Remodeling our kitchen (and putting it on YouTube so want to make sure I'm right). I need to run 2 new circuits in our kitchen on a half wall so I can't run them down. Basement is open but the bottom plate of the half wall is resting on a beam that is supported by steel posts. Beam is 2 ply 2x10's.

Currently there is a wire going diagonally up through the beam into the half wall. I wanted to make sure that was to code before copying that twice. I have a permit and it will be inspected so want to make sure I won't be re-running this later.

Is drilling diagonally through a 2 ply beam acceptable?

I've tried googling but can't find people talking about it. All I could find was drilling through the side of a beam and don't drill straight down through the center.

Image 1: Current example of what I want to do if legal enter image description here

Image 2: The bay I would be doing it in. enter image description here

Image 3-4: Context shots of the beam, stairs, and joists it's holding enter image description here

enter image description here

  • 2
    Image of current wire is too large for this site. Will upload somewhere else and link That is a very common problem. I have some ideas to fix that (and will hopefully implement on Codidact, when I have time...). If you have Windows, I recommend downloading Paint.net load the picture and then save it as a JPG with lower resolution. Paint.net will show you the file size before you Save - ideally get the size < 1 Meg. Feb 7, 2021 at 19:42
  • Need more info: 1) what is above beam (rooms, storage, waterbed, etc.) 2) what is span of floor joists resting on beam on each side of beam, 3) what is distance between steel posts, 4) where are all drilled holes located along beam (distance from exact center of span of beam)???? Also, are there any posts (4x4 or larger) resting on beam?
    – Lee Sam
    Feb 7, 2021 at 21:32
  • 9ft of floor joists hung on beam with hangars. Those floor joists are carrying kitchen. Above the beam is a half wall that goes around our basement stairs. Beam has nothing on other side cause stairs. The holes would be drilled 2ft from a steel post supporting it. No posts resting above it. Just supporting joists where they had to be cut around stairs.
    – Dylan Buth
    Feb 7, 2021 at 21:54
  • Thanks for additional info. What is #3? Please clarify that stairs do not transfer any load to beam.
    – Lee Sam
    Feb 7, 2021 at 22:41
  • It would be on the other side of another post if so. I can't remember how I did it. The stringers are hung on a joist but I can't remember if that joist goes full length or not. I'll have to double check when I get home.
    – Dylan Buth
    Feb 7, 2021 at 23:01

1 Answer 1


I’ll try to answer anyway. I’ll make some assumptions and you tell me if I’m wrong.

The contributing load on the beam is 40 pounds per square foot (psf) Live Load plus 15 psf Dead Load for a total load of 55 psf.

If the joists on one side of the beam (and supported by the beam) spans 9’. So, half the 9’ floor load is transferred to the beam and the other half is transferred to the next support. Therefore, the floor load is :

55 psf x 9’ / 2 = 248 per linear foot along the beam, plus:

The weight of the wall above is about 15 psf x 4’ high = 60 plf

Therefore, the total weight on the beam is 248 plf + 60 plf = 308 plf

(I don’t think the stair connection contributes to the beam because it occurs at (or very near) a post. )

If the steel posts are 10’ - 12’ apart, there should be no problem drilling a diagonal hole within 3’ of the end of the beam. (Each 2x10 will support about 160 plf depending on the species and grade. 160 x 2 = 320 plf which is slight more than the required 308 plf.)

If the steel posts are 14’ apart, the allowable load goes down to about 120 plf, depending on the species and grade. (120 x 2 = 240 plf which is less than the required 308 plf.)

Holes not drilled in the middle third of the span are acceptable up to a certain size...and you are not approaching that size. (Btw, don’t drill multiple holes along the beam, especially in the middle third of the span.)

Note: make sure your refrigerator is not resting along this beam in any way.


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.