Frost Brochure Issue 03 - Catalog - Page 66
Roof Drains - Design Considerations
FLOW RATE
THERMAL INSULATION
The quantity and types of roof outlet
to be used in a given application
must be related to the roof area and
anticipated volume of rainwater to be
drained.
Flow rate is the maximum amount
of water (litres/second) which a roof
outlet will drain and is influenced by
several factors: grating free area (i.e.
gaps in the grating), sump size, body
free area, design of the outlet, outlet
size and additional accessories such
as gravel guards and filter buckets.
Flow rates of Frost roof outlets are
shown as the square metre area
drained per outlet based on a head of
water of 35mm and a rainfall intensity
of 75mm per hour (0.021 litres /
second/sq.m).
The roof outlet size and piping
system size relate to each other
and should be within recognised
parameters.
Local climatic conditions and
regulations should be considered
in connection with local insulation
requirements.
PIPEWORK
The type and size of pipework in an
installation is fundamental to the
correct selection of roof outlets.
Frost roof outlets can be connected
to all pipework in general use
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MATERIALS AND APPEARANCE
Strength, corrosion resistance and
discreet appearance are important
considerations when making roof
outlet selections.
For areas such as balconies or roof
terraces products are available in
nickel bronze, ductile iron, stainless
steel or aluminium materials. Drains
located in pedestrian surfaces or
access routes must be disabled
compliant.
WEIGHT BEARING AND LOAD
RATING
As an integral part of the roof it
is vital gratings and assemblies
withstand all anticipated loads. This
catalogue shows the load rating
class for each grating, cover or gully
assembly based on BS EN 1253, as
follows:
Loading K3 (Pedestrian Only)
Areas for foot traffic only, such as
washrooms, shower areas, hotels,
schools, museums, retail centres,
swimming baths, leisure centres,
balconies, terraces and roof gardens.