Guide

Lighting thumb rules that survive contact with a real room

Four numbers that decide whether a room is lit, and why the fixture you were going to buy is the last decision.

Why your rooms feel dark even with the lights on

You walk into a newly built room and flip a wall switch. A single bulb in the middle of the ceiling turns on. The centre of the floor is bright, but the corners are in shadow. When you chop vegetables at the counter or sit at a desk, your own body blocks the light.

Most house plans treat lighting as an electrical afterthought. People mark a junction box in the middle of each ceiling slab and assume the room is lit. You end up buying floor lamps, extension cords, and extra tube lights to fix dark corners after moving in.

Rewiring a finished house wastes time and money. Chasing conduits into cured masonry ruins plaster and weakens walls. Fixing lighting before the concrete pour costs nothing. Fixing it after you move in requires surface trunking, chipped plaster, and repainting.

The daylight and fixture rules you must measure to

Every lighting layout starts with the sun before you place a single wire. Artificial light only completes what natural openings miss.

The National Building Code Part 8 states that every habitable room needs openings on two different faces to be ventilated. That rule also dictates daylight. A room with windows on only one wall leaves the opposite corners dim. Two faces balance daylight across the entire space.

Climate geometry at 8–16°N shows that north light carries no direct sun. You can open the north wall generously for clean daytime light without bringing in midday heat. The west wall takes afternoon sun at about 18° when daily temperatures peak. That wall gets the smallest openings.

For windows, climate geometry at 8–16°N requires an external shading projection of at least 600 mm with a 900 mm sill. At 8–16°N, eaves depth must measure 900 mm. At 16–24°N, eaves depth is 750 mm. At 24–36°N, eaves depth is 600 mm. External shading stops heat and direct glare before it reaches glass. Our practice notes that curtains stop nothing once heat enters the room, but a 250 mm curtain overrun past the reveal ensures fabric clears the glass when opened.

Fixtures follow the working plane and the line of sight. In our practice, a TV screen centre sits 1.06 m above the finished floor. Seated viewing distance must be at least 2.5 times the screen diagonal. For room airflow and ambient light, our practice centres the ceiling fan on the room centre, not on the bed.

How to layer light across each room

You cannot solve room lighting from a single point on the ceiling. A centre ceiling box is the least useful layer in a house. It casts shadows over every counter, desk, and mirror arranged against the walls.

Plan your illumination in three steps:

• Openings first. Use natural light from two wall faces.
• Surfaces second. Define the work surfaces and furniture zones where light must land.
• Fittings third. Place task fixtures directly above working planes.

In the kitchen, work counters stand 900 mm high and 600 mm deep. Upper wall cabinets are 350 mm deep, set with a 500 to 600 mm clearance above the counter. A ceiling fitting behind you casts your shadow directly across the chopping board. Task lighting must sit under the upper cabinets to illuminate the 900 mm high counter below. Provide task clearance at the hob, which requires 500 mm of landing space on either side.

In the dining area, task lighting belongs directly over the table surface. Our practice allocates 600 mm of table edge per person for elbow room. Pulling out a dining chair takes 750 mm to a wall or 450 mm to a walkway. A fixture dropped over the centre of the table marks the zone and leaves the surrounding circulation clear.

In the bedroom, keep ceiling lights away from your sight line when lying down. Our practice requires bed heads to rest against a solid wall, never shared with a bathroom or kitchen, and never under a window. General circulation paths need 914 mm of clear space, matching the National Building Code Part 3 minimum. Clear floor space beside a bed requires 914 mm preferred on each side, with an absolute floor of 600 mm only on a secondary side. Low wall sconces or bedside lamps illuminate reading zones without flooding the 914 mm bedside passage with glare.

The mistakes this prevents on site

The most expensive mistake is cutting chases into finished walls. Our practice notes that conduit, back-boxes, and extract ducts must be built in as the walls rise. An earth, lime, or masonry wall cannot be chased afterwards without structural damage. Cutting into completed brickwork weakens 110 mm partition walls and cracks plaster.

At average 2026 construction costs in India, basic finish runs ₹1,600 to ₹2,000 per sq ft, standard finish runs ₹2,000 to ₹2,800 per sq ft, and premium finish runs ₹2,800 to ₹4,500+ per sq ft. Reworking electrical points on a 995 sq ft house adds direct labour costs and ruins wall finishes you already paid to complete.

Good placement also prevents everyday discomfort. Centring a fan over a bed instead of the room centre pushes it too close to wardrobe doors or lights, causing a strobing shadow across the floor every time the blades spin. Placing wall fixtures without checking door swings creates collisions. Our practice catches door leaves that strike fixtures by under 50 mm before construction begins.

What this means for your plan

Check your plan to ensure every habitable room has openings on two different faces before you approve electrical points. Ask your contractor to embed all conduit, back-boxes, and fittings as the masonry rises so no walls are chased later. The tool applies these daylight geometries, clearance rules, and working heights automatically when it draws your plan. You get clear sight lines, functional task planes, and balanced light without costly structural changes on site.

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