We are building a slab-on-grade with 420' of walls, about 100' will have about 2'-3' of back-fill about the floor height. With a 4' frost-wall. I am pouring the frost-wall separate, should I pour just the 4', which would put the cold joint below grade on the 100' or so (strongest place to put one). Or should I pour 6-7' for the 100' feet putting the cold joint up the wall, (not as strong but better water-proofing)?

Should we water-proof the whole frost wall or what do ya'll think?

if you could post an elevation that would clarify but I'll throw in my 2c. If its icf I guess I don't understand how it would be any more than marginally stronger and water is the much larger problem as far as waterproofing wouldn't bother below grade as it will move in under the footings ...around here they use 4,8 and 9 ft forms and rarely pour much less than form height. I'm also not familiar with the term cold joint so I assume its the horizontal joint were top of footing meets bottom of wall ....Eric

The entire structure will be ICF with a 4' frost wall below the entire floor. Most of the building will have 12' ceiling, other areas will have 8' and 17' ceilings (wall height clear spans).
My plan was to pour the 4' frost wall; then the 12' walls, 8' and 8' of the 17' walls; then the BuildDeck floor; and finally the last 9'.
But in about one-third of the 12' area the grade will come up 2-3' above the floor on grade. So where do I put the cold joint?
I will water-proof the back-fill area, but what about the other 300' plus of frost wall, what would be the benefit?

Ilgeo has it correct. Strength is not the issue *as long as the lap joints are correct*. Given that, it will have a greatly increased possiblility for leakage, if water gets to it. A good bonding agent helps to mitigate that.

Jerry,
What is your opinion of how to do lap joints correctly?

I have poured the frost-walls, at the concrete floor level, two feet below grade on one side. We are waterproofing all the frost walls. Before any water goes under the the footings, on heavy clay, the water will get picked up by the drain-tile.

Lap splice (not joint) is calculated by not-so-simple-but-once-were equations in ACI 318. CRSI helped develop those equasions, and they have some somewhat simpler tables. Vertical bars are (luckily) the easiest. I'll try to post a simple table on my web site if there is enough interest.

wouldn't a lap splice be shiplaped in design. Icf are you talking about the horizontal joint were the wall sits on the footing? sorry i'm slow to catch on sometimes....Eric