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Thread: 2x4 frame bottom plates issue

  1. #1
    DIY Senior Member diyfun's Avatar
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    Default 2x4 frame bottom plates issue

    I have interior french drain around the basement concrete wall. In many places the concrete are less than 1" in thickness. we couldn't go deeper because the foundation doesn't have footing.

    If we use Tapcon, it may damage the french drain and it may also not hold well. Is there another way to fix the bottom frame plate? or i can leave them without mechanical connection with concrete floor.

    Any suggestions?

  2. #2
    Plumbing Contractor for 49 years johnjh2o1's Avatar
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    You could fasten two 2x4's with 1/2" plywood in between flat against foundation wall and start your framing from there.

    John

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    Test, Don't Guess! cacher_chick's Avatar
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    Particularly if you are insulating, there would be nothing lost (except a little bit of square footage) if you build the stud walls further to the inside of the exterior walls. In many basements you will find that the concrete walls are not plumb from one end to another, so you will need to come inwards to keep everything straight anyway.

    If you are planning any plumbing below slab, don't forget that it will need to be inside of the footing drain also.

    I don't understand how a basement wall cannot have a footing......

  4. #4
    Moderator & Master Plumber hj's Avatar
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    A basement wall without a footing is a disaster waiting to happen. Even if your anchors penetrated the "French drain" it would NOT damage it, unless you used a red clay tile pipe.
    Licensed residential and commercial plumber

  5. #5
    DIY Senior Member diyfun's Avatar
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    Quote Originally Posted by johnjh2o1 View Post
    You could fasten two 2x4's with 1/2" plywood in between flat against foundation wall and start your framing from there.

    John
    Are you saying fasten the 2x4's with the concrete wall?

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    DIY Senior Member diyfun's Avatar
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    Quote Originally Posted by hj View Post
    A basement wall without a footing is a disaster waiting to happen. Even if your anchors penetrated the "French drain" it would NOT damage it, unless you used a red clay tile pipe.
    you are right, the plastic pipes should be ok but if the concrete cannot hold the Tapcons well, why I need those Tapcons?

  7. #7
    Test, Don't Guess! cacher_chick's Avatar
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    The tapcons I am familiar with would not have the shear strength to be suitable for this type of application. You need to think about things that happen in a house- I.E. kids roughhousing, furniture getting pushed against the wall, etc. One situation that I vividly remember was a carpet installer using a carpet stretcher. When he applied pressure against the baseboard, he pushed the entire finished wall in because it was not nailed properly.

    We always use 3/8" Red Head Wedge Anchors when setting walls on concrete. The bottom plate should also be treated lumber unless you are using sill plate gasket or something similar to keep the wood up off the concrete.

  8. #8
    DIY Senior Member dlarrivee's Avatar
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    I'm really shocked here...

    Who cares how the 2x4 stud wall SHOULD be built, if that house is honestly missing footings, why bother doing anything inside it?

    Bulldozer.

  9. #9
    Moderator & Master Plumber hj's Avatar
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    Do you have any idea how much force it would take to "shear" almost any fastener when the two surfaces are in contact with weight on them? That wall was NOT improperly nailed, it was not nailed at all.
    Licensed residential and commercial plumber

  10. #10
    In the trades Dana's Avatar
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    The studwall is not structural- it's not supporting the house, and only needs sufficient strength to hold the wallboard and cavity insulation. Mechanically ins a near-zero load. The gypsum is required as an ignition barrier against your wall-foam.

    Run your floor foam all the way to the wall foam, and tapcon the subflooring to the slab a foot or so away from the edge ~24" o.c. or so, then nail the studwall plate to the subfloor- DONE! It's not going anywhere.

  11. #11
    Test, Don't Guess! cacher_chick's Avatar
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    But in this case the new wall might eventually be holding the house up, as the OP states that there is no footing under the basement walls.

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    DIY Senior Member diyfun's Avatar
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    Quote Originally Posted by cacher_chick View Post
    But in this case the new wall might eventually be holding the house up, as the OP states that there is no footing under the basement walls.
    I have asked few experts. I was told it was not illegal to build a house without footing if the foundation soil was very stable back in 1950s. There is no single crack on this 60yrs house. That indicates it can still stand up for another 60yrs or so. I am not worry about this. So when I put the french drain. I used two 2" pipes to avoid a deep trench. I think this house is sitting on an old beach. When i dug hole for sump pump basin, which is at least 5' away from the wall, I found i was on a beach with lots of small rocks/gravels. The basement is a full basement. it is unlike a refill layer.
    Last edited by diyfun; 04-09-2012 at 08:07 PM.

