How do you sister a 2x4?

A homeowner, not me, cut two or three rafter cords to install a pull down stair set perpendicular to the rafter cord runs. Outrageous choice, as there was a whole huge garage ceiling, but now it should be fixed. Two or three cords were cut.

Precisely how should I sister on the new 2x4s? I’m thinking that the cutout section was about 24", so I need two feet for the hole, plus two more feet on each end. For fasteners, I’m thinking 10d or 12d nails, about four on each side, for a total of eight per 2x4?

Any comments are appreciated.

Pictures would help. But in the absence this is what I would do.
Treat the opening as you would a window and rough frame 2X4 around the opening. Install a hanger and nail the hanger to the newly installed 2X4. Thats it. 16d common nails would work and use hanger nails for the hangers.
The existing bottom cord would be resting in the hanger. Don’t forget to hanger the 2X4s that you installed for the rough opening.
This is probably clear as mud :slight_smile:

The problem is that it is not OK to cut a chord of a W truss for pull down stairs. I simply want to replace the cut out section, eliminating the pull down stairs. I agree 16d nails would work, though I still think that the right 10d or 12d hand nailers can be “just right” for sistering 2x4s.

The “window opening” technique would work to allow an opening, but that would require doubling the 2x4 along the entire cord, which is maybe 26 feet.

Your’re going to have to ‘head’ off the cutout sections with a doubled 2x4. Then you box in the opening if it isn’t already.
THen, you’re going to use truss splices to add some truss braces/triangles to re-stiffen the frame. I’d even jack up the opening to unload the spot and restress it upward. Then, the lowest it would sag would be level.
I left out afew details by not having specifics, but it should be straght forward.

At a cost of $300, I hired a structural engineer to comment on this case where two rafters are cut. He came up with two designs, one leaving the stair unit in place, another eliminating it.

The elimination plan, my original question, was as thought, plus a little bulkier. He wanted one 2x4 sistered on each side of the missing section, extending two feet on each side. In this case, that is six foot 2x4s. For fasteners, he wanted 12d nails 3" on center, twice what I thought.

Thanks to you here for suggesting the stairs be retained. However, his design is different from building a window opening header/jack type of frame. In a wall, the basic force is gravity compressing eberything straight down. Trusses are different, and have both compression and tension forces. I’ll explain in detail.

In summary, he wants a 2x8 tucked under the peak, running along the ridge, and two 2x8s running the same direction, attached to the nearest braces of the W truss just above the base cord. He wants Simpson connectors, not calling out specific models. I interpret to essentially be hurricane ties, h2.5 at the peak, h4 at the base.

The new member at the peak essentially keeps the peak from falling. Rafters are under compression, to my understanding.

The new members near the base look to help the walls from spreading, as the base cord is under tension. There is also some downward force on them, given the nature of thw W aspect.

At any rate, I appreciate the comments here and do not regret having this fellow look at the job.