I agree with Wanda Kubat-Nerdin - Wanda Can! 

That said, slab has a downside when a pipe breaks or needs replacing. We don't see basements in new construction. 

3. Slab on grade with upstairs is more affordable to build due to less concrete and labor cost and smaller carbon footprint.

Absolutely #3 - (Smaller footprint on slab with some square footage moved to second level in roof space, i.e. 1.5 story home.) Basement homes are quite expensive to build here due to the clay soil - dry-proofing and digging out are more expensive than building up and on a slab.

My guess would be #1 ranch on a slab.  Single story homes tend to be cheaper to remodel than two story homes for some reason.

I'd check with a few builders and see what the bids come in at with the various designs.

a ranch style home is the most expensive to build because it's cheaper to go up than out.....the roof system and foundation is more expensive than a 1.5 or 2 story building....

the cape style home would be the least expensive because there's a second floor.....and it's cheaper to go up....  

it's even less expensive to build a two story home...colonial style.... the framing of a cape is more expensive than a colonial.... 

It depends on which builder you hire. Cheapest could be a modular on block crawlspace with 2nd story. But from your choices, # 3 would probably be cheapest.

Corinne,

It depends, I do not like slab foundation because it is hell if something needs replacing, so nothing is saved.  We have always had raised foundation/no basement.  I am not a fan of cheap anything, I believe in doing it right in the first place so that a home lasts.  In the long it is cheap...A

We do not see much new slab construction in our area.

Cheapest way is modular construction, even cheaper is a slab over a foundation and basement. 

1

I know about condos only...

I have no construction experience to draw from to be of help.

I'm going with #3 Corinne Guest .

Slab with a second floor is probably the cheapest way here.

Not a fan of two story anything as my family is grown and I like E-Z-P-Z...Go pure function i.e. closets galore, storage, large two car garage with work-space, garden for back yard and simple maintenance for front yard. No high end appliances and large hallways. I prefer crawlspace but slabs work. Lots of windows, good insulation and security system. Now you are all set

It could be either 1 or 2 here... land is expensive so that would be a determining factor in cost. We have no basement homes here... unless it's a walk-out basement and then you pay a huge premium for a basement lot.

OK Corinne.  This is a trick question.  Here in Florida we have a high water table and cannot build basements so we normally build on a slab either on grade or a few concrete block courses up and fill under the slab.

I think you might be getting to a question about taking X square footage and asking if it is less expensive taking half of it upstairs for a more compact plan and potentially less expensive construction.

Here are a few pros and cons that come to mind...

If you plan on an expensive roof then cutting half of it for a two story would save you money.  You would also save on the concrete slab.

If you put some bedrooms and baths upstairs you will need a stair and floor joists.

A two-story plan can be a little slower to build than having all trades on a single ground floor.  Cost for all subcontractors to work a second floor is theoretically more expensive as well.

A compact two-story plan will limit the total perimeter wall by 15% or more which means less siding, brick or stucco.

A compact plan tends to offer control of heating and cooling costs.  In hot and cold climates you should have a lower energy bill. If your kids leave for college and the master is downstairs you can limit costs of heating and cooling upstairs.

On a 2,500 SF home you can possibly deal with a single heat pump but zoned areas with two units are ideal.  

For stay in place use by aging homeowners the second floor is not attractive.  In Florida with so many retirees, even large mansions (especially in Naples area I have seen) are spread around on one level for this reason.

If you have an architecture of steep roofs (some bungalow styles, Tudor or French styles) you can build some space under the roof. This means though that you cannot use a full attic plenum to mitigate heat and cold and that a very effective insulation has to be installed into the space between rafters.

My bottom line: for the size of a 2,500 SF house, keep it one story.  You would have to go a few hundred square feet higher to realize overall savings as described above.

It is always cheaper to go up.

800 SF on three levels. In Florida it would be 800 SF on 4 levels with ground zero being the garage, and house constructed on peirs. Basements in coastal Florida become indoor pools.

No, that I won't be able to answer. Will read answers.

Interesting answers.  Maybe John Henry could respond with his expert opinion to further advance your existing knowledge or to further confuse you.  Good luck. Ditto Ken Semler who could provide his professional opinion regarding modular.  

4. Modular

We are seeing more homes without a basement to keep costs down.

We only have some slab homes here at all, both one and two storey. Most are not built on slab due to earthquakes.