HK Contractors

Sub-division of flat units (Sub-divided units)

What is "sub-divided unit"? What building safety problems may arise from building works associated with "sub-divided unit"?

"Sub-division of flat unit", i.e. commonly known as "sub-divided units", generally refers to the sub-division of a flat unit into two or more individual units. The associated building works commonly involve the removal of the original non-structural partition walls, erection of new non-structural partition walls, installation of new toilets and kitchens, alteration or addition of internal drains for the additional toilets/kitchens, as well as thickening of floor screeding to accommodate the new/diverted drain pipes, etc. The building safety and environmental hygiene may be adversely affected if these associated building works are not properly carried out, including addition of unauthorized door openings which contravene the regulations on means of escape, additions of openings for ventilation affecting the integrity of fire resisting construction, improper drainage works causing water seepage, and overloading of the building due to addition of non-structural partition walls and thickened floor screeding.

Are the building works associated with "sub-divided units" unauthorized building works (UBW) ?

Under section 41(3) and 41(3C) of the Buildings Ordinance (Cap 123) (BO), certain building works and drainage works (other than minor works) that do not involve the structure of a building can be carried out in existing buildings without prior application to the Building Authority (BA) and obtaining BA's approval. The erection of non-structural partition wall is an example of such kind of exempted building works. Erection of partition walls in domestic premises should comply with the building standards stipulated in the building regulations, including not causing overloading to the building and not affecting the means of escape in case of fire. If the building works associated with the "sub-divided units"are such kind of exempted building works and do not contravene any regulations, they are not UBW. Under the Minor Works Control System (MWCS) which was fully implemented on 31 December 2010, the internal drainage works within building units, which were commonly found in "sub-divided units", were designated as minor works. It is a contravention of the statutory requirements if the works are not carried out by prescribed registered contractors.

Will the building works associated with "sub-divided units" affect the structure of the building?

The building works associated with "sub-divided units" commonly involve the removal of the original non-structural partition walls, erection of new non-structural partition walls, thickening of floor screeding and addition of door openings. These works may overload the floor slabs, beams and even the columns of the building. The structure of the building would be adversely affected due to the addition of openings on structural walls for new doors or for new drain pipes installation. If the relevant drainage works are not properly carried out leading to water seepage, corrosion of steel reinforcement and concrete spalling at the ceiling of the flat below may occur.

What aspects of fire safety of building should be paid attention to when carrying out building works associated with "sub-divided units"?

The fire safety of a building mainly covers the provisions of proper fire resisting construction, adequate means of escape and means of access for fire-fighting and rescue. Attention should be paid to the following aspects when carrying out building works associated with "sub-divided units" :-

i)	do not remove existing fire door or replace by door not meeting the fire safety standard
ii)	If the original fire resisting door at entrance of the flat is maintained and the total number of occupants are not more than 30 persons, the clear width of the internal corridor serving the sub-divided units should not be less than 0.75m; if more than 30 persons, a minimum width of 850mm should be maintained.
iii)	If the original fire resisting door at entrance of the flat is removed or replaced by door not meeting the required fire rating, the clear width of the internal corridor serving the sub-divided units should not be less than 1.05m. Besides, the walls separating the sub-divided units from each other and the walls at both sides of the internal corridor should have a fire rating of not less than 1 hour and the door of each sub-divided unit should be self-closing, smoke sealed and have a fire rating of not less than 1 hour
iv)	do not make new door openings in the enclosure of exit staircase
v)	do not make ventilation openings to staircase enclosure affecting the means of escape
vi)	do not make openings on the fire resisting wall between the "sub-divided units"and the means of escape for installation of air-conditioner or exhaust fan
vii)	the metal gates at entrance of the "sub-divided units", if installed, should not obstruct the means of escape
viii)	the "sub-divided unit"should not block or close the means of escape leading to the secondary exit staircase

Will the building works associated with "Sub-divided units" affect the environmental hygiene of the building?

Building works associated with "sub-divided units" commonly involve installation of new toilets/kitchens, alteration or addition of internal drainage system for the new toilets/kitchens. If the works are not properly carried out, water seepage may occur and the environmental hygiene of the building may be adversely affected. Moreover, construction of new toilet/kitchen on any balcony built over the street is not permitted under the Building (Planning) Regulations.

How can the building works associated with "sub-divided units" be carried out legally?

The building works associated with "sub-divided units" are subject to the control of the Buildings Ordinance (BO). If the building works involve the structure of the building, owner should appoint an authorized person and registered structural engineer (if necessary) for preparation of plans. After obtaining the approval of the plans and consent to commencement of the works from the Building Authority (BA), the works should be carried out by a registered contractor in accordance with the approved plans. Alternatively, internal drainage works within individual building units can be carried out by prescribed registered contractor under the Minor Works Control System (MWCS) which was fully implemented on 31 December 2010. Other works involved should be exempted building works under section 41(3) and 41(3C) of the BO and do not contravene any regulations.

How can I know whether or not the building works of the "sub-divided unit" contravenes the provisions of the Buildings Ordinance ?

If the following conditions are observed at the "sub-divided units", the building works thereof could have contravened the provisions of the Buildings Ordinance:

a.	excessive thickening of floor screeding that may cause overloading
b.	cracks appear at the junction of partition wall and ceiling that may be caused by overloading
c.	cracks appear on the floor near the cantilevered balcony that may be caused by overloading of the structural member of the balcony
d.	structural members (eg beam, column or structural wall) partially removed
e.	openings on structural walls
f.	toilet/kitchen constructed on the balcony built over the street
g.	the means of escape is obstructed by doors/metal gates installed at the entrance of "sub-divided units"
h.	existing fire door is removed or replaced by door not meeting the fire safety standard, e.g. hollow core wooden door
i.	door opening of "sub-divided units"is formed in the enclosure of exit staircase/smoke lobby
j.	opening is formed connecting the "sub-divided units"with the staircase/smoke lobby
k.	the existing secondary exit staircase of the building is not accessible
l.	signs of leakage of drainage pipes
m.	signs of water seepage or concrete spalling at the ceiling of the flat below
n.	no window is provided for natural lighting and ventilation in the "sub-divided unit"for domestic use.

What should I do if I suspect that the building works associated with "sub-divided units" may contravene the Buildings Ordinance ?

If you are the owner of the premises and suspect or find out that the building works associated with "sub-divided unit"may contravene the provisions of the Buildings Ordinance, e.g. removal of structural members, blocking of the access to the existing secondary exit staircase, water seepage or concrete spalling, you should immediately consult a building professional and appoint a registered contractor to rectify the irregularities so as to protect yourself and the other tenants. You should also report the situation to the Buildings Department.

If you are a tenant of the "sub-divided unit" or intend to rent the "sub-divided unit" and discover the above-mentioned situation which may contravene the Buildings Ordinance, you should immediately ask the owner to carry out the rectification works and report the case to the Buildings Department through :-

	Telephone Hotline : 2626 1616 (Handled by '1823 Call Centre')
	Electronic Complaint Form (Online Form) Hyperlink : http://www.bd.gov.hk/english/services/enquires.html
	Postal address : 12/F., Pioneer Centre, No. 750 Nathan Road, Kowloon
	Email address : enquiry@bd.gov.hk

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