorized Person has assessed your unit. A common and costly mistake is engaging a contractor before obtaining an AP assessment. This creates three problems:
- The scope of works must match the AP's design drawings — unapproved works may need to be demolished and redone
- Fire doors, ventilation systems, and certain structural modifications are prescribed works that require AP supervision and sign-off
- Starting works without approval may complicate or invalidate the certification application
The correct sequence: AP on-site assessment → Determine scope & produce design drawings → Engage compliant contractor → AP confirms completion → Submit certification application to the Buildings Department
Frequently Asked Questions
How much does BHU compliance renovation typically cost in Hong Kong?
Renovation costs vary significantly based on the unit's existing condition. Units that already have an independent bathroom and only need a fire door and mechanical ventilation system typically cost HKD 15,000–30,000 per unit. Units that require a bathroom to be added can cost HKD 60,000–100,000 per unit. An Authorized Person (AP) assessment is required to determine the exact scope before any works begin.
What fire door rating is required for BHU certification, and what does it cost?
According to Buildings Department technical requirements, doors opening to common corridors generally require FD30 (30-minute fire resistance rating), while doors adjacent to cooking areas typically require FD60 (60-minute rating). FD30 fire doors including installation cost approximately HKD 3,000–5,500 each; FD60 doors cost approximately HKD 5,000–8,000 each.
When is mechanical ventilation required, and what does it cost?
Mechanical ventilation is required when a subdivided unit has no window to the exterior, or when the window area is less than 1/10 of the unit's floor area. Under Option B of the BHU Code of Practice, the system must achieve ≥5 air changes per hour (ACH) for living areas and ≥5 ACH for bathrooms. Installation typically costs HKD 5,000–12,000 per unit depending on ducting complexity.
Is independent utility metering mandatory for BHU certification?
Yes — each BHU must have an independent electricity meter and water meter. Electricity sub-metering costs approximately HKD 3,000–6,000 per unit; independent water meter installation costs approximately HKD 2,000–5,000 per unit depending on existing pipe locations. Gas sub-metering is not a statutory requirement under the Ordinance; landlords with gas-supplied units should confirm requirements with their gas utility company.
Can renovation costs change after an Authorized Person assessment?
Yes, they can. The AP assessment determines the scope of required works, but concealed issues discovered during construction — such as deteriorated wiring or corroded pipes in older buildings — may increase costs. It is advisable to budget a 10–15% contingency and to confirm with contractors whether their quotes cover concealed works.