Benefits of Awnings & Canopies
Frequently Asked Questions
Design Loads for Awnings & Canopies
Fabric Cleaning Instructions
Technical Information - Awning Frames
Technical Information - Fabric
Design Loads for Awnings
Load for which awning and canopies may need to be designed can be
categorized as follows:
This is the self-weight of the awning or canopy frame, fabric and
hardware. This load must always be included with other design loads since
it is always acting on the structure. For instance, if one were designing
an awning for 20 psf snow load, and the structure itself weighed 2 psf,
then the design for snow should actually account for 22 psf total load.
This load, as well as snow load, are usually the most critical loads on
awnings and canopies.
Important aspects of wind load are:
A. Speed or Velocity
Basic wind pressure is a function of its speed. Basic wind pressure (psf)
can be computed as the product of 0.00256 times the square of the wind
speed (mph). It can be readily observed then, for example, that the wind
forces on an awning are four times greater if the wind speed is doubled,
and the forces are nine times greater if the wind speed is tripled.
Design wind speeds are generally shown on maps published in the building
code. Local codes may require higher design wind speeds.
This is a general category for the amount of protection from the wind
that is afforded by the surrounding environment. Structures located in
wooded areas, for instance, do not have to be designed for as much wind
force as a structure located in an open area.
These are short-term excursions of velocity above the steady design
velocity, which must be accounted for in the design.
D. Drag, Lift
Drag is the wind-induced pressure toward the fabric surface, and lift is
the pressure away from the fabric surface. Wind forces on an awning
system act in different directions (toward or away from the fabric
surface depending on a variety of factors). When designing an awning
frame, all these factors must be taken into account.
E. Return Period
This term is used to describe the time interval which is the basis for
establishing the required design wind speed. For most applications the
return period is 50 years. This simply means that the required design
wind speed is that which has a 0.02 statistical probability of occurring
once in 50 years. Loss and safety experts have determined that it is an
acceptable level of risk and have based code design requirements on it.
Required design snow loads are established by maps published in the
building code. As in the case for wind, sometimes local requirements are
more stringent. On the other hand, in many localities there is no
requirement for snow load design. Check with the local department of
building and safety.
Some important considerations about designing for snow are:
A. Ground Snow
The beginning point for snow design, this is the pressure of the designed
snow load occurring at ground level.
A categorization of the amount of protection afforded by the
surroundings. interestingly, the exposure factor works opposite of the
way it works for wind. Whereas a wooded environment would result in a
lowering of the wind forces on a structure, a wooded environment would
result in higher snow loads than an open environment would.
C. Flat Roof Snow Load
This is the design load occurring at the actual roof level, and results
from factoring the ground snow load by a coefficient accounting for
exposure and height. Many times the flat roof snow load can be as little
as 0.6 or 0.7 times the ground snow load. For example, the snow map or
the code may indicate a 20 psf ground snow load; the actual design
pressure required for an awning may be as little as 12 psf.
Building codes require that the phenomenon of drifting snow be accounted
for in the design of roofs; this includes awnings and canopies. While it
is beyond the scope of this publication to discuss this in detail, the
effects of drifting snow can be significant. The codes describe the
procedure for designing with snow drifting in mind.
E. Return Period
See discussion under Wind Load.
These are loads that are associated with the forces related to human
occupants, furniture, equipment, etc. Since these loads are movable, the
live load stipulation is an allowance for the most severe anticipated
condition or case. Common code requirements for roof live loads are from
12 to 20 psf. Provided that the case of ponding water is properly
addressed, live loading is not a practical requirement in the design of
awnings. Some codes do not require a live load design, and others greatly
reduce the requirement.
Addressed elsewhere in this publication, this is a potential load on an
awning or canopy and must be addressed in one of several ways:
A. Design for ponding must be taken structurally
B. Keeping the fabric properly supported and taut will avoid the problem.
C. Remove snow before it melts and ponds water.
D. All the above.
These are loads due to earthquakes or earth tremors. The design process
for earthquake loads is also too elaborate to be included in this
publication. However, awnings and canopies tend to fare well in
earthquakes for the following reasons:
A. They are lightweight; lightweight structures do not have a lot of
mass, therefore, relatively small seismic forces are likely to be
developed. F= ma.
B. They are generally small, secondary structures. Compared to the
structures to which they are attached, which are subject to significant
destructive forces due to their larger mass, these structures are
relatively unaffected. F= ma. Although seismic design requirements are
not rigorously pressed in geographical areas not significantly affected
by earthquakes, most model codes contain the provision in current