11.1This section describes additional considerations which apply to the design and construction of car parks and shopping complexes.
11.2Buildings or parts of buildings used as parking for cars and other light vehicles are unlike other buildings in certain respects which merit some departures from the usual measures to restrict fire spread within buildings. Those are:
- aThe fire load is well defined; and
- bWhere the car park is well ventilated, there is a low probability of fire spread from one storey to another. Ventilation is the important factor and, as heat and smoke cannot be dissipated so readily from a car park that is not open-sided, fewer concessions are made. The guidance in paragraphs 11.3 to 11.6 is concerned with three ventilation methods: open-sided (high level of natural ventilation), natural ventilation and mechanical ventilation.
Open-sided car parks
11.3If the building, or separated part containing the car park, complies with the following provisions it may be regarded as an open-sided car park for the purposes of fire resistance assessment in Appendix A, Table A2. The provisions are that:
- athere should not be any basement storeys;
- beach storey should be naturally ventilated by permanent openings at each car parking level, having an aggregate vent area not less than 1/20th of the floor area at that level, of which at least half (1/40th) should be equally provided between two opposing walls;
- cwhere one element of structure supports or carries or gives stability to another, the fire resistance of the supporting element should be no less than the minimum period of fire resistance for the other element (whether that other element is loadbearing or not).
- dif the building is also used for any other purpose, the part forming the car park is a separated part and the fire resistance of any element of structure that supports or carries or gives stability to another element in the other part of the building should be no less than the minimum period of fire resistance for the elements it supports; and
- eall materials used in the construction of the building, compartment or separated part should be non-combustible, except for:
- iany surface finish applied to a floor or roof of the car park, or within any adjoining building, compartment or separated part to the structure enclosing the car park, if the finish meets all relevant aspects of the guidance on requirements B2 and B4;
- iiany fire door;
- iiiany attendant’s kiosk not exceeding 15m2 in area; and
- ivany shop mobility facility.
Car parks which are not open-sided
11.4Where car parks do not have the standard of ventilation set out in paragraph 11.3(b), they are not regarded as open-sided and a different standard of fire resistance is necessary (the relevant provisions are given in Appendix A, Table A2).
Such car parks still require some ventilation, which may be by natural or mechanical means, as described in paragraphs 11.5 or 11.6 below.
11.5Where car parks that are not open-sided are provided with some, more limited, natural ventilation, each storey should be ventilated by permanent openings (which can be at ceiling level) at each car parking level. These should have an aggregate free vent area not less than 1/40th of the floor area at that level, of which at least half should be split equally and provided between two opposing walls (1/160th on each side). (See Approved Document F Ventilation for additional guidance on normal ventilation of car parks.)
11.6In most basement car parks and in enclosed car parks, it may not be possible to obtain the minimum standard of natural ventilation openings set out in paragraph 11.5. In such cases a system of mechanical ventilation should be provided as follows:
- athe system should be independent of any other ventilating system (other than any system providing normal ventilation to the car park) and be designed to operate at 10 air changes per hour in a fire condition. (See Approved Document F Ventilation for guidance on normal ventilation of car parks);
- bthe system should be designed to run in two parts, each part capable of extracting 50% of the rates set out in (a) above and designed so that each part may operate singly or simultaneously;
- ceach part of the system should have an independent power supply which would operate in the event of failure of the main supply;
- dextract points should be arranged so that 50% of the outlets are at high level and 50% at low level; and
- ethe fans should be rated to run at 300degC for a minimum of 60 minutes and the ductwork and fixings should be constructed of materials having a melting point not less than 800degC.
For further information on equipment for removing hot smoke, refer to BS EN 12101-3:2002.
An alternative method of providing smoke ventilation from enclosed car parks is given BS 7346-7:2006
11.7Whilst the provisions in this document about shops should generally be capable of application in cases where a shop is contained in a single separate building, the provisions may not be appropriate where a shop forms part of a complex. These may include covered malls providing access to a number of shops and common servicing areas. In particular, the provisions about maximum compartment size may be difficult to meet, bearing in mind that it would generally not be practical to compartment a shop from a mall serving it. To a lesser extent, the provisions about fire resistance, walls separating shop units, surfaces and boundary distances may pose problems.
11.8To ensure a satisfactory standard of fire safety in shopping complexes, alternative measures and additional compensatory features to those set out in this document are appropriate. Such features are set out in Sections 5 and 6 of BS 5588-10:1991 and the relevant recommendations of those sections should be followed.