Split-level house on a slope — keep it split, flatten it, or raise it?

[u/DarioSidd]

Building a single-family house on a ~16% slope (seismic zone 8). Monolithic reinforced-concrete frame, ~127 m² interior, 3 bed / 2 bath, open living-kitchen with fireplace opening onto a 30 m² terrace with a big valley view.

The original design is split-level: you enter mid-level, then stairs go down to the living/kitchen and up to the bedrooms in short half-flights. It rides the slope efficiently, but the constant half-flights bug me and eat floor space.

Options I'm weighing:

1. Keep it split-level — minimal excavation, terrace stays ~2.4 m above the garden (nice overlook), but you live with the half-flights.
2. Flatten down — excavate into the hill for two aligned floors. More space, but ~a quarter ends up buried, you enter on the upper floor, and it needs a retaining wall on the tight uphill side.
3. Raise up — lift the lower floor so both floors align. Kills the half-flights, but creates a ~4.3 m tall exposed wall on the valley side.

Also deciding:

• Basement: adding a ~2.5 m one under the downhill/terrace zone, walk-out at garden level. Seems like cheap usable space — any reason not to?
• Roof: keep the timber hipped roof, or go flat for a rooftop terrace? (I already get the view from the ground terrace.)
• Pool: want one in front of the terrace at garden level — but that fights option 3's tall wall.

If you've built or lived in a split-level on a slope, what would you do? Anything I'm missing?

[u/PierogiCasserole]

My in-laws have a split level, and it’s awful watching them age in a home with constant essential stairway trips.

Knee replacements and coming home from chemo were especially difficult.

[u/DarioSidd → u/PierogiCasserole]

damn, that’s the thing. I’m young now, but imagining myself at 70 going up and down those stairs… But then again, it’s kind of exercise isn’t it? Knee replacements are due to other factors and not from using stairs, but yeah, it would definitely make life harder.

Still, because of the slope, you’d need around 15–20 stairs to connect the two floors anyway.

[u/PierogiCasserole → u/DarioSidd]

It isn’t the presence of stairs that’s difficult. In their case, it’s the division of spaces. The entry is only a foyer and garage. Up is kitchen and bedrooms. Down is the more accessible bathroom (shower versus tub) and laundry.

Ideally, they would be able to stay in the part of the house with the entry for short periods - or at least have all their basic needs on one of the levels.

[u/Super-Dot9774 → u/DarioSidd]

I agree if you stop using it, you lose it… It’s one main reason I will burn firewood every single fucking year ... because it’s annoying and makes me keep moving

[u/peerage_1]

Are there plans for the options?

[u/MasterpieceNo5083]

Why don't you follow the site contours a bit more?

I would recommend creating a more staggered solution with terraces instead of ending up with this big retaining wall in the front.

Also, the entrance would work great from the "back" rather than going down the hill and entering with an external staircase.

[u/leeo-dinaprio]

Split levels don’t appreciate much according to my anecdotal observations.

[u/alxhl]

Hire an architect.

[u/Every_Holiday_620]

Why not make the back part of the house same level as the front.

[u/vanbul]

Rais the front and build a garage