What Is Form MW01?
Minor Works Filing for BHU Renovations, Explained

Form MW01 is a document under the Buildings Department's minor works regime: not every BHU renovation can be treated as ordinary decoration. Where works involve 3 or more suites, toilets, brick walls, solid floors, above-ground drains or external-wall ventilation ducts, most projects must go through minor works filing procedures before work starts. This guide explains the Class I/II/III tiers, the roles of MW01 and MW02, the basic filing procedure, and how the regime relates to Housing Bureau BHU certification.

1. The Minor Works Regime in Three Minutes

Hong Kong's Buildings Ordinance (Cap. 123) provides a minor works control system that classifies building works of relatively smaller scale and lower risk into three classes — Class I, Class II and Class III — allowing them to proceed under simplified procedures instead of full plan submission. The higher the class, the greater the risk and the stricter the procedural requirements; Class I is the highest-risk tier of minor works.

For BHU landlords, the key point: constructing 3 or more suites together with toilets, brick walls, solid floors and above-ground drains is among the most common high-risk items (the Item 1.41 direction). Even if the scale seems small, such works must not be treated as ordinary decoration.

On paperwork, Forms MW01 to MW05 are the forms used under the minor works regime, with different forms for different classes and stages. Taking Class I works as an example: a notification must be submitted before work starts (this is the general purpose of MW01). This step is not "waiting for approval", but the notification must be submitted in accordance with procedure and handled by a qualified person; and after completion, certification documents (MW02 etc.) must be submitted within the prescribed period. These documents affect future certification and audits. The key point: neither the pre-start nor the post-completion paperwork can be missed.

2. Which BHU Renovation Items Require Filing

The following items are the most common categories in BHU renovation — and the most easily mistaken for ordinary decoration. Check each one before work starts:

1. 3 or more suites
   Constructing multiple suites is the core work of BHU renovation and a high-risk item. Review it along the Item 1.41 direction first, and ask about MW01 and the PBP/PRC roles.
2. Toilets
   Constructing or altering toilets involves drainage and floor loading, and is counted together with suites in terms of number and scope.
3. Brick walls
   Building brick walls involves layout alteration and may affect structure and escape routes — not ordinary finishing work.
4. Solid floors
   Raising or thickening floors increases floor loading; if the alteration is substantial, structural implications must be assessed by a professional.
5. Above-ground drains
   Altering or constructing above-ground drainage is one of the common high-risk items, considered together with toilet and kitchen alterations.
6. External-wall ventilation ducts
   Works on external walls involve the building's facade and safety, and cannot be treated as internal decoration.

Conversely, if the works involve only ordinary finishing or cleaning, they can in principle be treated as ordinary decoration — but keep photos and records, and confirm that fire safety, ventilation and utilities are not affected. Where structural walls, columns and beams or major alterations are involved, the works are beyond what the simplified minor works procedures can cover, and an AP/RSE should determine the A&A route.

3. How to File: The Basic Procedure

Minor works filing is not as simple as the landlord filling in a form — it must be handled by qualified persons following statutory procedure. The general process:

1. Engage a qualified person to determine the class
   A Prescribed Building Professional (PBP) is the commonly responsible role for Class I minor works; actual construction must be carried out by a Prescribed Registered Contractor (PRC), who must hold the appropriate minor works class, type and item qualifications. Landlords should verify these qualifications before engagement.
2. Pre-start notification
   Class I/II minor works require a notification 7 days before work starts. Note that this is not "wait for approval", but the notification must be submitted in accordance with procedure and handled by qualified persons — the paperwork cannot be skipped.
3. Post-completion documents
   After completion, MW02 and other certification documents must be submitted within a 14-day period. These documents affect future BHU certification and audits — a gap many landlords only discover afterwards.

Every unit differs (building age, existing layout, scope of works), and many items sit on the boundary between minor works and A&A. If you are unsure which route your works fall under, confirm with a registered contractor or Authorized Person before starting.

4. Minor Works ≠ BHU Certification: Two Separate Tracks

This is the most important clarification in this guide: minor works filing and BHU certification are two separate tracks, administered by two different authorities.

The practical implication: complete paperwork does not mean the certification assessment can be ignored. Having full minor works documents only means the building works procedure was compliant; the unit must independently meet the BHU living standards before certification is granted. Conversely, a renovation plan that meets certification standards may still need to go through the Buildings Department's minor works filing first if it involves minor works items. Plan both routes together before work starts — do not focus on one and miss the other.

5. The Risks of Not Filing

Treating minor works as ordinary decoration and skipping the statutory procedure has one direct consequence: missing documentation affects future BHU certification and audits. Many landlords only discover at the certification stage — after the works are done — that the pre-start notification or post-completion documents are incomplete. They then have to compile evidence of the works and site information first, and have a qualified person assess the remedial options, which costs time and money.

In addition, building works carried out without filing may constitute unauthorized building works, exposing the owner to Buildings Department enforcement. If you are unsure which category your completed works fall into or what the consequences are, confirm with a registered contractor or the Buildings Department rather than guessing.

6. Frequently Asked Questions