# Maximum hole in floor joist



## Risch (Feb 12, 2008)

Hi. I need to re-route a 6" vent run through a 10" joist, and continue the run to an outside vent. I understand it can be done. I need to know what size hole through the joist would be best to maintain joist strength integrity' i.e.: a 6" hole with two 90 degree vent turns, or two 10"x3"x6" register boots? I appreciate any help and suggestions

Risch


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## rjordan392 (Apr 28, 2005)

A 6 inch hole in a 10 joist is too big. Don't do it. I believe the maximum allowed size is near 2-1/2 inch's. A carpenter should be along soon who will give the exact size on a 10 inch joist and other details.
You will have to run the duct under the joists.

I just found this on a search, go to:
http://tileyourworld.com/construction/JoistBoringGuide.pdf
Its everthing you need to know on boring and notching joists.


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## AtlanticWBConst. (May 12, 2006)

You'll have to come up with another route for that vent.

The previous link does a good job at explaining the "concept" of putting holes in joist, and maximum allowed bore size.


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## Joe Carola (Apr 14, 2006)

Risch said:


> Hi. I need to re-route a 6" vent run through a 10" joist, and continue the run to an outside vent. I understand it can be done. I need to know what size hole through the joist would be best to maintain joist strength integrity' i.e.: a 6" hole with two 90 degree vent turns, or two 10"x3"x6" register boots? I appreciate any help and suggestions
> 
> Risch


Who told you that you can cut a 6" hole in a 2x10?


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## jcalvin (Feb 6, 2008)

You can drill holes in joist no closer than 2 1/2 from the outside edge of the joist, but, the hole cannot be any larger than 1/3 the floor joist...3 1/3 inches at least in NC.


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