Best method to waterproof cold joint in partial basement foundation

[ypp]

I have a split level home with an attached 1-car garage. We're demolishing the attached 1-car garage to build a new 2-car detached garage behind the home. Our rec room, which is 1/2 below grade, has an exit to the attached garage. From the rec room you open the door, walk up four steps, and are at the garage floor. We will remove this doorway as part of the demo, and pour a new foundation across the bottom half of the door opening to match and tie into the existing foundation wall on each side.

I'm not super worried about the structural integrity of the new foundation and cold joints, as there's already a header in the wall to support the door opening. I am worried about waterproofing the cold joints. Our contractor is a garage builder who doesn't have experience with this specific item and he is looking to us for guidance; can anyone suggest a good waterproofing method? A specific membrane that's good to use, or a specific epoxy to fill the joints, both, or something else?

I'm a civil engineer myself, but this is far from my realm of expertise. Thanks for your ideas.

an upclose photo

and a bigger view here (steps are in the top right of the photo)

 

[SlideRuleEra]

Bentonite waterstop placed in the joints before the concrete is poured

http://www.cetco.com/bmg/Products/Waterstop/Waterstop-RX.htm

...and for very high water table, bentonitie panels outside the concrete

http://www.cetco.com/bmg/Products/Waterproofing/Volclay_Panels.htm

http://www.SlideRuleEra.net

 

[Ron]

What is it your are trying to waterproof against? Is it groundwater intrusion, surface water runoff, rain down the walls?

Since it doesn't appear that you have an existing water intrusion issue, why would you expect to have one after construction?

In any case, since you'll have every part of the exterior demo area and the area to be filled back in with concrete/masonry, you have many options for waterproofing. For this application, since you have access to the exterior, I would use a coal tar mastic and felt. It's an old method, but there really is nothing better if you have direct access to the wall.

Apply a layer of mastic, embed the felt in it, then apply another layer of mastic. This is called a 3-course flashing and works very well. If you can't get coal tar mastic, use asphaltic flashing cement.

 

[henri2]

Though this has nothing to do with the question posed, I wonder if the landing at door (length measured in direction of travel)complies with provisions of IRC or applicable building code/regulation. In the IBC applicable reference is 1008.1.5

 

[ypp]

Hey everyone, thanks for your replies. Sorry for not making things clearer...

Currently this stairwell goes from the house into the rear part of an attached 1-car garage, so currently it's under a roof. We are demolishing this garage. This area (at the top of the steps) in the future will be a narrow landscaping bed adjacent to the house, with a driveway adjacent to that. So once we fill in these steps and pour the new wall, there will be soil against the new wall and we're worried about seepage through the cold joints.

I'll look into these products - I'm going to call some basement waterproofers in our area, too. THanks all.