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Baseboard rough-in piping

Ewan Member Posts: 45
I'm a homeowner currently working-out the details for a retrofit hydronic baseboard installation. I hope to do some of the work myself, while hiring a contractor to take care of those aspects that demand a professional.

I've been looking at how best to route the rough-in piping for the baseboard radiators on the exterior walls.
As the attached section-drawing shows, the exterior walls are offset to the outside of the foundation, with no access from underneath. The closest I can get with a hole from below is inset a minimum of 4-1/2" from the drywall, and this would require clearing-off the XPS in this area.

Blocking the baseboards off the wall with site-build 'boxes' has been suggested, but this is obviously not ideal aesthetically or from a floor-use perspective. Cutting/drilling/gouging channels in the concrete might be possible, but ugly. There is no exterior insulation on this above-ground portion of the foundation, so the piping would have a very short run through uninsulated concrete.

Has anybody dealt with a situation like this before?
Any advice or suggestions would be most appreciated.


  • Paul Mitchell_2
    Paul Mitchell_2 Member Posts: 184
    I see the external

    2x8. So you are saying that there is concrete in between the floor joists? If that is the case that is a tough one. The drawing looks as if it were normal construction. Sounds perfect for radiant heat. Depending on the type of baseboard your hole would be in the floor about 1 7/16 off the sheet rock. According to you it will still hit the concrete?
  • A thought

    You might consider running the return pipe in the cabinet of the baseboard, and come up through the floor on an inside wall, 2' off the corner of the wall that you want to use. Put in an "L" shaped run with two lengths of baseboard and an inside corner, with the pipes coming up and back down on the two footer on the inside wall.

    Or something like that...

  • Weezbo
    Weezbo Member Posts: 6,232
    Noles idea, is sound. its done every day,all over the world.

  • Ewan
    Ewan Member Posts: 45
    Floor Construction

    Hi Paul,
    Yes, there's concrete between the floor joists; the joists sit in 'pockets' in the foundation wall. I gather this 'imbedded' joist construction was used during the era the house was built (late 1940s, Ottawa, Ontario).
    I would need to drill a hole minimum 4-1/2" off the sheetrock to avoid hitting the concrete.

    Any thoughts?

  • Ewan
    Ewan Member Posts: 45
    Thanks Noel

    for the suggestion... hadn't thought of that. The 'L' shape would probably work in a couple of spots. The house has a small (<1000 sq.ft.) square footprint so there aren't too many interior partitions.
  • hr
    hr Member Posts: 6,106
    Sounds like you are between a rock

    and a cold spot! Odd framing detail, how did that come about?

    I like the L shape idea, with return in the board, also. Unless you could bore some angled holes with a concrete core bit. Probably need a GPS to have them come out in the right location when drilled from below :)

    Watts Radiant Onix EPDM can be a real lifesaver when funky baseboard installs are on the table. 1/2 Onix can do some wild tricks if you are rubber comfortable :)

    hot rod

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  • Ewan
    Ewan Member Posts: 45
    Thanks hot rod

    for the reply... it's a bit of a odd duck that's for sure. Not sure why they decided to build that way at the time, but most every house in my neighborhood is framed the same way.

    Assuming I could bore an angled hole through the concrete, should I be worried about running pipe through that short uninsulated section?
  • hr
    hr Member Posts: 6,106
    I would not worry

    about that short section if the space below is heated. You could overbore and insulate.

    A radical idea... Bore up through the floor joist, at the correct angle! This way you are boring woods not concrete. Scab a new joist against the bored one and hanger off the foundation wall to maintain the joist strength. Or header off the drilled one to the two on either side. The bb could still run to the wall just shorten the element to lign with the holes.

    The concrete bore would be tricky when you bump up against the bottom of the wood floor build up. Most concrete drill shudder at the sight of wood. You would have to drill the concrete then switch to a wood bit. Sounds like a pain. I'd rather get reved up with a long ship auger and go for the gold in one motion :)

    Gotta be a way to get from A to B if there is a will :)

    hot rod

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  • Jon_2
    Jon_2 Member Posts: 109

    Assuming your hook-ups will be with 3/4" Onix (1 1/8" od). First using a hole saw. cut an 1 1/2" hole through the hardwood and underlayment. Then with a hammerdrill,(big Hilti)drill a 1 1/2" hole 4-6" down, then in the cellar use a 2" drill perpedicular to connect with the 1 1/2" hole. Then run your Onix to connect up. I live between Massena and Ogdensburg NY and I know what our winters are like, so I would anti-freeze the system. Before drilling the first hole I would insure its location in regard to the floor joist by running up a small pilot hole in front of the basement wall and use that to locate all other holes. Make it small enough to plug and keep the head of the household happy. If the hammerdrill is a good one the holes in the concrete are easy, the worst it using the stinking hole saw to cut the hardwood and underlayment. Use a hole saw with a plug ejector.
  • Robert O'Connor_7
    Robert O'Connor_7 Member Posts: 688
    Why not..

