I'm in the process of installing central vac lines (2" OD) in a finished house, and I am trying to run a line into the upstairs hallway. I have removed drywall in the garage below and drilled a hole down using an installer's bit, and found the hallway wall is sitting directly over top of a joist.

Entry point and hopefully future location of inlet Looking down inside wall, drill bit visible Looking up at drill bit and joist from garage

This is an ideal location as it is the only spot that allows me to reach every upstairs room. Any further and I have to open up walls on inside spaces, which I want to avoid.

There's a not-as-ideal alternative on a nearby adjacent wall (about 3' away) that would allow me to come down between joists, but the hose only reaches halfway into one of the bathrooms, so I'd prefer the original location if possible.

Is there a safe way to make this work? The challenge is that I will have to drill through a bit more of the joist to fit the 2" pipe in (as I already inadvertently did..).

Couple more images:

Looking up at garage ceiling Full enter image description here Full

EDIT 2013-05-07:

I drilled a second pilot hole right at the edge of the bottom plate, and decided I had enough room to come in on an angle with a 2" hole saw. The "notch" on the 2x8 isn't any deeper than 1/4", you can actually still see the original pilot hole where I came through the joist (the groove nearest the camera). I'll need to use some flex pipe to hook this up because of the angle, but that is no big deal.

2" hole through bottom plate

Do I still need to sister another 2x8 to this? How significantly is this really affecting the strength of the joist?

EDIT 2013-05-10

Got it done, using 2" ID flex pipe (typically used to hook up those under-cabinet vacuum sweep inlets). Thanks everyone.

enter image description here enter image description here

final connection done

  • You can notch out enough of the top to put a 90 in without structural issues. Are you able to do this or does it have to be a straight line down?
    – DMoore
    May 6, 2013 at 3:32
  • 3
    A 2" notch on that size joist seems questionable...but I'll defer to the experts.
    – DA01
    May 6, 2013 at 6:46
  • What's on the other side of that wall? Closet? Room? Hall?
    – longneck
    May 6, 2013 at 20:36
  • nice. i would not.
    – mike
    May 8, 2013 at 5:10
  • Very nice. I knew it would make it. No bracing needed.
    – DMoore
    May 9, 2013 at 4:49

4 Answers 4


My answer is to cut your two inch hole as close to your drywall as possible. In the picture you went right down the middle and barely hit the joist. Methinks that you could drill right along the side and have to barely notch out the joist below. Might not even have to notch all the way through it. No reason for vac lines to have to be centered in your wall. Use the notch guidelines I found to help further.

  • Notches in floor joists may occur in the top or bottom of the member but may not be located in the middle third of the span.
  • A notch may not exceed one-sixth of the depth of the joist except at the very end where it may be one-fourth of the joist depth.
  • The length of joist notches cannot exceed one-third of the depth of the member.
  • Holes bored in joists must not be larger than one-third the depth of the joists.
  • Holes cannot be located within two inches of the top or bottom edge of the member, or to any other hole located in the member.
  • Holes cannot be located within 2" of any notch.

Below is a helpful chart that provides actual notch and hole size limitations for 2x4, 2x6, 2x8, 2x10 and 2x12 joists. It should be noted that limitations on the allowable notching and boring of wood joist are meant to retain the structural and functional integrity of the member.

enter image description here

  • An alternative is to call your city's permit department, tell them your joist size and tell them the notch size you want to cut, and see if it passes local code.
    – DMoore
    May 6, 2013 at 15:22
  • 2
    I doubt that a notch is suitable without additional reinforcement. Assuming that's a 2x8 or 2x10 joist, cutting a large enough notch to get a 2" elbow fitting in there is going to be way more than 1/6 the depth. Plus from the pictures it looks like it's in the middle of the span anyway.
    – Hank
    May 6, 2013 at 16:12
  • Nothing wrong with adding supports for the notch too. The pipe will go out one side. Can brace the other side.
    – DMoore
    May 6, 2013 at 16:31
  • Henry's point is well taken. The table indicates the notch most likely would be egregious. The brace would need to be substantial to meet code - might as well sister on a joist and make the rest of the task quiet easy., certainly less futzy.
    – mike
    May 6, 2013 at 18:36
  • The fact is that the pipe should not go right down the middle of the joist - meaning sticking out on both side. He might be OK. It will be close. If not it is easy to brace or sister one side.
    – DMoore
    May 6, 2013 at 21:17

EDIT 2013-05-06 Afternoon:
Great new photo taken in the garage showing the joist layout.

