Holly I don't know what I said that made you think my primary concern is budget. It is not. Our budget is more than enough for an ICF home with or without basement. However I don't know if building a basement is worth the extra expense or adds any value to our use of the home. We've toured several icf houses that are glorified mcmansion in the area 4000 sq ft monstrosities on basements. I've seen icf basements with traditional construction above and I didn't like them. I love the deep window sills, quietness, energy efficiency, safety ( and the list goes on and on) of an icf home. Traditional stick built is not something we would explore. We have discussed SIPs but ultimately i think we feel most comfortable with the experienced ICF builder. He has over 25 years experience with ICF. He now only builds ICF homes. We toured many of his homes all were well within our budget. But we haven't made the final decision yet. I mentioned the cost because it is a factor. ONE factor not the only or most important factor. I'm not sure if paying x dollars for a glorified storage unit makes any sense. That x would likely come at the cost of tree transplants, koi pond etc. All things we could do in the year or 2nd year after the build, but I would prefer doing now. I also was questioning how the choices impacted the livability and durability of the home. My point in this thread was to understand why people choose one over the other. I've found the answers pretty helpful. I'm not quite understanding the implication building on slab indicates disinterest in quality or interest only in cheapest building process. There is some debate that basements are not a "green" choice. Slab on grade is often used in passive solar homes for the thermal mass of the slab. We want high end finishes in a Eco friendly home. Here is where I'm throwing away money and will never have good resale. Then again we threw that out the window the moment we decided to build a more contemporary bi generational home :) Not every housing choice is about "smart money". Some decisions are a balance between wants, needs, livability and ultimately budget. Per others suggestions we had architect make some changes. It looks like our portion of the house would now be 1920 sq ft on slab with the new utility room and a few other changes to accommodate that room. The inlaw apt stayed at 788 sq ft. Right sized for us. But small by many people's standards. If the home is on basement it would be 1715 as we took out the utility room and didn't need to rework any rooms. Sorry if my original post gave the wrong impression that I was looking for the cheapest option.

I would talk to some plumbers first. My plumber was willing to rent a concrete saw and cut out the sections or have his apprentice do it for an extra hundred or so an hour. But first, he wanted us to hire a company to run a camera through the drains to make sure we knew where they were and that they were all sound. You could probably rent the saw and cut the trenches yourself once you knew where they should be. We patched the trenches ourselves with bagged concrete. There was no need to refinish the whole slab. I tiled directly over it using an isolation membrane. It's been more than five years and we have had no problems.

Thank you for the explanation. You are right I don't like the column or the sump pump. Outside the house is a concrete patio adjacent to the foundation so that would have to come up in order to tunnel under from the exterior. Sounds like we may need to stick with the current U shape (with an island in the middle). My last hope is that when the house was built in 1996 the builder put in a pre-plumb for an island sink option that is hidden under the current island. I've been in a few of my neighbors houses and they don't have a sink in their island but I suppose there's a slim chance its there and most buyers didn't want to pay the tract builder extra money to put in the sink. It was common in the area at the time to pre-plumb for the sink and then charge $1K to finish it. I'll see if anyone on the HOA board knows before tearing things up to check myself.

There are businesses that “trace the plumbing lines”. I recommend hiring one of them. Your need is very common in areas with similar construction. If this is not DIY, I recommend allowing the business you hire to do the work hire the subcontractors.