Urinal

We had this in the house that I grew up in and it was an absolute pain trying to keep the downstairs warm in the winter and the upstairs at a reasonable temp. All the hot air went straight up and roasted the second level.

In the summer all the cool air went down stairs and the upstairs stayed hot.

I'd look really hard at this and make sure it's something you can't live without if you decide you need it.

They'll sure take up a lot of wall space

Run extra electrical outlets, and Cat 5 cable outlets throughout the house.
Ensure that the AC duct work is unobstructed, and doesn't have too many sharp turns.
Speakers in the walls.
Remove all the trees that can blow over and hit the house, before I start building.
Install ceiling fan hook ups.
Big shower with a bench seat in the shower for the wife to sit down.
One bedroom & shower downstairs in case someone has problems getting up the stairs.
One strong closet with fireproof walls for gun and ammo storage.
Big pantry for dry good storage.
I would design the living room big enough to allow a big TV, furniture and a computer desk.
May want to think about getting the electrical system set up to integrate solar power. Today solar isn't quite economical, but it will be eventually. Be sure that your roof is orientated in the right direction for solar, & a bracketing system can be easily installed to hold panels.
Put a good floor, some shelves, and ladder to the attic.
If you put in a big garage, make sure that the doors are of good quality. If the doors to your garage blow in during a storm it will rip your roof off.
Storm shutters.

Make a drawing of the house so that you know where everything is, take pictures during construction.

Large screen porches on the water side with sliding glass doors. Washer and dryer on same floor as bedroom. Elevator is a must if two story or more. Cathedral ceilings with all attic space made into closets. Boat lift and covered cleaning station on dock. Standing seam steel roof. Large walk in shower with no door. Pocket doors on bathrooms. Gas range, water heater and heat. Quick disconnects on porch for natural gas grille. Garage big enough to put all vehicles inside.

A bench in the shower is huge. When we redid our master bath a few years ago, the guy didn’t put the bench back in the shower and my wife has bitched about it ever since.

A big pantry that you can walk into is really nice.

you can always add a corner shower seat, depending on layout of shower. women do need a place to shave legs

If you have the space (possibly off the master closet) build your wife a vanity with drawers and a nice light bar above it for make-up and hair.......That way all that jazz is dedicated to one area in the house and you'll be a Hero in her eyes.... This attempt at pleasing her should allow any and all taxidermy in the house to be placed anywhere that you would like to put it...no questions asked... Keep us updated with your progress and good luck...

As already mentioned if its a "forever home" for you wheelchair accessible wide doors.
Requirements for when mine is built.. Spray foam insulation. Radiant floor heat. Quality (insulated) windows and doors. On the interior pocket doors instead of hinged doors.
Your building on a slab Id have a interior storm room made, or if attached garage one of the sunken ones in there.
B/u sources of power/heat , whole home auto genset or at least a cpl of wall gas heaters. The snow storm of 93 left me without power for a week. The only thing that saved us was we had a gas heater that didnt require a electric fan to run.
Exterior, brick, vinyl or composite everything. I dont want to be spending my retirement years painting,caulking, replacing exterior wood, or paying someone else to do it.
No felt paper on roof. Make sure they use the synthetic underlayment.
Pex plumbing.

Just finishing up a 30x40 shop (house is 2500sqft) and wish I did bigger. I highly recommend a water closet and plumbing for a shop sink in the shop. I am really glad I did that. I would also add a lean too for kayaks paddle boats etc if you are on the water. Those things take up a lot of space. Also anywhere you can make attic space to store stuff is a plus. Helps with resell too.

Barn doors are a fad and as doekiller said do not block sound well.

My uncle put an elevator in his house, and in hind sight, it was a very smart investment. He was wheelchair bound in a couple of years after they finished building. He had an accident pulling a stump out of the ground in his tractor.

If you do spray foam, I recommend getting a multi-stage HVAC. I have spray foam and spent the extra coin to get a multi-staged unit. Its nice in the summer when the AC runs on the lowest stage, keeps the house nice and cool, keeps the humidity low, and the power bill is cheap.

Not going to read 8 pages to see if this has been mentioned -

Laundry Room/Mud Room off the garage and the Kitchen off the garage. Walk through laundry to kitchen is the way my house is setup and I will never live in a house setup any other way. I use to have the garage in the basement and have to take the groceries up the stairs...

Never again. Love a big single story home.

Make sure your tankless w/h are plug in and not hard wired. When the power goes out you can plug them in a generator. If you are having a generator installed for the house that would be better.

I have heard if you get a hvac system that takes the humidity out of the air it works better. And if your on a septic system, run your gray water out somewhere ( if allowed)

Here’s what we did on our last house.
2’ soffits for better attic ventilation and shade over windows
Insulate all interior walls for sound proofing between rooms
2x4 (vertical & flush to stud edge) between studs where you think you will hang heavy objects
Caulked every exterior wall
Walk-in shower without a glass door. Add glass block to allow light to come in.
Overhead heat lamps in drying areas of the shower/baths
Use 4way instead of 2 way plus outlets...you’ll thank me later
No 2 story house, one story only as you get older you’ll be glad you did
36” or more insulation in the attic
Hose bibs on every exterior wall
Metal studs in all wet areas like bathrooms and laundry room

Goodluck these days with custom home builders, you’ll be better off managing the build yourself.

yes, a combo storm room/survival room.

Also, perhaps steel framing to better withstand tornadoes and hurricane force winds.
I know that is expensive, but if I ever build a house from scratch I am going to use them.
It is some kind of steel 2x4. I saw it on TV.

And those roof tie down things that they developed to help roofs better withstand high winds.

My uncle has a storm shelter under his garage.

Those waist high horizontal handicap bars in the shower are real fun if your ol lady is small enough to set on top of it. You can really get some leverage

And “Bam” here we go...

Elevator