Civil Engineering Reference
In-Depth Information
Purpose groups
The degree of fi re resistance and other measures that
Approved Document B may 'require' for the main
elements of construction depends to a great extent
upon the purpose to which the building is put. Buildings
are categorised into seven 'purpose groups':
1. Residential domestic
2. Residential institutional
3. Offi ce
4. Shop and commercial
5. Assembly and recreational
6. Industrial
7.
Storage (including warehouses and car parks).
Figure 9.9
Class A - complete non-combustible con-
struction, i.e. concrete or brick fl oors and walls
Appendix 9.1 provides a more detailed breakdown of
the types of premises in each purpose group.
In addition to the use of the building, the degree of
fi re resistance for any element of structure, including
compartment walls and fl oors, is the size of the building;
the particular dimensions that building control offi cers,
designers and builders need to consider are:
➤
Height of the building
➤
Total fl oor area
➤
Volume of each compartment.
9.4.4
Materials of construction
Fire resistance is often achieved in buildings due to
the inherent qualities of the building materials used.
Architects and builders select a variety of materials for
both esthetic and practical reasons. Some of the com-
mon materials used in construction are:
Figure 9.10
Class B - traditional construction, i.e. non-
combustible walls with combustible fl oors
➤
Brick and concrete
➤
Steel
➤
Plasterboard
➤
Glass
➤
Steel sandwich panels.
Brick and concrete
When using brick or concrete blocks for construction
adequate fi re resistance is achieved by ensuring the
joints at walls and ceilings are sound and providing suf-
fi cient vertical stability by the provision of piers and/or
corners. When mass concrete is used it is reinforced
with steel which provides the necessary stability.
Steel
Steel is used because it is light, strong and to a degree
fl exible. The major disadvantage of using steel for the
Figure 9.11
Class C - combustible construction, i.e. tim-
ber fl oors and walls
