Mmmk, so i got this situation;

part will be new wall, part existing old wall. old wall probably has pretty crappy condition tar on it. need to get new waterproofing on, attach xps to that, and water barrier over the whole thing.

sounds simple right.... well if it does to you, you must know something I want to know! lol.

I'll be doing this myself, and on a very limited budget, so i need to know what to use, how to use it.

so far, my thought pattern is something like this;

1. Have no idea what to use here for the actual waterproofing of the block... Asphalt will crack if wall cracks, don't like that. So figured maybe rubber coating or something, but what? how much does it cost? can i affix the foam right to that, or should i use fasteners? what to i seal around the fastener holes with?

2. do i need to waterproof where the block meets the footing? or is water at the footing level ok?

I think i just had an epiphany

So if i didn't have the footing all sealed up tight, and the water table was high, even if my wall was holding the water out, the water could come through from underneath the footing and floor, is that correct? That seems like it would suck awful bad. Obviously that is what the drain tile is for, along with the sump, however, if those worked all the time, no one would ever get hydrostatic pressure on a wall though would they? Ok, im lost now...

3rd thing was supposed to be how to i affix a real water barrier to the wall, how and where should i attach it on the bottom, and with what? and what should I use? was thinking 6 mil poly as it is cheap.

Basement water is no fun, I have been there on my own 1960 rambler with a CMU foundation. When we added on and remoulded with an ICF foundation (like there is any other way); I had the whole foundation excavated, flushed up the ICFs with the CMUs on the outside and put on a peel and stick membrane down onto the footings, after priming and put XPS OVER the membrane. the XPS provides insulation (needed over the CMUs) and protection for the membrane. Then drain-tile to daylight (not always possible). But if I was doing it now; I would try to use InSoFast over the CMUs and flush the ICFs with the InSoFast. Install a peel and stick membrane over the ICFs and InSoFast, then a dimple membrane over the peel and stick, and maybe a protectant board over that depending what is in the back-fill that could hurt the system. Drain-tile (close to the footing) with course rock, compact back-fill in 1' lifts.

Hmm, are you saying that you encased your existing home's CMU foundation in a new ICF one? I might have misinterpreted but that seems like sheer genius to me if you did and I would want to know every detail!

I've heard the name insofast before, if i recall they are an ICF type, what makes them better than anyone else like quad lock or standard or the million others that pop up daily?

For my own foundation I'm probably going to stick with the cheap CMU's, I don't have much money to work with here, even 80 bucks a square foot would be far more than I could afford.

I'm still torn on whether to use the rigid on the inside or outside of the walls, I can't get to all of the old walls, like the one under the garage for example, there just isn't any getting to it from the exterior, being as such, even though there are only a few, i figured that the thermal bridging might negate whatever I did on the exterior anyway, and thus I'm leaning much toward creating an interior shell on the basement and skipping the exterior below grade entirely.

Insofast is not an ICF, It's......It's..half an ICF. you glue, nail or screw the foam panels to your foundation.

I have used InSoFast, and it is a very good product.