How small can a bathroom be and still work well?

A functional bathroom can work in as little as 5x8ft if the fixture cluster follows the existing plumbing and the vanity is sized to the wall it occupies rather than to a wider reference layout. Below that, compromises on the shower zone usually become unavoidable.

Should the vanity or the shower be planned first?

Neither, strictly speaking. The WC and the shower drain are fixed by the builder's plumbing and cannot move without breaking into the slab, so both get planned around those points first. The vanity is the one element with real flexibility, which is why its design deserves the most attention.

Is marble a practical choice for an Indian bathroom?

Honed marble works well on bathroom counters and walls when it is sealed on a regular schedule, since the concern there is water exposure rather than the acidic staining that rules it out in a kitchen. It should still be avoided on floors prone to standing water without a slope.

What is the most commonly overlooked detail in bathroom design?

Ventilation and electrical placement outside the wet zone are the two most frequently under-specified details, since neither shows up in a photograph the way a vanity or a mirror does.

Bathroom Design for a Compact Flat

Bathroom design in a compact Indian flat starts with the drain, gas and duct positions the builder has already fixed, then works outward to materials that survive daily steam and a vanity sized to the corner you actually have.