Building services: plumbing, electrical and HVAC

In short

Building services are the water, waste, power, ventilation, air-conditioning, fire, gas and transport systems that make a building habitable - the "invisible" 25-40% of the project cost that an architect must plan space for at concept stage, not after. The architect sizes shafts, plant rooms, tank capacities, duct routes and toilet cores, and coordinates them with structure and finishes; detailed sizing is shared with plumbing, electrical and HVAC consultants. The governing document in India is the National Building Code of India 2016 (Part 8 Building Services, Part 9 Plumbing Services, Part 4 Fire and Life Safety), with IS codes, the Electricity Act 2003, CEA safety regulations and BEE energy codes layered on top. It is examined in B.Arch Building Services papers and in GATE-AR (services, NBC provisions, simple load and capacity calculations), and asked in every interview for architectural, MEP-coordination, project-management and green-building roles.

Explained

Scope, codes and design integration

• Services covered: water supply, drainage and sanitation, solid waste, gas supply (NBC Part 9); electrical and allied installations, lighting and ventilation, air-conditioning, lifts and escalators (NBC Part 8); fire detection and fighting (NBC Part 4).
• Key references: NBC 2016 (two volumes, with amendments); IS 2065 (water supply in buildings), IS 1742 (building drainage), IS 5329 (sanitary pipework above ground), IS 1172 (basic requirements for water supply, drainage and sanitation), IS 2470 (septic tanks), IS 732 (electrical wiring installations), IS 3043 (earthing), IS/IEC 62305 (lightning protection), IS 14665 (electric traction lifts), IS 659/660 (safety codes for air conditioning and for mechanical refrigeration). The Uniform Plumbing Code India (UPC-I, IAPMO/Indian Plumbing Association) is used by many consultants alongside the NBC.
• Statutory layer: Electricity Act 2003 and the CEA (Measures relating to Safety and Electric Supply) Regulations, 2023; state/municipal building bye-laws (which impose rainwater harvesting, solar water heating, STP and EV-charging provisions); CPCB/SPCB consent for sewage treatment and DG sets; BEE star labelling for appliances.
• Energy codes: ECSBC 2024 (Energy Conservation and Sustainable Building Code, successor to ECBC 2017) for commercial buildings with connected load of 100 kW or more (or contract demand of 120 kVA or more) and Eco Niwas Samhita for residences; States adopt them in their own versions through state rules, so confirm the State version in force before quoting clauses.
• Architect's integration tasks: stack vertical services (toilets over toilets), provide separate shafts for wet services, electrical and HVAC; fix plant locations early (UG sump, pump room, substation, DG, chiller yard, AHU rooms, terrace tanks); allow floor-to-floor height for the deepest service (usually ducts) - typically 600-900 mm of ceiling void for central AC.
• Order of priority when routing in a congested ceiling: gravity drainage (fixed slope) → large ducts → pressurised water pipes → cable trays and conduits (most flexible).

Water supply and plumbing

• Demand (NBC/IS 1172): about 135 litres per capita per day (lpcd) for residences with full flushing (roughly 90 domestic + 45 flushing); 45 lpcd for factories without bathing; hotels, hospitals, schools and offices have their own per-head figures in the NBC tables (e.g. hospitals rise with bed count).
• Sources: municipal main, borewell/tubewell, tanker; treated water (from an STP) is reused for flushing, landscape and cooling-tower make-up through a dual plumbing system in colour-coded, separately labelled pipes.
• Distribution systems:
  1. Direct supply - fixtures fed straight from the main; only where pressure and continuity are reliable.
  2. Down-take (indirect) - mains fill an underground sump, a pump lifts to an overhead tank, gravity feeds the building. The Indian default.
  3. Up-feed/boosted - pump pressurises risers directly.
  4. Hydro-pneumatic - pump with a pressure vessel and variable-speed drive maintains constant pressure; used where terrace tanks are not wanted.
• High-rise zoning: pressure at a fixture should be roughly 1-3 bar; break tanks or pressure-reducing valves every 8-12 storeys prevent excessive static head (10 m ≈ 1 bar) and fitting damage.
• Storage: sump usually 1 day's demand (more where supply is intermittent), overhead tank about one-third to half a day; fire storage is additional and non-drawable, with capacity per NBC Part 4 by occupancy and height.
• Hot water: instantaneous/storage electric geysers, gas instantaneous heaters, solar flat-plate or evacuated-tube systems (mandatory in many state bye-laws for hostels/hotels), heat-pump water heaters, central calorifier with a circulation loop in hotels and hospitals.
• Pipe materials: CPVC and PPR for hot and cold water inside buildings, uPVC for cold water, GI (declining), copper for medical gas and some hot-water work, HDPE/DI for external mains, cast iron/uPVC-SWR for waste stacks.
• Valves and protection: gate/ball valves for isolation, non-return valve at pump delivery, float valve in tanks, air-release at high points, air gap or back-flow preventer to stop cross-connection of potable and non-potable water; water hammer controlled by lower velocities (0.9-2.4 m/s), slow-closing valves and arrestors.

