I am planning to run CAT6 from the basement to the attic through the first and second floor of my 1905 wood house (renovated some time in the last 20-30 years). Location is Seattle.

There's an existing structured media cutout on the second floor used for CAT3 phone that runs into the attic and off to various spots that I plan to hijack and use to pull new stuff once I get all the lines into the attic from the basement. Assuming they aren't stapled down. 😬

The CAT3 comes into the house from the left exterior wall and (probably) runs up the wall into the attic and down into the cutout.

Aside from exterior walls, the only wall that is shared by all levels is the interior stairwell. My plan is to build out a cabinet under the basement stairs.

My question: what sort of structure will I find in the stair walls for this era of house (as best as one can reasonably predict)? I'm trying to understand what I have to drill through and what I will have to avoid.

Floor plans are mostly to scale, still a work in progress.

The first floor wall seems to be cantilevered on the basement wall (first sits offset left of basement by 4-5 inches).


First floor

Second floor

Second floor

Basement wall

Basement wall

Basement area

First floor wall

First floor wall

Second floor stair well

Second floor wall

  • 1
    A 1905 house would be balloon framed, usually real easy to pull wires through. This remodel looks rather extensive, which would complicate the openness of the balloon framing once had. Since renovations that are major require the whole structure be brought up to the code requirements during that time. Which means fire blocking in all the open stud cavities exposed during the remodel
    – Jack
    May 31, 2020 at 5:42
  • @Jack Did a bit of research on the area and history and this is likely. Thank you for suggesting that. Going to investigate this a bit further from the attic. I suspect that some walls did get fire blocks because they were resheathed with drywall, but some where not and continue to be the old plaster.
    – Steve
    May 31, 2020 at 17:42
  • 1
    If I were committed to running these wires, I would start by cutting holes about 8" wide by 12" tall between each stud bay that lines up floor to floor. Each hole needs to be above the baseboard and below the ceiling about 12" so repairs to the drywall can be made easily. With a light, the holes can be drilled in the plates, being careful how the drill bit goes through the plates. There is no way to know where wire and pipes are. The smaller the hole the better to minimize contact with hidden things.
    – Jack
    May 31, 2020 at 19:10
  • 1
    The attic may not reveal anything that you could use. If the pull box is where you are planning to get to anyway, that conduit will or may get you the rest of the way.
    – Jack
    May 31, 2020 at 19:12
  • Thanks @Jack. There appears to be a straight shot on the left corner of the front wall. Doesn't look like any existing wiring or pipes in that stud bay. There doesn't appear to be blocking on the second floor wall (makes sense, still old plaster there), still have to check 1st and basement. It's also right above a closet in the basement, so that looks like a good spot.
    – Steve
    Jun 1, 2020 at 15:44

1 Answer 1


It should be a doubled-up (floor joist) header hanging between a doubled-up trimmer and a doubled-up stair header. "1905" - well, it's definitely not an engineered joist. (No light above the sink; that doesn't meet code ;)


It sounds like you're trying to do this Can I drill vertically through this from the main floor to the upstairs?

"It will not affect it structurally [citation needed] . If we go by the 1/3 rule, that's .45 inch. So not even a half inch hole is ok. In my 30+ years of experience, I've never put more than a 1/4" hole through a 1.5" member."

"Any more than that and you've substantially compromised it. A 3/4" hole is effectively half of a member. Common sense should tell you that that's ABSOLUTELY NOT OKAY."

"Just don't go cutting it, OK?"

But what you do need to do is cut open the walls and stop asking moot questions until that's done. But if you wanted me to run some Cat5, the last place I'd be doing it is where I'd have to violate the structural integrity of a staircase and its opening.

As seen in the linked picture, you cut holes like that above and below every penetration you plan to make, so that you can get a drill in there, and make them where they should (or shouldn't) be, and feed the wire. If that's 'not where they should be', you get to destroy more drywall, which when running utilities, is the enemy.

I can't look at a picture of drywall and tell you what to do, nor answer this specific question w/o the actual blueprints, nor would I trust them anyway. Verify in field.

  • It's like you chose the location because it's easier to stand on a stair case, than on a ladder, having moved furniture to get to walls where it should be, because you'd also have to go up and down that ladder a bunch of times and the staircase anyway. Running wire is a lot of back and forth. A lot of making holes. And a lot of patching holes, some of which are going to be, 'oops, nope; not here'.
    – Mazura
    May 31, 2020 at 1:12
  • "That's the drywaller's problem." (which is usually also me ;\
    – Mazura
    May 31, 2020 at 1:16
  • Thanks, I think that pretty much answers it. I will find another route. For me it wasn't about easiness or laziness, but about reducing the number holes drilled blindly and cuts into surrounding drywall and plaster.
    – Steve
    May 31, 2020 at 15:26

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