In a nutshell, there is really nothing to worry about ... provided ...

A) the obstructing joist is not carrying a huge amount of weight from say a waterbed or massive safe

B) the joist is not carrying a huge amount of cantilevered weight (out to the left in the photo).

So ...

Given the new picture showing it is approximately a 4ft span, it'll be really easy.

I'd ...

1) Cut out a 12" or so section of the obstructing joist.

2) Use a large pair of vise-grips to pull any newly exposed nails through the subflooring.

3) Drill the 2-1/4" or 2-1/2" hole through the subfloor and the bottom plate of the hallway wall.

4) Install the vacuum pipe and fittings and wall receptacle at this point, before sistering on a new joist.

5) Cut a new two-by joist about 48" long to reach from the lap-joint near the I-beam to the wall support. It should cut long enough to loosely butt at the lap joint and also sit on top of the double top-plate of the wall for 2"-6".

6) Use a skillsaw free-hand to rip about 1/2" off the width of this new joist. For example, if its a 2x8, rip it from being 7-1/2" wide to 7" or 6-3/4" wide. This will make installation quite a bit easier.

7) Dry fit the new joist. Trim some if necessary so as to make it easy to maneuver the joist into place.

8) If the vacuum pipe is keeping the new joist from laying flat against the obstructing joist, you can cut some lengths of 1x2" or 3/4" plywood to place in between the two joists.

9) Optionally apply some construction adhesive (I would not)

10) Use 2-1/2" or 2-3/4" sheet rock screws to secure the new and old joists.

END OF EDIT 2013-05-06 Afternoon

EDIT 2013-05-06 Morning: Good to know they are indeed parallel. As a work around, perhaps the mfr/vendor sells a flexible coupling for situations like this, or perhaps a length of 2" ID thick-walled vinyl hose would work, or a length cut from a shop-vac hose of fortuitous diameter. In any case, it would involve cutting an oval passage through the subfloor and the hallway wall's bottom plate by cutting two 'overlapping' holes, perhaps 1-1/2" dia, and 'cleaning up the sides of the oval with a sawzall or keyhole saw or chisel.

This flex-splice approach may or may not be feasible. Being a work-around, like the notch+elbow method, there is a good chance that something unforeseen will come up that will prevent completion ... so I still favor a direct approach, such as sister+section or sister+chisel described below.

If you do choose the notch+elbow method, I'd suggest a 45 rather than a 90. Also, when laying out the location of the hole, I'd take into account the OD of the female ends of any nearby fittings such as the elbow to the wall receptacle. With the notch+elbow approach you might encounter nails under the bottom plate that were used to nail the subfloor onto the top of the floor joists.

Regardless of approach, I'd reach into the cavity of the hallway wall with a putty knife to probe between the drywall and the bottom plate to check for drywall screws that the hole-saw would encounter.

Looking forward to additional photos.

END OF EDIT 2013-05-06 Morning

If the hallway wall is indeed running parallel to the floor joists, then I'm surprised that the joist underneath the hallway way is not doubled up. But then maybe the hallway wall is just a few feet long, or maybe it's actually an extra joist. I first would confirm the orientation by drilling a second pilot hole.

Assuming they are parallel, my inclination would be to first add an auxiliary joist on the non-problematic side, then use a sawzall with a long blade to cut out a complete section of obstructing joist (say 8" wide) to make room for the 2" OD pipe. Some additional wide angle photos would help give a sense if this would be a feasible solution. If it is feasible, then depending on various aspects, I might cut out the 8" section first because it would be easier. Another approach would be add the auxiliary joist, then drill the pipe hole from above from inside the hallway wall through the hallway wall's bottom plate, then on a step ladder in the garage, use a sharp 1-1/2" to 2" wide chisel to chisel out an adequate trough down the face of the obstructing joist.