Drainage, sanitation and waste water

• Two drainage streams: soil (from WCs and urinals) and waste (from basins, sinks, baths); storm water is always separate from sewage.
• Systems: two-pipe (separate soil and waste stacks, each vented) - the traditional system; single-stack/one-pipe (soil and waste in one stack with a vent, or single stack with careful branch design) - standard in modern multi-storey work.
• Traps: a water seal (normally 50 mm, deeper where evaporation or siphonage is likely) blocks foul air - P, S, Q and bottle traps at fixtures; floor trap (with grating), gully trap outside the building for waste water, intercepting trap at the junction with the public sewer where required.
• Seal loss: self-siphonage (fixture's own discharge), induced siphonage (flow past the branch), back pressure, evaporation and capillary action - prevented by anti-siphonage/vent pipes, a stack vent carried above roof level, and correct branch slopes.
• Gradients: 100 mm house drain commonly 1:60, 150 mm about 1:100-1:120; design for self-cleansing velocity of at least 0.6-0.75 m/s at the expected flow; pipes are sized to run part-full (about half to two-thirds).
• External works: inspection chambers/manholes at every change of direction, gradient or diameter and at junctions, with maximum spacing commonly 30 m for shallow drains (check bye-laws); manhole depth decides whether it is a shallow, normal or deep (with steps) chamber.
• Specials: grease trap/interceptor for commercial kitchens, oil-and-petrol interceptor for car parks and workshops, pumping (ejector/sump) station for basement toilets since they are below the gravity sewer.
• On-site treatment: septic tank + soak pit/dispersion trench (IS 2470) where no sewer exists; for larger developments an STP using MBBR, SBR or MBR technology, with treated-water quality and reuse governed by CPCB/SPCB norms - most state bye-laws make an STP compulsory above a threshold plot or built-up area.
• Rainwater: roof and surface drainage sized for local rainfall intensity; rainwater harvesting (recharge pits, trenches, shafts, or storage with filtration) is mandatory in most Indian cities and is regulated for groundwater abstraction by the Central Ground Water Authority.
• Solid waste: segregated storage at source in the four streams of the Solid Waste Management Rules, 2026 (wet, dry, sanitary, special care) with a chute or ground-level bin room, sized per the NBC Part 9 Section 3 generation rates; bulk waste generators (100 kg/day or more of waste, or 40,000 L/day of water, or 20,000 m² of floor area) must process wet waste on site or buy EBWGR certificates under the SWM Rules, 2026, which superseded the 2016 Rules from 1 April 2026.

Electrical services

• Supply: 230 V single-phase (small loads) and 415 V three-phase, 50 Hz four-wire LT supply; larger buildings take HT (11 kV/33 kV) and have their own substation with transformer, HT panel, LT panel, capacitor bank, standby DG set and UPS for critical loads.
• Load estimation chain: connected load → × demand factor (per circuit/occupancy) → maximum demand → ÷ diversity across groups → contract demand in kVA. Spare capacity of 15-25% is normally allowed.
• Distribution: main LT panel → risers (cables or busbar trunking in an electrical shaft) → floor panel → distribution boards (DBs) → final circuits. Lighting, power sockets, AC and essential (DG/UPS-backed) circuits are kept on separate DBs.
• Protection devices: MCB (overload and short circuit, final circuits), MCCB (higher ratings, adjustable), RCCB/RCD (earth leakage - 30 mA for socket and wet-area circuits, 100-300 mA upstream for fire protection), ELCB, isolator, surge protection device; selectivity (discrimination) must be checked so the nearest device trips first.
• Wiring methods: PVC-insulated copper conductors in rigid/flexible conduit (concealed in walls and slabs) or casing-capping; XLPE/PVC armoured cables on trays for mains; fire-survival cables for fire pumps, lifts and alarms. Colour code: brown/black/grey phases, blue neutral, green-yellow earth.
• Earthing (IS 3043): plate, pipe or strip electrodes in a treated pit; separate earths for body (equipment) and neutral; equipotential bonding of all metal services; earth resistance kept low (commonly a few ohms, with stricter limits for substations and IT installations). Lightning protection per IS/IEC 62305 - air terminations, down conductors and earth terminations forming a mesh/cage on tall or isolated buildings.
• Allied systems the architect must plan for: fire alarm and detection (IS 2189), public address, CCTV and access control, structured data cabling, BMS, lifts and escalators (IS 14665 - machine room or MRL, pit and overhead dimensions, lobby widths, fire-evacuation and stretcher lifts per NBC Part 4), rooftop solar PV with net metering under state DISCOM regulations, and EV charging provision in parking (now required by MoP guidelines and amended bye-laws in many states).
• Power quality: capacitor banks correct power factor (DISCOM tariffs penalise low pf and reward high); harmonics from drives, LEDs and UPS need detuned capacitors or filters.

