APP-98 - Buildings Department

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Buildings Department
Practice Note for Authorized Persons,
Registered Structural Engineers and
Registered Geotechnical Engineers
Lighting and Ventilation for Bathrooms
and Lavatories in Domestic Buildings
To promote the cause of environmental protection, the argument has often
been made that flexibility should be allowed in administering Regulation 36 of the
Building (Planning) Regulations (B(P)R) in relation to the provision of windows for
bathrooms and lavatories in domestic buildings. The Building Authority (BA) takes a
sympathetic view on this argument having regard to advances in ventilation technology
and the need for greater freedom in the design of buildings.
The BA will give favourable consideration to an application for
modification of Regulation 36 of the B(P)R in respect of internal bathrooms and
lavatories where the following criteria are met :
The room is part of a unit of accommodation for domestic use;
The room is of a reasonable size; and
The modification to be granted is unlikely to result in standards of
public health and safety being compromised.
Upon the granting of a modification of Regulation 36 of the B(P)R, the BA
will impose the following conditions :
a system of artificial lighting and mechanical ventilation
producing 5 air changes per hour is in operation at any time when
the room is in use. The change of air shall be with the outside of
the building and to achieve this, the use of ventilation ducting
provided with access for cleaning is acceptable;
there is additional permanent ventilation to the ‘open air’
complying with Regulation 2 of the B(P)R, to the ‘external air’
complying with Regulation 31 of the B(P)R or with another room
which is provided with a window meeting the area requirement
for the combined rooms. The permanent ventilation may be in
the form of a ventilation duct with access for cleaning or an
aperture in a wall or in a door, which should be suitably located
and permanently open or protected with lourves having a
minimum size of 1/20 of the floor area of the room;
- 2 -
unless demountable or replaceable ventilation duct is used, at
least one access door or panel of minimum size 150 mm x 225mm
(for ventilation duct of size 150 mm x 150 mm or above), or 100
mm x 225 mm (for ventilation duct of size under 150 mm x 150
mm) shall be provided for every 4 metres of the ventilation duct
at easily accessible location and at any change of direction,
adjacent to turning vanes or adjacent to dampers;
the requirements of Regulation 35A of the B(P)R and Practice
Note for Authorized Persons, Registered Structural Engineers
and Registered Geotechnical Engineers APP-27 on water heating
are compiled with, where applicable; and
each individual unit provided with internal bathrooms / lavatories
should have its own artificial lighting and mechanical ventilation
system and ventilation ducting required under items (a) and (b)
above. If a communal mechanical ventilation system and
ventilation ducting are provided to serve more than one unit,
proper management1 should be in place to ensure that the systems
are well maintained and in effective working order.
In order to maintain the ventilation ducting in hygienic condition, the ducting should
preferably be inspected and cleaned annually.
For the avoidance of doubt, this practice note is applicable to bathrooms
and lavatories in both new and existing domestic buildings for exemption from
complying with the statutory requirements.
( AU Choi-kai )
Building Authority
Ref. : GP/BREG/P/18 (VI)
This PNAP is previously known as PNAP 219
First issue
December 1997
Last revision February 2010
This revision June 2013 (AD/NB1) (Generally revamped)
The BA would normally accept that a building would have proper management if the maintenance of
the system and ventilation ducting is to be managed by a property management company upon the
occupation of the new building or completion of the alteration and addition works of the existing

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