GATE AR cheat sheet

Floor Area Ratio (FAR) = total built-up floor area ÷ plot area; permissible FAR is fixed by the local development control regulations, and the setback reduces the effective plot area used for coverage, not for FAR.

Ground coverage (%) = footprint area of building at ground level ÷ plot area × 100; FAR and coverage are independent controls, so a low coverage with tall building can still yield high FAR.

Standard human body dimensions used in design: shoulder width ≈ 450 mm, standing eye level ≈ 1500–1600 mm, comfortable single-lane stair width ≈ 900 mm, two-lane ≈ 1500 mm.

Riser–tread rule for stairs: 2R + T ≈ 600–640 mm; typical public building riser 150 mm and tread 300 mm gives 2(150)+300 = 600 mm.

Ramp gradient limits: maximum 1:12 for wheelchair users in public buildings (1:15 preferred for long ramps); landings required at every 9 m of horizontal run and at direction changes.

Daylight factor (DF) = (indoor illuminance at a point ÷ simultaneous unobstructed outdoor horizontal illuminance) × 100; overcast sky CIE standard is the reference condition for DF calculation.

Sound transmission: Sound Reduction Index R (or STC) in dB; reverberation time by Sabine's formula RT60 = 0.161 V / A, with V in m³ and total absorption A in sabins (m²·α).

Thermal comfort indices: PMV–PPD per ISO 7730; comfort zone typically 20–27 °C operative temperature with relative humidity 30–60% and air velocity below 0.2 m/s for sedentary activity.

Building height is measured from the average ground level to the top of the roof slab (or terrace parapet), not to the top of the mumty/staircase headroom in most municipal bye-laws.

Setback (front/rear/side) is measured from the plot boundary to the outermost projection of the building including balconies, and it is separate from the abutting road right-of-way width.

Fire safety: minimum two staircases for buildings above a prescribed height (commonly 24 m or as per local code), staircase width ≥ 1.5 m for high-rise, and travel distance to the nearest exit is limited by occupancy type.

Means of egress occupancy load factors: floor area per person varies by use - e.g., office ≈ 9.3 m²/person, assembly (concentrated) ≈ 0.65 m²/person; exit width is computed from occupant load × unit exit width.

Ventilation: minimum openable window area of about 1/10 of the floor area for habitable rooms; kitchen and toilet require direct or mechanical exhaust to the open air.

Universal design: minimum clear door width 900 mm, accessible WC cubicle 1500 × 1750 mm, turning circle of 1500 mm diameter for wheelchair manoeuvring.

Professional practice: architect's fee is commonly expressed as a percentage of project cost (often 4–10% depending on complexity), and the standard scope excludes supervision unless separately contracted.

Planning survey techniques: land-use survey, building condition survey, and traffic volume counts (PCU - passenger car units) form the empirical base for a master plan proposal.

Simply supported beam: maximum bending moment M = wL²/8 for UDL, and maximum shear V = wL/2; cantilever: M = wL²/2 at the support.

Deflection of a simply supported beam under UDL: δ = 5wL⁴/(384EI); the fourth-power dependence on span makes span increase far more critical than load increase.

Concrete mix designations: M20 = characteristic cube strength 20 N/mm² at 28 days; nominal mixes 1:1.5:3 (M20), 1:2:4 (M15), 1:3:6 (M10) by volume of cement:sand:coarse aggregate.

Steel: Fe415 and Fe500 denote yield strength in N/mm²; minimum clear cover for slabs is 15 mm (mild exposure) to 20 mm, and for columns 40 mm, per IS 456.

Brick masonry: standard modular brick 190 × 90 × 90 mm with 10 mm mortar joint giving 200 × 100 × 100 mm module; English bond is strongest for walls, Flemish bond is decorative.

Water supply: per capita demand for Indian cities typically 135–150 lpcd for domestic use; storage tank capacity is sized for 1–2 days of demand.

Electrical services: diversity factor reduces the total connected load to the maximum demand; power factor correction (capacitor banks) reduces kVA demand and cable sizing.

HVAC: 1 TR (ton of refrigeration) = 3.517 kW of cooling; sensible heat ratio (SHR) = sensible heat ÷ total heat, and it governs apparatus dew point selection.

Classical orders: Doric (no base, plain capital), Ionic (volute capital, base), Corinthian (acanthus capital); the Greek column height-to-diameter ratio is about 6:1 for Doric and 10:1 for Corinthian.

Indian temple architecture: Nagara style (curvilinear shikhara, no boundary wall, North India) versus Dravida style (pyramidal vimana, gopuram gateway, enclosure wall, South India).

Modern movement markers: Le Corbusier's Five Points (pilotis, free façade, open plan, ribbon windows, roof garden); Bauhaus founded 1919 by Walter Gropius; CIAM established 1928.

Vernacular climate strategies: jaali screens and courtyards in hot-dry climates for shade and evaporative cooling; steep pitched roofs in hot-humid regions for rapid rain runoff and ventilation.

Passive solar design: south-facing glazing with appropriate overhang in the northern hemisphere for winter gain; overhang depth sized so the summer sun is blocked but the lower winter sun enters.

Wind rose diagram shows the frequency and direction of prevailing winds; used to orient openings and plan natural cross-ventilation paths through the building.

Mahoney tables and bioclimatic charts are climate-analysis tools that map monthly temperature and humidity to recommend building form, shading, and ventilation strategies.

Ecological footprint and carrying capacity are planning metrics: footprint measures resource demand in global hectares, carrying capacity measures the biologically productive area available per capita.

Scale: a drawing at 1:100 means 1 unit on paper equals 100 units on site, so a 10 m wall is drawn 100 mm long; larger denominator = smaller drawing.

Orthographic projection: first-angle (Indian/European practice) places the view on the far side of the object; third-angle (US practice) places the view on the near side.

Isometric projection uses equal foreshortening on all three axes with 30° from horizontal; isometric drawing is drawn to true length, while isometric projection is scaled by 0.816.

Perspective: a one-point perspective uses one vanishing point, a two-point perspective uses two; the horizon line equals the observer's eye level, and objects below it appear from above.

Areas and volumes for site work: trapezoidal rule A = (d/2)[(a+b)/2 + sum of intermediate ordinates] and Simpson's rule for irregular plots; prismoidal formula for earthwork volumes.

Surveying: leveling by height of instrument (HI) method - HI = reduced level of benchmark + backsight; reduced level of a point = HI − foresight or intermediate sight.

Trigonometric identities frequently tested: sin²θ + cos²θ = 1, sin 2θ = 2 sin θ cos θ, and the sine rule a/sin A = b/sin B = c/sin C in a triangle.

Coordinate geometry: distance between points = √[(x₂−x₁)² + (y₂−y₁)²]; area of a polygon by the shoelace formula = ½|Σ(xᵢyᵢ₊₁ − xᵢ₊₁yᵢ)|.