HVAC and ventilation

• Comfort basis: dry-bulb temperature, relative humidity, air movement, mean radiant temperature, clothing and activity. Indian design comfort is commonly 24-27 °C DBT with 50-60% RH for conditioned spaces; adaptive comfort models (India Model for Adaptive Comfort, used in ECBC/NBC discussion) allow wider ranges in naturally ventilated and mixed-mode buildings.
• Psychrometrics: DBT, WBT, dew point, RH, humidity ratio, enthalpy and the psychrometric chart; processes - sensible heating/cooling, humidification, dehumidification by cooling below dew point, adiabatic (evaporative) cooling, mixing. Sensible heat ratio (SHR) = sensible load / total load fixes the supply-air condition line and the apparatus dew point.
• Ventilation: natural (cross ventilation, stack effect, wind towers, courtyards, jaali) is the first choice in Indian climates; mechanical ventilation where it fails - toilets, kitchens, basements, car parks and plant rooms, sized in air changes per hour (ACH) or per-person fresh air (commonly about 8-12 L/s per person for offices, after ASHRAE 62.1/ISHRAE IAQ practice). NBC and the fire code give ACH values for toilets, kitchens and basements (basement car parks are typically ventilated at a normal rate with a higher smoke-extraction rate in fire mode) - check the current table rather than memorising a number.
• Refrigeration cycle: evaporator (absorbs room heat) → compressor → condenser (rejects heat outdoors) → expansion device → evaporator. Vapour absorption machines (LiBr-water, driven by steam, hot water or waste heat) are used where cheap heat exists.
• System types:
  • Unitary/DX: window, split, multi-split, cassette, ductable split, package unit - small to medium areas, per-room control, low capital cost.
  • VRF/VRV: one outdoor unit serving many indoor units with variable-speed compressor and refrigerant flow; excellent part-load efficiency and zoning, heat recovery possible; refrigerant piping lengths and leak detection are the constraints.
  • Central chilled water: air-cooled or water-cooled chiller (with cooling tower and condenser-water pumps) → primary/secondary chilled-water pumps → AHUs and FCUs → ducts/diffusers. Best for large buildings; needs plant room, pipe shafts and make-up water.
  • Evaporative cooling (desert coolers, direct/indirect systems) - cheap and effective only in hot-dry climates; useless in humid coastal air.
  • Radiant cooling panels/slabs with a DOAS (dedicated outdoor air system) for latent load; chilled beams; district cooling in large campuses.
• Air distribution: CAV versus VAV (VAV boxes throttle flow, fan speed falls with load - large energy saving at part load); ducts of GI sheet or pre-insulated panels, designed by equal friction, velocity reduction or static regain methods; low-side components - grilles, diffusers, dampers, VCDs, fire dampers at fire-compartment crossings, filters (pre, fine, HEPA in hospitals/cleanrooms), heat recovery wheel or plate exchanger on exhaust air.
• Load components: external (conduction through walls/roof/glass, solar gain) and internal (people, lights, equipment, infiltration, fresh air); the architect controls the biggest items through orientation, shading, glazing SHGC/U-value, insulation and WWR - good envelope design can cut installed tonnage by a third.
• Refrigerants and environment: R-22 (HCFC) is being phased out under the Montreal Protocol; R-410A, R-32 and R-290 are the common replacements, and India's HFC phase-down under the Kigali Amendment begins with a freeze later this decade and steps thereafter. Efficiency is rated by COP/EER, ISEER for room ACs under BEE star labelling (bands are revised periodically), and IPLV/NPLV for chillers.
• Heating: rarely needed in most of India; used in the Himalayan belt and in process areas - heat pumps (reverse-cycle), electric or hot-water radiators, hot-air furnaces.

