Bob, I'm not "questioning" the advice, just asking more questions.
I was just down in the basement prepping for the concrete fun tonight. There is 1 wall that will secure into the surrounding existing concrete, and another wall will me 3/4 on existing concrete. The back wall will be 100% on NEW concrete. There are also some shower surrounds that will be 100% on new concrete, BUT I think that I will play it safe and secure what I can to the existing floor, and then secure the walls that are over the new concrete to the ones over the old... Go on my business trip, and then late next Wednesday night or early Thursday just fire a few nails into the new stuff. Seems doable and lets the concrete do its stuff.
I did pick up some accelerator stuff. Gotta factor that into the recipe (starting to think that it would have been a lot better to have gotten Quikrete since it is already mixed and just add water and accelerator)...
Hopefully that will help. Well, time to make some calculations and then off to rent the mixer.
Thanks all!
