Building Design and Construction Handbook - Merritt - Ventech!

1.38 SECTION ONE
with noncombustible, combustible, or hazardous contents; schools; hospitals and
nursing homes; and places of assembly, such as theaters, concert halls, auditoriums,
and stadiums.
Type of construction of a building is determined, in general, by the fire ratings
assigned to its components. A code usually establishes two major categories: combustible
and noncombustible construction. The combustible type may be subdivided
in accordance with the fire protection afforded major structural components and the
rate at which they will burn; for example, heavy timber construction is considered
slow-burning. The noncombustible type may be subdivided in accordance with the
fire-resistive characteristics of components.
Building codes may set allowable floor areas for fire-protection purposes. The
limitations depend on occupancy group and type of construction. The purpose is
to delay or prevent spread of fire over large portions of the building. For the same
reason, building codes also may restrict building height and number of stories. In
addition, to permit rapid and orderly egress in emergencies, such as fire, codes limit
the occupant load, or number of persons allowed in a building or room. In accordance
with permitted occupant loads, codes indicate the number of exits of adequate
capacity and fire protection that must be provided.
1.11 ZONING CODES
Like building codes, zoning codes are established under the police powers of the
state, to protect the health, welfare, and safety of the public. Zoning, however,
primarily regulates land use by controlling types of occupancy of buildings, building
height, and density and activity of population in specific parts of a jurisdiction.
Zoning codes are usually developed by a planning commission and administered
by the commission or a building department. Land-use controls adopted by the
local planning commission for current application are indicated on a zoning map.
It divides the jurisdiction into districts, shows the type of occupancy, such as commercial,
industrial, or residential, permitted in each district, and notes limitations
on building height and bulk and on population density in each district.
The planning commission usually also prepares a master plan as a guide to the
growth of the jurisdiction. A future land-use plan is an important part of the master
plan. The commission’s objective is to steer changes in the zoning map in the
direction of the future land-use plan. The commission, however, is not required to
adhere rigidly to the plans for the future. As conditions warrant, the commission
may grant variances from any of the regulations.
In addition, the planning commission may establish land subdivision regulations,
to control development of large parcels of land. While the local zoning map specifies
minimum lot area for a building and minimum frontage a lot may have along
a street, subdivision regulations, in contrast, specify the level of improvements to
be installed in new land-development projects. These regulations contain criteria
for location, grade, width, and type of pavement of streets, length of blocks, open
spaces to be provided, and right of way for utilities.
A jurisdiction may also be divided into fire zones in accordance with population
density and probable degree of danger from fire. The fire-zone map indicates the
limitations on types of construction that the zoning map would otherwise permit.
In the vicinity of airports, zoning may be applied to maintain obstruction-free
approach zones for aircraft and to provide noise-attenuating distances around the