This document summarizes steel roof trusses. Most building roofs can be framed with prefabricated light-gauge steel trusses, which offer a high-strength, lightweight roof system that can be installed quickly. Steel trusses are manufactured from C-shaped galvanized steel and are stronger than wood trusses. They are constructed by connecting chord and web members made of steel into triangular shapes, then bolting or welding them together on the ground before installing the completed truss on the roof. All steel roofing has a protective metallic coating to prevent rusting.

1. Steel Roof Trusses
Hrishi Desai
0813

2. Introduction
Residential metal roofing is primarily
made of Steel or Aluminium. !
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Copper, zinc and titanium are also used
in specialised architectural applications
for homes.!
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Steel roofing for residential applications
is very lightweight with the heaviest
product weighing about 1.5 pounds per
square foot when installed. The products
are initially produced in giant rolls at the
steel mills.

3. Most building roofs can be framed
with engineered light-gauge steel
trusses which are manufactured
from C-Shaped metal studs.
Prefabricated steel trusses offer a
high-strength, light-weight roof
system that can be installed
quickly.
In residential construction, wood
trusses still dominate the industry,
however light gauge steel roof
systems are gaining ground in
markets where additional strength
is needed, or where greater free
spans are required.

4. Truss
A standard truss is a series of triangles : a stable geometric shape
that is difficult to distort under load. Regardless of its overall size
and shape, all the chords and webs of a truss form triangles.
These triangles combine to distribute the load across each of the
other members, resulting in a light structure that is stronger than
the sum of the strength of its individual components.
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Some of the Steel roof Trusses generally used are - King post,
Queen post, Fink, Howe, Pratt, Warren, Fan and North Light.
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5. Text

6. Roof truss strength derives from the triangle shapes that
comprise the truss itself. Triangles are naturally rigid
geometric shapes that resist distortion.
Top chords are in compression and push out at the heel
and down at the peak. The bottom chord is normally in
tension to resist outward thrust.
The webs form smaller triangles that strengthen the
overall structure and provide rigidity. Loads on the
individual webs can be either compression or tension,
depending on the type of load.

7. Text
Example of a Truss

8. Specifying a Truss
Trusses are manufactured from C-Shaped Galvanised steel. The strength of
each member derives from its geometry, rather than weight.
When specifying a roof system with a truss manufacturer, the builder/developer
should include the span of the roof, the pitch, the top-chord overhang,
the end cut and soffit return details needed, and any gable-end preferences.
Typical stresses in a roof system show some members under compression and
others under tension. When specifying a truss to a manufacturer, there are a
number of items the building designers need to provide. Most truss
manufacturers will provide the building designer with a checklist that describes
the details needed to initiate a truss design. Those details are summarised
below.

9. Text
C Shaped
Galvanised Steel
Loads acting on
A Truss

10. Construction Process
As with any structural
member, a faulty design will
undermine even the most
professional of installations.
Your roof truss will need to
be able to handle the
expected dead loads and
live loads on your structure's
roof. The truss will also need
to be supported adequately
at its ends.

11. The roof truss will have a
horizontal lower chord,
and 2 angled upper
chords that follow the roof
line. These chords will be
connected by "web"
members, which will be
oriented to form triangles.
Your design should call for
the same size lumber for
each member.
Web
Upper Chord
Lower Chord

12. Lay the truss members
out on the ground
Once all the chord and
web members are cut to
size, arrange them flat on
the ground in the shape of
the truss.
And there after, they are
bolted or joined by
welding.

13. After the truss is been bolted
up, it is lifted and placed as
per the plan.
And this way, one by one,
after placing them all, the
structure is ready.
At last, this is followed by
covering the top with the
material according to the use.

14. Protection (Metallic Coating)
All Steel Roofing has a protective barrier on both sides of the sheet
called a metallic coating which protects against rusting. This is
underneath and separate from any paint which imparts colour to the
product. There are two types of metallic coatings used:
Galvanised : This is 100% Zinc in various thicknesses depending
upon the product usage.
Galvalume or Zincalume : A mixture of aluminium and zinc. (55
percent by volume aluminium)
Metallic coatings "sacrifice" themselves to protect the Iron (Fe) in steel
from oxidation when exposed to the air and moisture is present.

16. Hrishi Desai
0813
Thank You!