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#153613 - 10/22/03 04:58 PM Trusses
Ryan_J Offline

Registered: 08/19/03
Posts: 1355
Loc: West Jordan, Utah, USA
What are we allowed to do to a truss, as far as drilling, cutting, notching, altering, etc...

Ryan Jackson,
Salt Lake City

Building Codes & Related References
#153614 - 10/22/03 06:46 PM Re: Trusses
ga.sparky56 Offline

Registered: 11/24/02
Posts: 582
Loc: young harris georgia usa
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.


#153615 - 10/22/03 09:41 PM Re: Trusses
Big Jim Offline

Registered: 07/18/03
Posts: 377
Loc: Denver, CO USA
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.

#153616 - 10/23/03 02:06 AM Re: Trusses
iwire Offline

Registered: 01/05/03
Posts: 4343
Loc: North Attleboro, MA USA
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).]
Bob Badger
Construction & Maintenance Electrician

#153617 - 10/23/03 01:38 PM Re: Trusses
Bill Addiss Offline

Registered: 10/07/00
Posts: 4196
Loc: NY, USA
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?


#153618 - 10/23/03 01:42 PM Re: Trusses
pwood Offline

Registered: 02/04/03
Posts: 64
Loc: castella,calif usa
all excellent answers .it is amazing what forms of truss butchery an inspector sees during framing 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!

#153619 - 10/23/03 01:59 PM Re: Trusses
Bill Addiss Offline

Registered: 10/07/00
Posts: 4196
Loc: NY, USA

Slightly off-topic, but here's some past discussion on Engineered Beams:


#153620 - 10/24/03 06:42 PM Re: Trusses
Pinemarten Offline

Registered: 08/23/03
Posts: 122
Loc: Edmonton, AB, Canada
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!

#153621 - 10/24/03 09:00 PM Re: Trusses
PCBelarge Offline

Registered: 06/08/03
Posts: 657
Loc: Dobbs Ferry, NY, USA
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!

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

#153622 - 10/24/03 09:22 PM Re: Trusses
ga.sparky56 Offline

Registered: 11/24/02
Posts: 582
Loc: young harris georgia usa
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.


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