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Old 09-15-2009, 02:25 AM   #1
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Cut a floor joist?


I am finishing a basement and to add a cold air return I would need to cut a floor joist. It would just be a small section of the bottom of the joist. Can this be done?

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Old 09-15-2009, 05:53 AM   #2
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Cut a floor joist?


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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Old 09-15-2009, 06:33 AM   #3
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Cut a floor joist?


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.

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Old 09-15-2009, 07:08 AM   #4
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Cut a floor joist?


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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Old 09-15-2009, 08:25 AM   #5
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Cut a floor joist?


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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Old 09-15-2009, 08:37 AM   #6
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Cut a floor joist?


Info on holes & notching

http://books.google.com/books?id=iwS...joists&f=false
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Old 09-15-2009, 09:12 AM   #7
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Cut a floor joist?


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-guida...ngofjoists.pdf
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Old 09-15-2009, 09:43 AM   #8
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Cut a floor joist?


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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Old 09-15-2009, 09:56 AM   #9
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Cut a floor joist?


What type is it? eg open chord type.
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Old 09-15-2009, 09:59 AM   #10
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Cut a floor joist?


It is a open floor truss with all the heat ducts and returns and electrical running through the truss.
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Old 09-15-2009, 10:02 AM   #11
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Cut a floor joist?


Here is a photo of the truss.
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Cut a floor joist?-floor_truss.jpg  
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Old 09-15-2009, 10:05 AM   #12
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Cut a floor joist?


*ouch* whole different story now....

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Old 09-15-2009, 10:07 AM   #13
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Cut a floor joist?


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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Old 09-15-2009, 10:09 AM   #14
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Cut a floor joist?


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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Old 09-15-2009, 10:31 AM   #15
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Cut a floor joist?


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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