Horizontal Cold Joint in Concrete Stem Wall

Hopefully you weren't depending on the concrete for tension anyway, so as long as there's sufficient development in the bars above the cold joint you should be fine. If water infiltration is a concern, there should be continuous waterproofing on the exterior anyway - right?

If you don't have enough development above the cold joint to handle whatever tension you have, you may need to have them cut the bars off a few inches above the cold joint, install couplers, and then put hooks in. That would be a bit extreme, though, so make sure you really need it before you toss that idea out there.

Thanks for the reply. Yes, there is dampproofing along the exterior but my concern was if the interface of the new pour may create pockets that may exceed the 1/8” maximum acceptable ‘crack’ width that the damproofing can reasonably span. Probably not much of a concern if they vibrate adequately, but I’ll add a note about maximum allowable crack widths. I’ll take a look at the worst case tension force and see what development length I’ll need. Thanks.

I'd look at having them apply a bead of sikaswell at the middle of the wall. No bonding agent, there's no way the prep work and cleaning would be done properly.

1) If ground moisture can get to the interior face of the concrete, my primary concern with this is a horizontal crack opening up on that face at the joint and causing durability issues. For that purposes, I wouldn't mind seeing #4 dowels at 24" oc or something drilled and epoxied into the joint at the inside face. That, or you get a pass in writing on the liability for any associated corrosion issues.

2) My next, lesser concern would be for vertical cracks opening up where the new concrete is cast against the already hardened, lower concrete. For this, I'd be inclined to put 2-#5 longitudinal bars on each face near the joint in an attempt to keep such shrinkage cracking in check.

3) If the original rebar design worked then I struggle to envision any situation in which the cold joint would cause you any issues with bar development or anchorage. Maybe a shear friction issue because shear friction is a hard ass about development but, even then:

a) Your shear demand for something like this should be low;

b) There are analogs from the topped precast world supporting pretty great longitudinal shear transfer with hardly any interconnection at all.

Thanks for the replies.

KootK, adding some longitudinal bars to prevent vertical shrinkage cracks seems feasible, however, standard construction is to pour concrete stem walls after the footing has cured so wouldn’t that have the same potential for shrinkage cracks where the stemwall abuts the footing? Perhaps I can see if the remaining area of horizontal steel meets the minimum for shrinkage in the cross-sectional area of the next pour of concrete. As for the epoxied vertical bars at the interior face, there is a 6 mil vapor retarder in the crawlspace that runs a minimum of 6” up the inside and adheres to the wall. In addition, the foundation is also vented per the energy code requirements and has an interior drain to daylight, so I’m assuming moisture on the inside face won’t be much of a concern, although this project is in the rainy Pacific Northwest. As for the shear transfer, these are all wood-framed shearwalls usually under 500 plf.

Jayrod, the only time I’ve seen Sikaswell was to prevent water into a basement slab on grade. If I add a layer to the center (which appears on the inside of the verticals since they are slightly towards the soil face) than any water intrusion can still possibly reach the reinforcement before being stopped. I could add a layer on the outside or on either side of the reinforcement but I’ll need to contact Sikka to see if there is a minimum clear distance or a maximum amount since all examples show one line of sealant centered.

Thanks everyone. I appreciate you taking time out to reply.

There is a minimum edge distance, and trust me from my experience, you don't want it outside of your outside bars. You could do a reglet and some of the volclay tape on the outside face of the wall, but from the sounds of it, the cold joint surface isn't very level.

To the point KootK was making regarding shrinkage cracking, do you not have a horizontal bar at the bottom of your stemwall typically? We generally have a horizontal at the top and bottom of every wall. The shrinkage cracking he indicated is a real thing and I've seen it happen on many a 1960s home where they were only just starting to get to thinner concrete basement walls but hadn't provided the appropriate amount of reinforcing to address the potential issues. Sometimes they leak, sometimes they don't. Almost all of the time it could've been solved with a horizontal or two at the bottom of the wall.

Good point. Yes, I do have a bottom bar but this cold joint is very inconsistent and may occur anywhere, so I will definitely add a couple of bars at the bottom.

Thanks for clarifying.

1) jayrod12 beat me to the punch on the shrinkage restraint bars. Where I've practiced, it usually 2-#5 right above the footing.

2) If your vertical bars are outside face and this is a crawlspace, are your stem walls not now nominally basement retaining walls with the rebar on the compression face and a horizontal crack baked in on the tension face? If that's the case, I stand by my recommendation for some nominal, inside face dowelling. It's nice to think that you'd get some adhesion working for you at the cold joint but the same shrinkage stresses that we've been talking about will tend to neuter that.