... the lower level is 65% earth sheltered but has exterior windows/doors. If your land slopes / drains properly you'll have no water problems.

I have one too and I love the access to the outside and the light downstairs

Dry as a bone - 12 years. There won't be a washout if the ground around it is properly landscaped. Your ideas for drainage are correct... I backfilled the 3 wall of the perimeter with crushed stone after laying perforated pipe around the foundation and tied that in with below floor drainage and gravity feed that out away from the house. Add an extra layer of rubberized roofing (Ice and water underlayment for roofs) at the joint seam between the poured wall and floor. It's self-adhesive and them backfill with crushed rock (after you add rigid insulation to the exterior wall). Shouldn't have any water issues. I don't have a sump pump in the cellar, either.

I split my base roughly in half (2 areas 40 x 13 each). The back room has the laundry, oil tank and furnace, electrical panel, work shop, and storage racks.
Front side has a bedroom and large family room (son's man cave). We have area rugs in the bedroom and family room. Walkout basement.

If we had planed to live downstairs fulltime (like you are doing), I'd have probably run a radiant heat system in the floor - I very efficient way to heat a basement. Another option would be to run 1x3 strips (concrete nail) and using 1" x 2' x 8'strofoam on the floor than plywood or plank over. I'd probably put a watertight seal coating before applying any finish on the floor, though as a moisture barrier.

I think radiant heating uses a heated fluid flowing through PEX tubing under the floor. For some reason I was looking up electric heating which would go under the underlayment and floating laminate flooring -- very expensive electric bill as I recall. Something like 40 watts per square foot. Phew!

PS, just going to be acid stained concrete with a sealer on top of that so a watertight sealer... wait... two coats of sealer? Or just the one?

I'm no expert here - so take whatever I say with the proper amount of skepticism you get for any internet advice. If it were me, I'd probably go for overkill and apply 2 coats. But, honestly, it's probably not necessary if you've sealed the exterior walls properly, particularly that joint between the floor and the poured wall and all other entrances through the wall (sewer pipe, electrical entrance if underground, etc).

I've heard it makes it both lighter and adds more insulation value to the concrete.

I've only seen a finished flooring system where rigid foam was laid down between nailers. My only concern with adding foam pellets would be getting the proper mix consistency. To much pellet concentration might weaken the structural integrity of the concrete and lead to cracking.

That's about all I know on the subject but it's none cheaper than using ICF's (insulating concrete forms).
http://www.foxblocks.com/

but I guess it does. Sort of addresses the need to insultate and create the walls in one step. Nice thing about that approach is that the insulation coverage is 100% - no gaps for infiltration. I guess you'd still anchor interior walls to the concrete?

have lag screws embedded in the concrete where needed and drill holes in the studs for the washers and nuts. I think you could avoid decreasing the insulation value too much that way.

I really like the idea of ICF's, great sound insulation as well as its R value. I'm seriously thinking of Fox Blocks for my next retirement house.

outside of all the basement walls. (Did not do anything to the floor. I am sure it would be even warmer if we had.) I wonder about the infiltration issue with our walls, though, given that we did it this way.

Still, the basement is pretty comfortable. We aren't heating it, but have been able to go down and play ping pong and pool all winter. (Granted, it's not been a typical Maine winter, but I think being below ground it doesn't much matter?) The kids have had parties down there and even ridden their scooter around. It's been great for them, compared to life in the old trailer!

I have seen houses built into hillsides that are awesome, but with my leaky basement, I would have reservations too. I also have so much dampness that this is all I can think about when I think of these houses. I know it is possible to do it, and to do it right. I know that the coolness in summer and the insular earth in the winter is great for energy efficiency. I know all that, and yet, I would have a problem making the decision to try it.

Why don't you think of a straw bale house?

you are using it in wall construction. Any moisture getting into the straw will create structural problems with the framing and become a source for mold/mildew/rot.

IMHO, proper preparation of the foundation before backfilling will avoid leaks/water issues later. In fact, I omitted patching around the sewer pipe exit and ended up having to redig the area out and seal it properly from the outside...it's amazing how much water, under pressure can find it's way into a basement if you don't prep properly...once I fixed that, I've had no water issues in my basement since.

Can you explain a bit more about the sewer pipe exit issue.

We're going to use an old fashioned brick-lined outhouse pit. Actually, "modern" toilets leading out to a pipe about 100' away from the house (and far enough down the hill) so the top of the pit is lower than the bottom of the outlet pipe at that depth -- and lower than the foundation and french drain pipes of course, no backups desired. Putting in a "P" trap then a vent pipe and then the long run to the pit. Any thoughts?

When I built the house it was coming on into December here in Maine and I was starting to take shortcuts in getting things finished. When we opened up the hole in the wall for the sewer pipe it was larger than it should have been and I did a half-assed job of sealing it at that time...I wanted to get the dirt in the hole as things were starting to freeze. The next spring, when the ground started to thaw, water started leaking in around the joint...no amount of oakum could get the leak completely plugged. I lived with that for a couple of years until I finally decided to redig the pipe entrance and concrete patch/seal from the outside.

Since you are putting bathroom(s) in the basement, I assume you'd put the sewer pipe directly through the floor and gravity feed to your holding tank/leachbed? In my prior home (an old rambling farmhouse), we had everything being pushed uphill approx 150' away and 10' above the exit point. That meant pumps to push the septic water out of the holding tank up to the leech bed. That was a miserable situation....I replaced the original pump (in the holding tank) twice - once with the same model and that burned out 3 years later- I realized then it was undersized for the job, then with another with 2x the original rated HP . We had had horrible times with plug-ups etc. When we built the new house (we lost the old farmhouse in a catastrophic fire), we made sure that everything related to the sewer was designed to go as nature demanded - downhill.

I had a situation back 20 years or so ago where we left for a long weekend and lost power - the water pipes froze solid. As soon as I skidded across the floor, I knew I was in trouble - pipes had burst. I didn't know how bad until the heat came on and they started to un-thaw...I had more than a dozen breaks. Lucky for me, the plumbing pipes were exposed so I didn't have to tear out walls to find the leaks. So, I learned how to cut and sweat pipe in a hurry. One of life's many challenges. that's the easy part, though...layout of the proper design and getting it right the first time was something I didn't want to take on...I had a buddy do the work, although I did help. I did most of the electrical wring, though. I laid out and wired all of the fixtures and connected them into the panel - I hired a master electrician to come in and bless it....I only screwed up one of the connections into a junction box.

Or should I just let the pros handle that as well.

It does seem like the way it's supposed to work, I think.

Or, find a buddy who does plumbing and ply him with a couple drinks/beers and pull out your concept for comment.

Nothing I have to mow, however. Maybe just Sedums or other low growing ground cover.

And of course collecting rain water after it's been filtered by the plants is part of the plan.

I'd want to live in an earth sheltered home in that case!

Put in a sump pump to make her happy...

That's tornado, baseball sized hail, and pelting rain country (when it isn't dry as a bone all year that is).

Thanks for the tip on the sump pump. Would that go at the lowest corner?

in my traditional home. I've only needed it a time or two--but that time or two it paid for itself a hundred times over.

When the floor is poured, , a box from boards is made to keep the area free of concrete and lined with crushed rock. Sump pumps are typically designed to operate with a float...when the water in the basin fills to a certain point, the pump comes on and pumps out of the basement until the float drops to the shut-off level. I don't think these are used much today, except if you live in an area where the water table is constantly at or near ground surface level.