Fire, gas and performance checks

• Fire services (NBC Part 4): wet riser, down-comer, yard hydrants, automatic sprinklers, first-aid hose reels, portable extinguishers (IS 2190 selection), underground static tank plus terrace tank, fire pumps with jockey pump and diesel standby, detection and alarm, public address, pressurised staircases and lift lobbies, smoke extraction - all with space and shaft implications the architect must provide.
• Gas supply (NBC Part 9 Section 4): piped natural gas (PNG) risers and meters, LPG bank or manifold rooms at ground level with natural ventilation at low level, medical gas pipelines in hospitals; no gas line in an unventilated shaft.
• Testing and commissioning: pressure/hydraulic test of water pipes, smoke or water test of drainage, insulation-resistance and earth-continuity tests for wiring, air-balancing and water-balancing reports for HVAC, flow and pressure tests of fire pumps - documented before occupancy certificate.
• Operation and maintenance: access panels, valve chambers, pump-room drainage, clearance for coil pull-out and filter change, and a BMS for monitoring; serviceability designed in, not discovered later.

Key points

• NBC 2016 - Part 9 covers plumbing services, Part 8 electrical, lighting, ventilation, AC and lifts, Part 4 fire and life safety.
• 135 lpcd - standard residential water demand (about 90 domestic + 45 flushing); other occupancies have separate NBC figures.
• Down-take system - sump + pump + overhead tank + gravity distribution; the usual Indian arrangement.
• 10 m of water ≈ 1 bar - the basis of pressure zoning, PRVs and break tanks in high-rise plumbing.
• Water seal 50 mm - the standard trap seal; lost by self/induced siphonage, back pressure, evaporation or capillarity.
• Anti-siphonage (vent) pipe - keeps trap seals intact by equalising pressure in the stack.
• Self-cleansing velocity 0.6-0.75 m/s - minimum design velocity in drains; gradients of 1:60 (100 mm) and about 1:100-1:120 (150 mm) are typical.
• Manhole - at every change of direction, gradient, diameter and at junctions; spacing per bye-laws.
• Septic tank (IS 2470) - detention volume plus sludge storage, followed by a soak pit or dispersion trench.
• Dual plumbing - separate, labelled lines for treated/recycled water used in flushing and landscape.
• Maximum demand - connected load × demand factor ÷ diversity; the figure the DISCOM contract is based on.
• RCCB 30 mA - earth-leakage protection for socket outlets and wet areas; MCB for overload/short circuit.
• IS 3043 earthing and IS/IEC 62305 lightning protection - separate body and neutral earths; equipotential bonding of all services.
• 1 TR = 3.517 kW - unit of cooling; rule of thumb for Indian offices is roughly one TR per 8-15 m² depending on envelope and loads.
• SHR - sensible/total load; decides supply air temperature and the apparatus dew point.
• VRF versus chilled water - VRF for zoned medium buildings, chilled water for large loads and long plant life.
• ECSBC 2024 / Eco Niwas Samhita - BEE energy codes for commercial and residential buildings (ECSBC succeeded ECBC 2017), adopted by States in their own versions.
• Services cost 25-40% of a building - and must be planned at concept stage, in shafts, plant rooms and ceiling voids.

Formulas and examples

Example 1 - Water demand, storage and pump for an apartment block. 60 flats × 4.5 persons = 270 persons at 135 lpcd.

• Demand = 270 × 135 = 36,450 L/day ≈ 36.5 m³/day (about 24.3 m³ domestic + 12.2 m³ flushing).
• Underground sump = 1 day ≈ 36,000 L; overhead tank = one-third day = 12,150 → provide 12,000 L (split into two compartments for cleaning). Fire storage is added separately per NBC Part 4.
• Pump to fill the OH tank in 20 min: Q = 12,000/20 = 600 L/min = 10 L/s = 0.01 m³/s. Static lift 30 m + friction 5 m = H = 35 m.
• Hydraulic power = 1,000 × 9.81 × 0.01 × 35 = 3,434 W ≈ 3.43 kW. With η_pump = 0.60: shaft power = 5.72 kW; with η_motor = 0.85: input = 6.73 kW → select a 7.5 kW (10 hp) pump set, with a 100% standby.

