# Cutting through top plate in load bearing wall



## venator260 (Apr 1, 2013)

I need to add returns to my HVAC system on my second floor as I'm pretty sure the A.C. would work better. In addition, there's no way that the system isn't starved for air, as there's currently only 2 smaller returns on the first floor. 

My current idea is to run up through a load bearing wall (as there's a 4 inch non-insulated cavity there, the other walls are either exterior or build with a 2x4 with the 4in. facing the drywall, leaving only a 2in cavity) and into the attic and then through the ceiling of the three upstairs bedrooms before covering all of the ductwork with insulation. 

Doing so, however, would involve cutting through the top plate of the load bearing wall in the center of the house. Is this something that can be done without compromising the structure of the house?


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## mattlreese (May 7, 2014)

How big of a hole would you make? 

Someone else can clarify better but you can do up to four inches without much of an issue, anything larger and you might need to build a bulkhead.


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## venator260 (Apr 1, 2013)

I was planning on running 3 4 inch ducts up through the hole so that I could run a return to each upstairs room. Since this is a 2x4 inch wall (true 2x4's, old house). So this would completely sever the top place and make a ~12 inch hole.


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## Nailbags (Feb 1, 2012)

The whole can not excced the maxium of 60% of the with of the stud 2-1/8" for a 2x4 and 3-1/4" max in a 2x6 hope that helps you under stand what you can do


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## venator260 (Apr 1, 2013)

Nailbags, that does help. My idea would have been to cut through it completely, as I wasn't sure if the top plate had any strain placed upon it after the walls and floors were completely assembled. Is there any way to brace it to leave a ~ 4x12 hole.


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## windowguy (Jan 27, 2009)

here's what he's trying to do because i did the exact same thing on my cape cod to get a return to the second floor. Imagine 3 supporting walls of a cape cod house. 2 exterior walls and one load bearing wall in the middle for support. Imagine running a duct from the basement through the 1st floor middle support 2X4 cavity space. to get to the second floor he needs to penetrate the cavity top plate. Its a complete cut through. Essentially he is severing the "lateral" top plate. So he is asking if severing a top plate compromises the "side-to-side" shifting support. The quick and dirty response would probably be its a bad idea, but he's curious if all the other framing of the entire house would compensate for a top plate being cut. 

I did it on my cap cod, i put some steel straps screwed on either side of the void to try to provide some connnection back, but looking back the screws i used were totally sub standard. I havent had to test it through a hurricane only because three years later i just wound up doing a complete add-a-level anyway..


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## Nailbags (Feb 1, 2012)

I understand what he wants to do. Best thing to do is to check with his building dept give a hypothetical Sanrio and see what they say they may say no problem.


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## carpdad (Oct 11, 2010)

In theory it looks like bad thing to do, but it is done often, especially when plumbing needs to go. Strapping will replace the cut wood, but don't just use plumber's strapping because it is too thin.
Mid wall in a house does not do anything for high wind/quake resistance, unless specifically designed, I suppose. Mid wall is sheetrock only and I have never seen cross braced mid wall around NJ, at least.
Joists and floor underlayment add to the strength of the house - they are nailed and locked together.


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## carpdad (Oct 11, 2010)

Sorry, but had another thought. There are other ways to let the pressurized air out of a room. One would be return register open to hall, and another may be to duct the returns in attic to more convenient/less destructive location from attic to the furnace.


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## venator260 (Apr 1, 2013)

carpdad said:


> Sorry, but had another thought. There are other ways to let the pressurized air out of a room. One would be return register open to hall, and another may be to duct the returns in attic to more convenient/less destructive location from attic to the furnace.


This is the easiest solution that I can think of, and I've puzzled over this for a year and a half.The exterior walls and this load bearing wall are the only two that have more than a 2 inch cavity in them. Any non load bearing wall was made with 2x4's with the 4 inch face facing the drywall. 

I discounted the exterior walls because of two reasons. They're full of blown in insulation. Getting a duct through would require cutting large holes in my walls. The walls have a texture that my wife and I like (and one that is original to the house from what I can tell) and one that I would not be able to replicate. Perhaps I could get a plastering company to replicate it; but that's not in the financial cards, especially after I learned that I may need a new roof. 

Since cutting through the top plate doesn't seem to be a safe option, I may run a duct up to the second floor through this wall and place the returns in this wall without going into the attic. I should be able to get two up through in this way. I wanted to go with the into the attic plan because I would be able to run 3 ducts into one stud bay (not sure if that's the correct term). if I don't go into the attic, I'll have to put one duct per stud bay. This would also leave one room without a return. 

I'm planning this for both added return to the furnace and to hopefully allow my central air to work better by pulling the hot air into the system that has risen upstairs.


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## jogr (Jul 24, 2007)

All you are doing is separating 1 load bearing wall into 2 load bearing walls separated by 12 inches. As long as the floor joists above are properly supported on the two load bearing walls you are fine.


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