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1
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Should
my electrician drill holes for wiring through the truss
members?
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Definitely
NOT. Trusses are designed using the specific strength
values of the various sizes of lumber and any holes reduce
the strength of the truss. The only holes that should
be drilled are for laminating multiple ply girders and
to fasten bolted hangers. The details will be shown on
the engineering page for the specific truss.
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2
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How
high can my cathedral ceiling be using a roof truss?
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As
a general rule the ceiling pitch should be no more than
½ the roof pitch. Very steep pitch roofs or short
spans or a high heel design might allow for a steeper
ceiling pitch.
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3
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Can
you crane the trusses onto the top of the walls for me?
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We
can lift the trusses in bundles if certain conditions
are met:
a. Advanced notice must be given so trusses are strapped
together in bundles that are manageable.
b. Clear access must be available at the site. This will
be determined by the crane operator.
c. Trusses must not exceed 40 ft in span.
d. Framers must be on site to direct the crane operator
and assist with rigging.
Note: A fee of $250.00 per delivery will be charged for
craning.
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4
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How
important is bracing within the truss roof?
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Bracing
is an integral part of the truss assembly and falls into
3 categories. Temporary bracing during assembly of the
roof, permanent bracing of the complete roof structure
and bracing of the individual truss members (webs, bottom
cord and top cords). To see more detailed info on bracing
see our bracing section or visit the OWTFA site.
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5
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My
building drawings specify a W250 x 33 steel beam in the
basement. What is the equivalent size for an engineered
wood beam?
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There
are no direct conversions between steel beams and PSL
wood beams. The steel beams in your floor system could
be replaced with engineered wood beams. When you bring
your plans in for a floor joist takeoff let our estimator
know you would like the support beams sized. Where the
spans are within the capacity of PSL beams we will include
them in your floor quotation.
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6
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I am designing my own house. What floor and roof parameters
will result in the most economical structure? |
In
floor design the span has the most effect on cost. Try
to keep distances between supporting beams or walls to
16ft - 18 ft.. Specifying glued sub-floor and using 3/4"
span rated floor sheathing both increase the stiffness
of the floor assembly and therfore reduce the cost of
the floor joists or trusses. For a 2 story house, keeping
the bearing walls for the roof and the second floor vertically
in line with the supporting structure for the main floor
reduces the number of engineered beams required. This
applies even more so to "loft" style houses
where the roof structure is supported on the interior
walls.
The
truss design is affected primarilly by the compexity of
the roof and ceiling shape. Keeping the number of jogs
and angles to a minimum will help to reduce the cost of
trusses. Coffered ceilings add to the complexity of the
trusses and sometimes can be done more economically by
raising the wall height and framing the coffers down.
Spans in excess of 40 ft require the trusses to be designed
under Part 4 of the OBC adding to the loads and therfore
the cost. When the overall height of the roof exceeds
12 ft the trusses will probably require piggy backs which
adds to the cost of both the trusses and the installation.
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