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Roof Truss Layout:
Click here
for detailed truss layout information.
The roof is one of the
most difficult areas of the house to design because
of the 3 dimensional aspect. There are many different
roof types that can be used on this particular floor
layout. If you are having a difficult time designing
your roof, consider contacting your local truss
manufacturer for some assistance. Many of them would
gladly assist you using their special software to
design your house in 3D, hoping of course, they
will get your business for the trusses.
Engineered roof trusses
and floor trusses are different than I-joist and
dimensional lumber framing in that they are designed
to absorb all of the weight and external forces
and transfer it to specific points in the truss
that connect to the wall down to the concrete. These
forces are calculated by the computer software and
approved by a registered engineer working for the
truss manufacturer. When you design your roof using
I-joist or dimensional lumber, you must take your
design to an engineer for approval which can be
costly. Granted, there are acceptable practices
that can be followed to avoid using an engineer,
but these only pertain to standard box type houses,
not custom or unusual designs.
The cost of hand framing
as compared to engineered trusses, are close to
the same except for the need of a crane. The main
benefit for using engineered trusses is speed. Where
it would take 1 to 2 weeks and 3 people to frame
a roof, and it would only take 1 to 2 days and 2
people to install pre-fabricated trusses.
Considerations must be
taken to give all of the necessary information to
the truss designers or the engineer to make the
proper calculations. For example, air conditioning
units on the roof, forced air units in the attic,
tile, wood, metal, bituminous or shingle roofing,
and the geographical area where the house will be
built must be taken into account for snow, and any
specific details you want such as raised heels on
the trusses for extra insulation and attic ventilation,
long or short overhangs for shade. There are many
considerations to make when designing a roof, and
don’t forget to draw your section diagrams;
this is a great help to everyone.
Another area of consideration
is truss and rafter connections to each other and
to the wall like truss hangers and hurricane ties.
This information must be on your plans for the builder,
the plans examiner and the building inspector.