  13. #13
    DIY Senior Member diyfun's Avatar
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    Quote Originally Posted by Dana View Post
    The studwall is not structural- it's not supporting the house, and only needs sufficient strength to hold the wallboard and cavity insulation. Mechanically ins a near-zero load. The gypsum is required as an ignition barrier against your wall-foam.

    Run your floor foam all the way to the wall foam, and tapcon the subflooring to the slab a foot or so away from the edge ~24" o.c. or so, then nail the studwall plate to the subfloor- DONE! It's not going anywhere.
    Great! I like this idea. Thank you indeed.

  14. #14
    ACO Shower Drain Sales johnfrwhipple's Avatar
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    Quote Originally Posted by dlarrivee View Post
    I'm really shocked here...

    Who cares how the 2x4 stud wall SHOULD be built, if that house is honestly missing footings, why bother doing anything inside it?

    Bulldozer.
    Seriously. Bulldozer?

    My home was build in the 60's. In North Vancouver and served many families well up until two years ago when we ripped it apart.

    No footings.

    None.

    No rebar in the foundation walls as well. This was common back in the day.

    There are many ways to attach to the bottom plate to the slab. Consider attaching some 1/4" cement board to the bottom plate first and set the 2"x4" with thinset. You might use some waterproofing over this one stud to stop moisture migration.

    Building the wall a little tight and installing over a 3/4" ridgid foam insulation works. If the new wall is not bearing any weight.

    Building the wall a little light on the measurement and using spray foam to attach it top and bottom works as well.


    jfrwhipple@gmail.com - www-no-curb.com - 604 506 6792

    Always get construction advice double checked by your local city hall. Flood Test Every Shower - Every Time.

  15. #15
    In the trades Dana's Avatar
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    johnfrwhipple: He's already building it with more than 3/4" of foam on both the wall and the slab, and it needs to be more than 3/4" in his climate. With only 3/4" he'd be putting the studs at risk for mold growth from either wintertime condensation on the cold foam.

    An interior vapor retarder would cut the wintertime load, but raise the average load from ground moisture, which he clearly has, so to be safe he has to skip the poly, and keep the average winter temp at the foam/fiber interface above the interior dew point of design interior temp of 21C/35% relative humidity, which is +5C. This would not meet code in Canada, which requires the foam/fiber interface to be above +5C at the outdoor design temp, not the winter average temp. But in any climate warmer than Saskatchewan it would lower rather than increase mold risk with this approach.

    His average winter outdoor temp is about -4C, so with R13 batts in the studwall and R3.75 (3/4" XPS) the average temp at the foam/fiber interface on the above-grade section would be:

    -4C + [(21C- -4C) x (3.75/(3.75+13)]= +1.6C

    which is well shy of +5C.

    Bumping that to 1" would be code-legal here, but only yields about +3C.

    At 1.5" XPS (R7.5) or 2" EPS (R8) hie's in good shape though:

    -4C + [(21C- -4C) x (7.5/(7.5+13)]= +5.1C

    Any condensate that forms on the above grade portion in the overnight hours or during cold-snap re-evaporates before reaching the stud plate.

    Vancouver's average winter temp is about +3C, but the wintertime interior moisture is also much higher, so it's safer to design for the dew point of 21C/40% RH air, which is +7C.

    With 3/4" XPS you'd have:

    3C + [(21C- 3C) x (3.75/(3.75+13)]= +7C, which is perfectly safe...

    ...but not code-legal without interior poly in Canada.

    To meet code in Vancouver (outside design temp= -4.5C), if you bumped that to 1.5"/R7.5:

    -4.5C + [(21C- -4.5C) x (7.5/(7.5+13)]= +4.8C

    That's close enough to code legal without the poly that it should fly with inspectors, but you could use unfaced low density R11s rather than R13s, or unfaced 2"/R8 EPS rather than R7.5 XPS if they're they type that want to quibble.

    In Vancouver I'd either do that, or use 2.5"/R10 EPS or 2" XPS held in place with furring through-screwed to the foundation on which to hang the gypsum for a thinner stackup.

    In my own home (not too far from diyfun) I went with 3"/R19 fiber-faced iso + furring. The footings in my house are fully saturated with water 4-5 months of the year (high water table), yet the foundation dries adequately through the somewhat-permeable facers of the foam to keep from rotting out the foundation sills. If I went with foil-faced or poly I'd have to jack up the house and insert membrane capillary breaks under the foundation sills to protect them from ground moisture.

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