Creating a pseudo contiguous poured basement floor

Howdy handy helpers!
Welcome to my first post. Well, my first post in years. I rehabbed a 1936 Bungalow style with the help of a forum such as this. Now I'm back in the saddle, only this time on a much bigger beast.
This house has so many issues I could sell a subscription. Today though, I want to talk about the basement floor.

Despite never being used as such, The Icehouse was built to be a duplex (after serving as an actual ice house) and through multiple additions has 3 basements:
1) SW corner - The original 1809 stone Icehouse - dirt floor, stone walls @9' above grade
2) SE corner - The addition 1888 rendering The Icehouse a residence - mostly dirt, some pedestal concrete, stone walls @9' above grade
3) NW&E corners - The Icehouse's back porch gone addition (19??) spans across the North side of the 2 above mentioned basements - wood joists suspended on stone foundation, stick framed walls, stone foundation @2' above grade

Issues:
The North basement's wood floor joists which span S to N, perpendicular to the back of both South houses are ready to be replaced.
The South basements are insulated by earth on their S side, as they are embedded in the street side. The North basement is only insulated by the South basements, while "exposed" on the North (creek) side with only stick framing.
This is a flood zone. With increased development in the area, flash floods are becoming more of a threat.
The home suffers from compartmental heat distribution (or lack of). The NE corner falls 15 degrees below the room above. It requires a targeted heat source (electric radiator) to mitigate potential frozen plumbing. HVAC is forced/central air and basement vents are in the basement ceiling, providing little to no actual heating to the air space below.

My proposed solution:
Tear out all wood floor joists and associated flooring. Pour a new floor that is levelled and as contiguous as possible to South basements. Include drains to facilitate evacuation of flood water. Embed PEX tubing with the intention of installing radiant floor heat.
(also, insulation of stick framed walls - crucial, but unrelated to floor)

Benefits to this solution include not only a heated footprint, but also a solid flood-proof floor that allows water to pass quickly.

Questions:
1) Will my existing foundation suffer from lateral impact by filling it with a load bearing floor?
2) Ideal vapor barrier/insulation beneath poured floor?
3) Concerns regarding trying to include a drain?
4) What slope is sufficient to promote draining without throwing a washing machine off kilter.
5) Ideally I'd lay an earthen floor - but have chosen concrete for hesitation experimenting with such an old house. Any input?
6) Crawl space door will need to be filled as well...any ideas?
7) This area was once referred to as Pirate's Cove. What if I find a body under there? Or a treasure chest?
8) Can the poured floor connect directly to the existing foundation, or is a barrier required?
9) What kind of retention would enable me to do half at a time...First the NE section, and later the NW section. If this is not feasible, does anyone have a room my inlaws can stay in while we work?

Wow. That's a hefty first post. Thanks in advance for input/advice/tolerance.

Welcome to the site. Back filling is usually or best done with sand and compacted every foot or so as you are filling it, there will be nothing wrong with doing one room at a time. If the foundation is not underground on the outside it is standard to dig down and add foam insulation beside the foundation to the depth of the frost in the area or lay it flat under the floor around the perimeter of the foundation under the slab. When adding heat the concrete floor they lay insulation on the sand under the slab.
As you likely don't have exterior waterproofing and drainage, you might be best to put in an interior perimeter drain and dimpled plastic waterproofing on the walls that extend below the slab so water coming thru the walls goes directly to the drain pipe.

Thanks for the info. So, sand/insulation/slab. Makes sense to me. Should a vapor barrier go in there somewhere, or is that a function of the insulation?

To do this one room at a time, I'll have to build a wall between the E & W sides of the N basement. Is that as simple as creating a lumber wall between? Or should I go for concrete block?

And further still, what concern should I have regarding increasing the lateral pressure on my existing foundation walls?

Regarding the term "backfilling". I've been trying to hone my search terms, so I did some searching just now using "backfilling". Seems like it refers to filling the earth surrounding the home - whereas I am trying to fill the earth inside the home. Am I missing something? Does this term apply to both, and my plan is just so rare that it doesn't pull info?

Footing and foundation are always deeper than the finnished floor so backfilling refers to both outside and inside. I have no experience with a stone foundatin, concerning the pressure, I doubt there would be a problem for areas that are below grade on the outside or just the concrete floor but compacting the sand if it is above ground level could be a problem. You can put the vapour barrier above or below the foam insulation. How deep will your fill be where you are thinking about the seperating wall? You may also want to think about radon venting (Others will have to help you with that)

The existing framed floor is almost 2' above grade, resting on the top of the foundation walls. I could drop the floor height down to grade to avoid interacting with the above grade foundation. It would be nice to get some more room height - but would make the exit door an awkward step up. Might be worth it though.

