Clearances that make a small bathroom work
Most bad bathrooms are not badly finished. They are dimensionally wrong — a door that fouls the basin, a WC you cannot sit on squarely, a shower you step out of into the vanity. These are the numbers we design to.
| Element | Minimum | Comfortable | Note |
|---|---|---|---|
| Clear space in front of the WC | 550 mm | 750 mm | Measured to the nearest obstruction, not to the wall |
| WC centreline to any side wall | 375 mm | 450 mm | Below 375 mm your elbow hits the wall |
| Clear space in front of the basin | 600 mm | 800 mm | A door swinging into this space is the commonest planning error |
| Shower enclosure, internal | 800 × 800 mm | 900 × 1,000 mm | Below 800 mm you cannot bend to pick up soap |
| Basin rim height | 800 mm | 820 – 850 mm | Counter-top basins need the counter lowered to compensate |
| Door leaf width | 600 mm | 700 mm | 700 mm if anyone in the household may ever need a walker |
| Ceiling height under a false ceiling | 2,150 mm | 2,300 mm | Allow 200 mm for the ceiling void if a fan duct crosses it |
Falls, drainage and the ponding test
This is the part of a bathroom that no one sees and every failure comes from. It belongs in the specification in writing, with a hold point you can enforce.
- Set the drain firstThe floor trap and the WC soil connection are the two fixed points. Everything else in the layout arranges itself around them, because moving a soil connection needs a fall of at least 1:40 in the branch and there is rarely slab depth for it.
- Screed to fallA 1:80 to 1:100 fall from the furthest corner to the trap, formed in the screed — not achieved by tilting tiles. In a shower zone, tighten it to 1:60 within the enclosure.
- Waterproof in two coats, up the wallsCementitious or polyurethane membrane, two coats at right angles, taken 150 mm up every wall and 1,800 mm up the shower walls, with a fillet at every wall-floor junction.
- Pond for 48 hoursPlug the trap, fill to 25 mm, mark the level, and check the level and the ceiling below after 48 hours. Photograph the start and end. This is the single most useful hold point in a bathroom contract.
- Then, and only then, tileTile over a tested membrane with a polymer-modified adhesive. Epoxy grout in the shower zone and at the floor-wall junction; cement grout elsewhere is fine.
Get the falls and the waterproofing right and the rest is shopping
Ventilation, which is a design decision not an afterthought
- Size the fan to the room, not the wall. Eight to ten air changes an hour: a 40 sq ft bathroom at 2.3 m height needs roughly 85–105 m³/h. A ₹700 fan moves about 60.
- Duct it out, do not duct it into the ceiling void. A fan discharging into a false ceiling moves the damp problem one metre and hides it.
- Give the air somewhere to come from. A 12 mm undercut on the door leaf, or a louvre. A perfectly sealed bathroom with a good fan achieves very little.
- Run the fan on a timer or humidistat, not on the light switch. Most of the moisture leaves in the ten minutes after you do.
- Windowless bathrooms need a fan on the essential circuit. If there is a generator or inverter backup, the bathroom fan belongs on it.
Lighting by zone and IP rating
| Zone | Where | Minimum IP | What we use |
|---|---|---|---|
| Zone 0 | Inside the shower tray or bath | IP67 | Nothing, generally. If a floor light is insisted on, 12V SELV only |
| Zone 1 | Above the shower or bath to 2,250 mm | IP65 | Sealed recessed downlight, 3000K, 24V driver outside the zone |
| Zone 2 | 600 mm horizontally from zone 1 | IP44 | Mirror light, wall light, ceiling downlight |
| Outside zones | The rest of the room | IP20 | General downlights, cove, decorative |
| Mirror | Either side at eye level | IP44 | Two vertical sources at 1,600 mm centre height, 3500–4000K, CRI 90+ |
A single ceiling downlight behind you at the mirror is the most common lighting mistake in an Indian bathroom — it puts your own face in shadow.
Tile modules and the joint you will stare at
Set the tile module before the layout is frozen, not after. A 600 × 1,200 tile in a 1,650 mm wall gives you a 450 mm sliver in the most visible corner; shifting the vanity 50 mm removes it.
- Start the setting-out from the most visible corner — usually the wall you face from the door — and push the cut to the least visible one.
- Align the floor and wall joints where the tile sizes allow. Where they cannot align, do not half-align them; offset deliberately.
- Keep the niche on a joint. A shower niche cut into the middle of a tile costs more, looks worse, and creates four extra vulnerable edges.
- Decide the grout width early — 2 mm for rectified tile, 3 mm for standard vitrified. It changes the setting-out arithmetic by 30–50 mm across a wall.
- Large format needs a flat substrate. A 800 × 1,600 slab on an out-of-plane wall will lip at every joint, and no amount of adhesive corrects it.
Nobody has ever complained to us about the tile. They complain about the shadow on their face at the mirror and the smell from a trap that never dried out.
Greenbox principal designer
Storage in a 40 square foot room
A well-planned small bathroom holds 14–18 cubic feet of dry storage. The volume comes from four places: a mirror cabinet 120 mm deep, a vanity with drawers rather than a single shelf, a recessed shower niche, and the 300 mm of wall behind the door that is always wasted.
Design, cost and renovation are three different questions
This page is about getting the design right. If the bathroom already exists and has to come out, the sequence, the discovery risks and the phasing are different — see bathroom renovation services. For rates, the itemised figures are on bathroom renovation cost in India, and if you are in Mumbai, bathroom designers in Mumbai covers the society and stack constraints.
Selected work by Greenbox Design Studio. Tap any image to enlarge.
Frequently asked questions
What is the minimum size for a comfortable bathroom?+
About 35 sq ft for a WC, basin and shower laid out properly — roughly 1,500 × 2,200 mm. Below that something has to give, usually the clear space in front of the basin. A 45–55 sq ft bathroom takes a separate enclosed shower and a vanity with real storage without feeling tight.
How much floor fall does a bathroom need?+
1:80 to 1:100 from the furthest corner to the floor trap, tightened to about 1:60 inside a shower enclosure. The fall must be formed in the screed. Tilting the tiles to create a fall produces lipped joints and standing water in the corners within a year.
What is a ponding test and should I insist on one?+
You plug the floor trap, fill the waterproofed floor with about 25 mm of water, mark the level and leave it 48 hours, then check the level and the ceiling below. Yes, insist on it, with photographs at the start and end. It is the only test that finds a membrane failure before tiles go over it.
Which lights are safe above a shower?+
IP65 rated sealed fittings within 2,250 mm above the shower tray, run on a 24V driver located outside the wet zone. Within 600 mm of that area, IP44. Beyond, standard IP20 fittings are fine. Mirror lighting should be two vertical sources either side rather than a downlight above.
Can a WC be moved to a different wall?+
Sometimes, but it is the most expensive move in a bathroom. The soil branch needs a fall of at least 1:40 back to the stack, and in most apartment slabs there is not enough depth to build that in. Where it can be done it usually needs a raised plinth or a macerator, both of which carry their own compromises.
How much storage can a small bathroom hold?+
Fourteen to eighteen cubic feet in a 40 sq ft room, if it is planned. A 120 mm deep mirror cabinet, a vanity with drawers instead of an open shelf, a recessed shower niche on a tile joint, and the strip of wall behind the door together do it without making the room feel smaller.