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We needed to replace the air conditioning evaporator coil and air handling element. In this house the cooling element is located inside the attic of the house. And up in the attic space is really tight. The house has 2x4 roof trusses, and those trusses are reinforced with an additional 2x4 attached to create a T-shaped cross section. I've never seen this type of construction before. See photos...

Attic Roof Truss

The reinforcement(2"x4" construction lumber) is attached as a T-Shape.

T-Shape

So why is that there? Is that a standard truss manufacturing technique? I'm guessing the addition is to prevent bowing (or failure in that mode...) My immediate problem is that with those elements there we are absolutely unable to snake the evaporator unit thru the trusses to even get them into the attic. There is not enough width between two adjacent trusses to push the unit through.

My tendency is to remove the top of the T on two adjacent truss elements and replace the top of the T-off center (think L shaped reinforcement...). As far as I can tell that will still perform the reinforcement function and allow for Heating Ventilation AirConditioning (HVAC) repair.

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Those are stiffeners, as you suspected. Large roof systems require stabilization of those long members. The truss plan provides schedules for the carpenters to follow in adding them on-site. It makes transport simpler.

I don't think it would jeopardize the integrity of the truss by shifting them flush to one side of the truss member, but you'd need an engineer to give you legal approval. Just be sure to nail them at least as often as they are now with 12d nails or better.

Of course, you could always remove them and replace them as they are now after repairs have been made.

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    +1 exactly. This type of stiffener is placed on “long” members that are in compression. The stiffener keeps the member from buckling in compression. Often the truss manufacturer will require a member to be placed perpendicular to the chord about halfway from top to bottom, but the brace is required to be connected to the end gable walls at both ends. If you remove it temporarily, make sure the chord is braced in the middle temporarily. – Lee Sam Mar 5 at 22:32

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