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I removed some in-wall ducting coming from the attic that fed registers on both sides of the wall. I intend on patching up the drywall of course, but before I do I want to block up the hole in the top plate as seen in the photos, and make sure that it is structurally sound. Studs are 16" on center.

Two questions:

  1. There is existing strapping for the top plate on both sides of the wall, it extends about six inches to either side of the hole in the top plate. Since I don’t know the quality of the fastener used to affix the strapping to the top plate and the condition of the strap itself, should I add additional strapping for structural purposes?
  2. Of the several locations that I removed this ducting, most don’t have enough top plate exposed between studs to affix blocking to, so it would have to be stud-to-stud, or on top in the attic, but even there the ceiling joists don’t provide much room to connect blocking to. Any recommendations for blocking the hole in the top plate?

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3 Answers 3

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The home was presumably built to be sound with the duct in place, so it's still sound with it gone. You don't have to build it better.

Just add blocking as needed to support the drywall. If you happen to have clearance to lay a plate through the entire area and screw it in, great. If not, don't sweat it.

One strategy is to add short legs to a plate before you put it in place, then screw the legs to the adjacent studs. You don't really need to double it, and you can position it at an arbitrary height that makes sense as drywall backing.

ELEVATION (FRONT) VIEW
______                           ________
______|_ _____________________ _|________
______| |_____________________| |________
    | | |                     | | |
    | | |<-- screws --------->| | |
    | | |                     | | |
    | | |                     | | |
    | |_|                     |_| |
    | |                         | |
    | |                         | |
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  • I was typing adding legs and then nail plates on top from attic but your answer is better, avoids working in attic.
    – JACK
    Apr 19, 2022 at 18:20
  • Thanks for the excellent suggestion. The strategy for blocking seems so logical, I guess my brain just doesn't work quite like that yet. Much appreciated. When it comes to the structure, I guess what made me question the tie strap adequacy was the fact that our rafters are undersized (2x4s) etc, so that put into question the engineering (or lack thereof) for the rest of the house.
    – Matt
    Apr 19, 2022 at 20:29
  • What makes you say they're undersized? Modern engineered trusses are commonly built entirely with 2x4 even in my snowy climate.
    – isherwood
    Apr 19, 2022 at 20:39
  • It's a stick-built roof, no trusses. House was built in 1961.
    – Matt
    Apr 19, 2022 at 20:41
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    It's made it 60+ years, I would assume it's sufficient.
    – spuck
    Apr 19, 2022 at 20:53
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There's an even easier solution here if you have a power screwdriver of some sort (better still an impact driver): pocket the screws. Cut your 2x4 to length and screw it into the surrounding top plates.

To put it another way, you take some 3" deck screws and drive them into your 2x4 at an angle about 1" from the ends. This avoids the need for any cleating (like isherwood suggested). I don't see any metal to get in your way.

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  • Easy enough. Thanks for the suggestion!
    – Matt
    Apr 20, 2022 at 21:51
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The Building Code requires a lap at top plates of 16” and nailing of two 16d common, or three 3”x0.13” nails, or three 3”x14 gauge staples. (See Table 2304.9.1, item 13.)

This might be easier to install.

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  • 2
    If I'm following you, in an ideal world I'd prefer to do this. However, the ceiling joists are in the way of attaching anything to the top, so any repair would require cutting out the top board of the double top plate and temporarily supporting the ceiling joists. Does that clarify things or am I way in the weeds?
    – Matt
    Apr 19, 2022 at 20:52

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