The process of adding an auxiliary joist (which, by the way, does not need to run the full length of the existing joist) is called sistering. With a skill saw, cut new two-by to length, then rip about 1/2" off it's width over the full length. Dry-fit the auxiliary joist, apply construction adhesive, clamp in place, screw together with 3-1/2" sheet rock or deck screws, pre-drilling on the insertion side so that the screws will draw together the 2 two-bys. The 2 two-bys will total about 3" in thickness. Use 3-1/2" screws and angle them for a superior and clean looking job. If you are really good with a hammer, you could clamp and nail the two joists together with 16d bright common, but I'd use 16d galvy commons for their extra grip. A pneumatic nail gun won't draw together the 2 two-bys.

If I was working alone, I'd screw or nail a couple lengths of one-by on the bottom side of the joists and perpendicular to the joists to hold the auxiliary joist in place once I lifted it up into place and applied the clamps. I'd let the one-bys protrude about 3" beyond the obstructing joist into the bay that is going to receive the auxiliary joist. I'd use three clamps, one on either end to hold the joist in place, and one to keep close to where I was screwing.

I'd be happy to go into more details. If I understand it correctly, the joist-photo is taken from inside your garage, looking up at the floor joists. If you could take and post a couple more photos, it would be helpful, in particular:

1) A wide-angle photo shot from the level of the garage floor looking directly up at the proposed location. This one should show as much of the joist layout as possible.

2) Photos of the 'other side' of the obstructing joist that show any potential issues with sistering an auxiliary joist on that side.

3) Photos that show how the obstructing joist is supported.

It would also be helpful to know the length and width of the obstructing joist.

  • I'm quite sure it's parallel, and that I've drawn the joist location correctly. The joists are supported on steel I-beams at both ends. I think the joist isn't doubled because this is a non-load bearing wall and it just happened to work out in this spot. My house is a bit strange because everything is offset: the edge of the garage is below the middle of the upstairs hallway, and there is 20% of another bedroom above the garage. This is not a great pic but I happen to have it available: i.imgur.com/9QDKVkI.jpg. I'll edit the post with a better one when I get home.
    – gregmac
    May 6, 2013 at 15:59
  • Also minor note, I will have to drill the 2" hole from the bottom, as I don't have a way to get a hole saw in the wall and drill down (nor do I have high hopes that would work well anyway -- a flex bit would be needed, which puts pressure on the drill bit, and hole saws tend to bind if you don't hold them straight).
    – gregmac
    May 6, 2013 at 16:03
  • Better pictures added to OP
    – gregmac
    May 7, 2013 at 0:38

Do you have unobstructed access all the way to the supports at the end of the adjacent joist bays? If so, you could slide in 2 new full-length joists. You might have to open up the ceiling at the other end to install joist hangers.

With 2 new joists in place you could notch your existing joist as big as you need.

Overkill, I realize. But sometimes overkill is the simplest solution.

  • Nope, ~half the joist goes beyond the back of the garage and is over finished ceiling, hanging on a header joist which I assume is sitting on top of another I-beam.
    – gregmac
    May 7, 2013 at 0:39
  • what I meant by unobstructed was no horizontal wires or plumbing through the joists farther back. if not, you might be able to insertr a new joist by turning it 90 degrees so it lays flat, slide it in and turn it upright.
    – longneck
    May 7, 2013 at 3:10

In you picture of the drywall, there appears to be a door to the left. What's on the other side of that wall? Is is a closet? Cut a hole through the wall in to the closet and run you vac line down through the floor. Build a plywood or drywall box around it.

  • Actually that is definitely an option, though I'd prefer to keep it in the walls if possible.
    – gregmac
    May 7, 2013 at 0:39

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