ECN Forum Forums Code Related Discussion Building Codes for Electricians Trusses

What are we allowed to do to a truss, as far as drilling, cutting, notching, altering, etc...

Ryan, I looked at some of the paperwork that came with some roof trusses the other day. It basically said no drilling, notching,notching,chopping or hacking.

If you must do one of the above,it says to consult a structural engineer.

Russell

Pretty much, any alteration to an engineered truss requires approval of the manufacturer or a competent authority (licensed professional engineer). No holes, notches, cut, etc. without written permission. Engineered beams - LVL and the like - are the same story. They usually come with installation instructions showing allowable holes.

I agree with the others.

Nothing is to be done to modify the truss in any way without an engineer signing off on it.

Once an engineer is involved you can do what ever he/she designs and signs for.

I mostly work with steel truss and we are not allowed to support off of the bottom cord on most jobs, this includes I beams too.

On these jobs the ceiling contractor must tie off to the top chord of the truss.

And if I ever took a sawzal to a steel truss the GC would have me paying for repair replacement.

[This message has been edited by iwire (edited 10-23-2003).]

In most single family homes I've worked in they've had 2 x 6 (or better) joists for the ceiling/attic floor @ 16" on center.

It's common for the Attic to be used for storage around here too. What kind of an Attic storage load would these Trusses support? Is that figured in the design of these things?

Bill

all excellent answers .it is amazing what forms of truss butchery an inspector sees during framing inspections.one person had to remove the roof and start over.they were not happy campers. sometimes the engineers cannot design a fix as was the case.think before you butcher!

Ryan,

Slightly off-topic, but here's some past discussion on Engineered Beams:
https://www.electrical-contractor.net/ubb/Forum1/HTML/000607.html
https://www.electrical-contractor.net/ubb/Forum1/HTML/000864.html

Bill

I don't remember drilling holes in trusses.

It was never allowed.

Joists were a different story.
One carpenter I talked to, said joist manufacturers had guidelines.
It was a simple math thing. Size of hole, number and spacing of holes, width of joist, distance of holes from center or end, span of joist.........etc.

It sounds confusing, but the math is like sizing conductors for pipe fill.

When we rarely had to go through a truss, we told the carpenter the situation, and he either 'boxed' out a section or showed us a better route.

Joists are one story, but I feel one should never, ever, drill a truss!

Unless designed otherwise, the truss frame construction supporting the floor of an attic are not designed to carry much of a load. I do not have my book here, but I will try to read it at work and let you know.


When running wire in an unfinished attic, lets not forget about 320.23, especially since drilling is not an option!
Pierre

[This message has been edited by PCBelarge (edited 10-25-2003).]

Pierre,since you brought up 320.23,I am always scrambling to comply with this one.
A lot of times the framers will put an attic acess in after I'm long gone. And it always seems to wind up where I presume to be the least likely place,and of course right next to several wire runs that would have been way out of the way otherwise.


Russell