    Drop feed? Might be alot of pipe and a little more pump but wadaya gonna do? Is there an attic? Snaking pex down a wall you might have firestop issues but fixing sheetrocks alot easier than the floor...Robert O'Connor/NJ
  • Ewan
    Ewan Member Posts: 45
    Is drop feeding

    down a 2x4 cavity-insulated exterior wall advisable? The design temperature here is -20°F, and we can get a few weeklong stretches that are easily that cold during the winter.
    No question, running tubing down the wall is probably less futzing around than boring through the concrete, but I understood keeping all plumbing out of the envelope walls was key.

    Please set me straight Robert if I'm wrong.

    Thanks to all for the feedback... much appreciated.
  • bob young
    bob young Member Posts: 2,177

    if you insulate properly you can even put it outside
  • Robert O'Connor_7
    Robert O'Connor_7 Member Posts: 688
    just a suggestion...

    There are more than one way to skin the mother-in-law. Running any tubing on an outside wall and being exposed to freezing conditions is never advisable, although the right tubing, installed as far inside the insulated cavity as possible, and adding anti-freeze just might work. Ideally I'd probably keep it all in the heated space, or bite the channeling the floor bullet. Certain pex products, if frozen will swell an enormous amount and not burst when frozen, you just make sure it doesn't. Money is an amazing bringer of crazy ideas.. Good Luck!.Robert O'Connor/NJ
  • If outside is outside the heat and insulation

    I don't agree. First power failure would put you out of business.

    Keep it within the envelope. I'm a little nervous about even putting it in a hole through the concrete that is insulated on the INSIDE.

    I agree with the advice that you recieved locally.

  • Dale
    Dale Member Posts: 1,317

    On those spaces where noels idea isn't a good fit I would just drill a tiny hole through the woooden floor to find exactly where you're at and then rent a commercial roto hammer and drill the concrete down and sideways from the basement, no more than a few hours work with a large spline drive hammer. About 1 1/4 or 1 1/2 inch down and larger from the side depending on what you can rent. Then soft copper stub to get into the basement soldered on to a 45 el with hard pipe up to the rad. You can put on pipe insulation prior to putting it in or spray in foam if you're worried about freezing and heat loss to the concrete. Since you have time you could mock this up in wood to know the ideal size of fittings and holes. This is doable since the concrete between the joists isn't really structure supporting.
  • hr
    hr Member Posts: 6,106
    Keep in mind

    you may be able to feed those bb's with 5/8" or even 1/2" PAP or EPDM. If the loops are short and the loads low.

    Run some calcs to see what tube size you really need. 1/2 or 5/8" PAP is a very nice tube to form around curves for bb installs. It doesn't tend to put strain on the fin tube like regular pex does when alignment is not perfect. 3/4" pex can be a bear to work with in close couple connections like bb.

    Also check into Slant Fins flexible copper connectors if you really prefer, or need, 3/4" copper for you connections.

    Hydronic antifreeze is always an option if you are able to keep an eye on it every few years.

    hot rod

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  • Doug Wagoner
    Doug Wagoner Member Posts: 78
    Threading down from the attic

    is a difficult task. The close quarters where the slope of the roof pinches the attic to nothing will not allow one to work piping near the eaves. Avoid the attic route.
    You can lay out the holes on the top side by having someone below with a magnet between the joists while you locate the magnet with a stud finder (I have used a compass also) from the top. Both of you mark the determined location with approperate marking devices.
  • Jed_2
    Jed_2 Member Posts: 781

    Your cross section presents limited options. A floor plan view of the room in question would give a perspective of creative options. A cabinet or piece of furniture which would allow an access from inboard of the concrete wall. Or a wall partition to create a small chase at floor level(it would only be about 5"). Build a bench seat of some sort. Anything to "create" an aesthetically pleasing avenue from which to drill the floor panel only.

    Just trying to be creative. There must be some interior avenue, unless the room is naked.

  • Nick Z._2
    Nick Z._2 Member Posts: 32
    Surround the outside walls

    I would run B.B.around the whole interior.Use some blank if you want, with any luck you might be able to figure a way you can only have to drill 2 holes thru the floor.
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