The quantity and types (warm, cold, inverted or parapet) 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.
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
Local climatic conditions and regulations should be considered
in connection with local insulation requirements.
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
As an integral part of the roof it is vital gratings and
assemblies withstand all anticipated loads. This website 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.
Loading L15 (Light Industrial)
Areas with light vehicular traffic such as cycle ways and domestic
Loading M125 (Heavy Industrial)
Areas with vehicular traffic, such as car parks, factories,
warehouses and workshops.
Standard optional items are available such as filter buckets to
intercept debris, gravel guards, bearing pans to spread roof
loadings and underdeck clamps to secure outlet bodies.
Satin Nickel Bronze and Polished Nickel
Bronze to BS1400
Stainless Steel to BS EN 10088-1:2005 Grade
1.4301 (304) or Grade 1.4401 (316) if specified
Ductile Iron to BS EN 1563 & 1564 Cast with
the ductility of steel and more than doubling the tensile strength
of cast iron.
Aluminium LM 6 to BS EN 1559-4: 1999