I have a new home I just moved in to and rather than having them put this stuff in ahead of time (silly me) I'm now trying to do it now.

Here is my situation... I live in a 2 story home with a finished basement. One portion of the basement is unfinished.

I'm wanting to run some future-proof low-voltage conduit from attic to basement (unfinished area) where I have a Structured Media Enclosure mounted.

The only straight shot from attic to basement (that I can see) is the cold air return which has an grate on each floor in roughly the same place.

My question is... given "common" building practices... Could I theorhetically fish a straight pvc pipe along one side (exterior) of the cold air return all the way to the utility room in the basement?

Here are some bad photos taken from a bad video that I took while the home was in pre-drywall phases...

gaps around cold air return on 2nd floor wide shot of cold air return on 2nd floor with a gap to the left

UPDATE 1/30/2013
I feel as if this space is no longer feasible for the "future-proofing" conduit runs I've been envisioning. I've decided to go a different route using an interior wall on the main floor that's ceiling bumps into a WIC in the 2nd floor. Depending on the place it pops up in, I'm going to run 4-5 smaller PVC conduits within that wall, and up to the WIC, then up to the attic. This should give me precisely what I'm looking for in regards to future-proofing.

Also, attached are some pictures of a very closely built home to mine in pre-drywall stages that I am now using as a guide to determine where walls meet and which ones I MAY be able to use to run this type of conduit.

  • The biggest "code" type issue you'll run into, is spread of fire between floors.
    – Tester101
    Jan 29, 2013 at 16:23
  • I guess my biggest concern is, do you think there is commonly enough space to do what i'm wanting to do? Is there usually obstructions in that little gap? Jan 29, 2013 at 16:32
  • 1
    Around the duct should be fire stopped between floors...
    – Steven
    Jan 30, 2013 at 1:59
  • @Steven That sounds like the answer to me. "No, the area around the duct should contain fireblocking between floors." IRC 2012 R302.11(4).
    – Tester101
    Jan 30, 2013 at 14:33
  • And don't forget to seal both ends of the conduit with fire stop caulk, which is available at your local home center.
    – longneck
    Jan 30, 2013 at 15:07

2 Answers 2


I take it you're hoping to poke sticks of conduit up from the basement and hope to come out in the attic without hitting anything? It could happen, but I'd be rather surprised. 1.5" conduit is fairly chunky, I think you're likely to hit something. If you wanted to fish a few runs of Cat 6 I'd say your chances were good. But conduit? (BTW, bonus points for knowing better than trying to run inside the duct.)

Even if there's obstructions, it may be possible to make the run by cutting discrete access holes to cut out the obstructions, assuming they are non-structural. If you haven't yet done so, examine each floor carefully to determine if there's enough space to even make the run. Measure carefully to arrive at accurate void dimensions, and ensure the proposed run aligns on each floor, which may not be that simple. Once you've determined it's feasible, start pushing pipe, keeping track how much length is pushed up. You'll likely hit something. Figure out where it is vertically. Gain access and clear the obstruction. Repeat as necessary until the attic is reached. Good Luck!

  • Thank you! I've determined that the gap in the air ventilation is no longer feasible in my eyes for what I'd love to accomplish. I've done this by viewing an identically built house on a different street that is still in pre-drywall stages. I've taken pictures of all of it for future reference to help aid a different location. I'm not sure whether I should try posting my new location as an update to this question just for clarification of what ended up working or not. Jan 30, 2013 at 13:06
  • Joshua- Yea- Please update your original post (OP) with an edit and tell us what you did. I am curious to how you are going to solve that problem and why you changed your mind from running next to the vent? bcworkz Nice answer.+1
    – Piotr Kula
    Jan 30, 2013 at 13:45

No, the area around the duct should contain fire blocking between floors which would prevent you from pushing a conduit through. IRC 2012 R302.11(4).

If you were to cut through this in order to run the conduit, you would need to re-apply fire blocking (you can get this in a Great Stuff Spray Foam which makes applying it easy, although messy). Obviously this isn't easily doable without cutting into the walls around the duct at floor level on each floor.

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