Example 2 - Drain capacity and self-cleansing check. 100 mm uPVC drain at 1:60, n = 0.013.

• Full bore: A = π(0.1)²/4 = 0.007854 m², R = D/4 = 0.025 m, S = 0.01667.
• V = (1/0.013) × 0.025^2/3 × 0.01667^1/2 = 76.92 × 0.0855 × 0.1291 = 0.85 m/s (> 0.6 m/s, self-cleansing ✓).
• Q_full = 0.85 × 0.007854 = 0.00667 m³/s = 6.7 L/s; running half full the velocity is the same (R is unchanged) and Q ≈ 3.3 L/s - adequate for a small block's soil branch.

Example 3 - Septic tank and rainwater harvesting. 20 users, q = 100 L/day, detention 1 day, sludge 30 L/person/year, desludged every 2 years.

• Volume = (20 × 100 × 1) + (20 × 30 × 2) = 2,000 + 1,200 = 3,200 L = 3.2 m³.
• At 1.5 m liquid depth, area = 2.13 m² → about 2.0 m × 1.1 m liquid plan, plus 0.3 m free board; IS 2470 Part 1 also gives ready tables.
• Terrace 500 m², annual rainfall 800 mm, C = 0.85 → V = 0.85 × 0.8 × 500 = 340 m³/year harvestable, i.e. about 9 days of the Example 1 demand - normally used for recharge rather than storage.

Example 4 - Electrical load, cable drop and power factor. A floor panel feeds 50 kW at 0.85 pf on 415 V, 3-phase, 60 m away on 50 mm² copper (R ≈ 0.45 Ω/km, X ≈ 0.08 Ω/km at operating temperature).

• Current I = 50,000 / (1.732 × 415 × 0.85) = 50,000 / 611 = 81.8 A → choose a 100 A MCCB and a cable with ≥ 100 A derated capacity.
• ΔV = 1.732 × 81.8 × (0.45 × 0.85 + 0.08 × 0.527) × 0.06 = 141.7 × 0.4247 × 0.06 = 3.6 V = 0.87% of 415 V - well within the 3% guideline.
• Correcting pf from 0.85 to 0.95: kVAr = 50 × (0.6197 − 0.3287) = 14.6 kVAr → install a 15 kVAr bank; apparent power falls from 58.8 kVA to 52.6 kVA, cutting the contract demand and the low-pf penalty.

Example 5 - Cooling load, tonnage and air flow for an office room. Sensible load 10 kW, latent 2.5 kW, 15 occupants.

• Total = 12.5 kW → TR = 12.5/3.517 = 3.55 TR → select a 4 TR ductable unit (or 3.5 TR with load review). SHR = 10/12.5 = 0.80.
• Supply air at ΔT = 11 K: V = 10/(1.2 × 11) = 0.758 m³/s = 758 L/s ≈ 1,606 CFM.
• Fresh air at 10 L/s per person = 150 L/s, about 20% of supply air.
• Room 100 m² × 3 m = 300 m³ → ACH = (0.758 × 3,600)/300 = 9.1 ACH.
• If served from a central plant instead: 100 TR block load = 351.7 kW; chilled water at ΔT = 5 K → ṁ = 351.7/(4.187 × 5) = 16.8 L/s ≈ 60.5 m³/h.

Where it is used

• Architectural practice and MEP consultancies (Voyants, AECOM India, WSP India, Spectral, Jacobs) - shaft and plant-room planning, services coordination drawings, NBC and bye-law compliance submissions.
• Real-estate and infrastructure developers (DLF, Godrej Properties, Prestige, Brigade, Lodha, L&T Construction) - services BOQs, tonnage and load budgets, value engineering of HVAC and plumbing packages.
• Green-building and energy roles - IGBC, GRIHA and LEED assessments, ECBC compliance, water-balance and STP-reuse calculations, solar water heating and rooftop PV integration.
• Government and institutional work - CPWD and PWD service specifications, Smart Cities and AMRUT water-supply and sewerage projects, hospital and airport projects where medical gas, filtration and redundancy drive the design.
• Product and contracting side - Blue Star, Voltas, Daikin, Carrier, Kirloskar and Grundfos pumps, Jaquar/Hindware/Supreme/Astral plumbing products, Havells/Legrand/Schneider/L&T electrical switchgear - application engineering and sales roles.
• Facility management and BMS operations - commissioning, air and water balancing, energy audits, retrofit of chillers, pumps and lighting controls in existing buildings.