I think the floor should be level and I would try for that, If you brought it up gradually compacting as you go and when you get above ground, have some one watch the foundation as you compact and be prepared to stop at any stage so as not to damage it.
The picture is the drainage system for a leaky wall.

Cool. Will work toward keeping the floor height as is.

No leaky walls here. But the surrounding developments have been known to send 6' or more of rushing water through our little valley. The flood waters come in by busting down doors and windows. Can't help that, but want to plan for those waters to readily drain.

All the more reason to raise the floor to door height install an outswing door and install the floor to be level with the sill so opening the door prevides the drain to the outside and a min. slope on the floor like 1" .
If this is to become living space, I would still waterproof any walls that are below grade and as you are doing the floor this would be the easiest way. All foundation leak unless they are waterproofed on the outside with a good perimeter drain which I doubt you have.

TheIcehouse1809 said:

...the surrounding developments have been known to send 6' or more of rushing water through our little valley. The flood waters come in by busting down doors and windows. Can't help that, but want to plan for those waters to readily drain.

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Sounds like a bad combination; the rushing waters and living space just don't feel right together. maybe flood control should be a higher priority.

Half is a mud room/utility space, and the other half is a spare bedroom.

Regarding flood control, I have long term plans for flood water mitigation on my property. I have also engaged the county on their part. But unless all the impervious cover in the watershed is matched by on site rain gardens/retention ponds, their runoff will pass by me on it's way to the river.

I like the idea of bringing the floor up to the sill plate. I'll slope toward that...now what about putting a drain in the floor? I have been considering making a concrete form utility sink/shower area in the corner. I can level/slope the floor toward that.

You don't want to run flood water to sewer system or septic tank? You would want a floor drain for a hot water tank.

I don't think I want a sump pump. I lean toward old school solutions. Too much development in too small an area creates a flood problem for the lower district...I don't want to just pass the problem along by sending it to a sewer. And the floods are flash floods. If I build for drainage properly, it should seep into soil rather than run it straight away. Sorry, I know I'm a bit weird here and there. My goal is to create a healthy livable space that can withstand the occasional flood.

All that makes sense but in a flash flood I would think any feild you have set up for disapating the water will it's self be full of water and then you would have no advantage.

TheIcehouse1809 said:

I don't think I want a sump pump. I lean toward old school solutions. Too much development in too small an area creates a flood problem for the lower district...I don't want to just pass the problem along by sending it to a sewer. And the floods are flash floods. If I build for drainage properly, it should seep into soil rather than run it straight away. Sorry, I know I'm a bit weird here and there. My goal is to create a healthy livable space that can withstand the occasional flood.

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I like that you are trying to mitigate the flood water instead of just passing it on. Is the stream/creek the lowest point on your property? Because if it is, then no matter what you do with the water it will find it's way back to the stream. You would have to create a large porous field to capture some of the water, or dig yourself a pond. Be careful that the surface water will not affect your well.

Yes, the stream is the northern line of the property. I've lost more than 10' of land to storm water drainage. But that's another project in itself.
The southern end of the property borders a national road that is probably 15' or more above average stream level. Flood waters have come from both the east (river) and the west (storm water drains), but they will always drain to the NE corner of my property.
I was thinking of putting a concrete form utility floor sink in the NE corner of the basement, where a drain could help move things along. But I also like the floor = door sill solution. I may rock both, unless having a drain from indoors to out would present a problem. I'd rather not drain it to sewer, but recognize code may prevent a direct drain.

It almost sounds like you need an earthen levy or berm of sorts to send the water around your house. It’s honorable that you see the need for collection and retention of these flood waters but you didn’t make the problem you are in the path of it. The overdevelopment should have never been allowed uphill from you without a plan for the runoff water to be slowed and controlled. Sometimes a problem is bigger than the homeowner. Personally I had a similar problem once and it required a neighbor to do some work on his property that he had changed and caused a problem on mine with water. When he was reluctant to do anything I had no choice but to get the township involved at the sight of them he corrected his problem. I would look at this two ways one is protect my property and secondly look for help from the powers in charge to find the correct fix on the big scale. It sounds like its been going on and getting worse for a long time. I can see living with a wet area on one corner of your property part of the year but water coming in and out of the house is not acceptable. I don’t know the lay of your land but if it took a dozer and moving some land around I would at least threaten to do that and see what the county would say.

Up here we have protected farm land in the valley so the cities allowed devopement on the hills and mountains and run off was all over the feilds until a bunch of farmers sued one city and now all the cities have retention ponds. You can have a drain in the floor to the outside but best would be a plastic sump that is made just for that. If you want to keep criters out you put a trap on the drain and a primer to keep the water level up.