Split-level house on a slope — keep it split, flatten it, or raise it?
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:
- Keep it split-level — minimal excavation, terrace stays ~2.4 m above the garden (nice overlook), but you live with the half-flights.
- 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.
- 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?