Interview questions

• Q: What per-capita water demand do you design residences for in India, and how is it split? A: About 135 lpcd per NBC/IS 1172 - roughly 90 lpcd domestic and 45 lpcd flushing, which lets a dual plumbing system feed flushing from treated water.
• Q: Why is the down-take system preferred in Indian buildings? A: Municipal supply is intermittent and at low pressure, so water is stored in a sump, pumped once to an overhead tank, and gravity-fed - giving continuous supply and steady pressure with one pumping cycle.
• Q: What is an anti-siphonage pipe and why is it needed? A: A vent connected near the trap that equalises air pressure in the stack, preventing self- and induced siphonage from sucking out the 50 mm water seal and letting foul gas into the room.
• Q: One-pipe or two-pipe drainage - which would you use in a 15-storey apartment and why? A: A single-stack/one-pipe system with proper venting; it uses fewer stacks and less shaft space, and modern pipe sizing and branch geometry keep seals safe.
• Q: Why must self-cleansing velocity be maintained in a drain? A: Below about 0.6-0.75 m/s solids settle and the drain silts up and blocks; the gradient is therefore chosen for the expected flow, not made as flat as possible.
• Q: Where would you locate manholes? A: At every change of direction, gradient or pipe diameter, at junctions, and at intervals set by the bye-laws (commonly up to about 30 m for shallow drains) so every length can be rodded.
• Q: Difference between MCB, MCCB and RCCB? A: MCB and MCCB protect against overload and short circuit (MCCB at higher, adjustable ratings); RCCB detects earth-leakage current - 30 mA for socket and wet-area circuits - and protects people, not cables.
• Q: Why are body earthing and neutral earthing kept separate? A: The neutral earth carries system return/unbalance current, while the body earth must stay at zero potential to clear faults safely; mixing them puts fault current on equipment enclosures.
• Q: What is one tonne of refrigeration and how do you estimate tonnage quickly? A: 3.517 kW of heat removal - the rate that freezes a short ton of water in 24 hours; a quick Indian office estimate is one TR per 8-15 m², refined by a proper load calculation.
• Q: VRF versus central chilled water - how do you choose? A: VRF suits mid-sized buildings with varied occupancy because of excellent part-load efficiency and zoning; chilled water wins above roughly 100-150 TR on efficiency per TR, plant life and capacity, if plant-room space and operators are available.
• Q: How does an architect reduce the HVAC load before the consultant sizes it? A: Orientation, shading and reduced window-to-wall ratio, low-SHGC glazing, insulated roof and walls, lighter internal gains and good daylight - envelope decisions typically cut installed tonnage substantially.
• Q: Why is a fire damper placed where a duct crosses a fire wall? A: The duct would otherwise breach the compartment; the damper closes on heat or alarm signal and restores the wall's fire rating, as required under NBC Part 4.

Common mistakes

• Treating services as an afterthought - no shafts, no plant room, insufficient ceiling void - and then cutting beams or dropping ceilings to fit ducts.
• Quoting 135 lpcd for every occupancy; offices, hospitals, hotels and schools have their own NBC figures, and fire storage is an addition that cannot be drawn for domestic use.
• Forgetting friction loss and residual pressure when computing pump head, or ignoring pump and motor efficiency, so the motor is undersized.
• Mixing units: L/s with m³/h, kW with TR, lpcd with m³/day, mm² cable with current rating - and comparing TR directly with electrical kW input.
• Stacking toilets without vertical alignment, or putting a soil stack in a dry shaft with electrical cables.
• Over-flattening drain gradients to save depth (silting) or over-steepening them (water races ahead of solids).
• Sizing air-conditioning by floor area alone for a glazed, west-facing or high-occupancy space, and ignoring fresh-air and latent loads - which is why humidity complaints follow "correctly sized" systems.

Related topics

Building construction · Building materials: cement, aggregates and bricks · Acoustics and lighting · Climatology and passive design · Green buildings, IGBC/GRIHA and ECBC · Building bye-laws, NBC and professional practice