# Cut a floor joist?



## Just Bill (Dec 21, 2008)

You are allowed to cut some, but how much depends on local code. Most floor joists are 2x10 or larger. Is there room to reinforce that section with a 2x6-2x8??


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## DangerMouse (Jul 17, 2008)

i just had this question yesterday. i called my architech/engineer friend and he said for the 2x12 i have, i can take off 2" is all.
he also recommended using a sabre saw and making an arch rather than straight cuts.

DM


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## Scuba_Dave (Jan 16, 2009)

How small is small?
How big is the floor joist ?
Where will the cut be located on the joist......
....1st third of the joist, middle 3rd of the joist, or the end 3rd ?


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## stuart45 (Jun 20, 2009)

Our Building Regs state that notches can only be taken out of the top edge of the joist, and then only in the permitted zones. Holes must be in the neutral axis or centre line. Your Regs however could be different to ours, but I would think that cutting at the bottom is more likely to weaken the joist, rather than at the top.


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## Scuba_Dave (Jan 16, 2009)

Info on holes & notching

http://books.google.com/books?id=iw...um=3#v=onepage&q=cutting floor joists&f=false


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## stuart45 (Jun 20, 2009)

Interesting that you are allowed cuts in the bottom, but it looks like an arched cut is recommended.
These are ours.
http://www.eastdevon.gov.uk/bc-guidancenote7-notchingofjoists.pdf


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## RAYCC3 (Sep 14, 2009)

Sorry for not posting this orignally, however my floor joists are actually a truss style joist and not the typical 2x8 or 2x10 sold joists. So what I would like to do is cut into the bottom of the floor "truss" for a cold air return. Can I do this?


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## stuart45 (Jun 20, 2009)

What type is it? eg open chord type.


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## RAYCC3 (Sep 14, 2009)

It is a open floor truss with all the heat ducts and returns and electrical running through the truss.


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## RAYCC3 (Sep 14, 2009)

Here is a photo of the truss.


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## DangerMouse (Jul 17, 2008)

*ouch* whole different story now....

DM


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## stuart45 (Jun 20, 2009)

I am not a Structural Engineer, but my guess is that its not normally advisable to cut the bottom of this kind of joist, although there may be a way of adding some strength to it. Is there no other way of doing the job without cutting it?


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## RAYCC3 (Sep 14, 2009)

Well I can't see it being an issue to drill into and cut the bottom section of this truss..... It will not lose support as the basement wall is also supporting the truss. I have a cold air return problem and the only wall I can install the return on would be the wall with the truss. Right now I have the cold air return in a closet because I didn't want to drill/cut into the floor truss and I guess that is a code violation so I need to move it. Any suggestions would be greatly apprciated.


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## Aggie67 (Dec 20, 2008)

I am a structural engineer, and I can say it is NOT advisable to cut into the bottom or top cords of a wood truss, or any of the webbing, without speaking first to the truss manufacturer. Those look like engineered trusses, and you can do some seriously bad things to a structure when you cut into them. 

The phone call is free. Just call them and get their recommended reinforcement scheme (that is if they'll allow it).

Also, how much of a cut are you talking about?


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## RAYCC3 (Sep 14, 2009)

Aggie thanks for the advice! Just enough of a cut for a cold air return so no more than 10-12 in length and 3 inches of the 3 1/2 in 2 x4 on the bottom. So it would be a cut out of this bottom 2x4 of that size. Does that change anything since I am not cutting it completely out?


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## Aggie67 (Dec 20, 2008)

That sounds like you're only leaving 1/2" of material behind after the cut. To an engineer, that 1/2" doesn't even exist.

Call the truss maker. They'll be in the best position to help you out. I've dealt with a bunch of them in my practice, and they have engineers on staff to support their products and field mods. The manufacturer's stamp will be on the top and bottom cords. It also looks like a new structure, so the plans will more than likely be on file somewhere down at the building department.


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## Thurman (Feb 9, 2009)

I agree with aggie, I would not cut the engineered truss at all. They are engineered with some parts of the truss in suspension and some parts in tension, therefore: if you cut anything you change the way the truss was engineered. After seeing the picture I would recommend having a sheet metal shop design, and fabricate for you a "transition" piece which would go between one of the trangular shaped areas. Whether you are currently using square, rectangular, or round duct, this transition piece can be made to fit either one, and you can continue your run. Good Luck, David


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## RAYCC3 (Sep 14, 2009)

Thanks for your help Thurman! The problem is that the current basement wall sits directly below the bottom of the truss and in order to run a retrun down the wall to the basement floor is to go through the truss. The option that I have is to frame a box off the wall that sits on the truss and put the return in there. I don't want to have to do that since it will look awful.


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## stubits (Dec 30, 2008)

I don't know you're particular home, but I am certain it won't look awful. This is done all the time. My house has a couple of chases and they are what they are. Most of all, I'd rather have a stable and secure home with an HVAC chase than a perfectly run duct in a house where the stability and structure has been sacrificed.


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