Floor Joist Notching Chart
These are general building requirements and you
should check with your local building department, engineers or others
before cutting or drilling any floor joist or roof rafters.
The holes in the center one third area of the floor joist can not be larger than one third of the floor joist size and need to be at least 2 inches from the edge.
For example: if you have a 2 x 12 floor joist that is 11 1/2 inches wide, one third of 11 1/2 inches a maximum hole of 3 3/4". This whole must be kept at least 2 inches away from the edge or the top and bottom of the floor joist.
No holes are you allowed to be drilled on either side of the floor joist and can only be drilled in the middle one third section.
You are allowed to notch the top of the floor joist at both ends of the one third sections, as shown in the illustration above. These notches can be no more than one quarter, of the width, of the floor joist.
For example: if you have a 2 x 12 floor joist that is 11 1/2 inches wide, one quarter of the width, would be a notch no bigger than 2 3/4 of an inch.
Do not notch the bottom of floor joist. Check with your building department before making any structural alterations to a building.