LESSON 2.2 — Building Construction Techniques

A. Standard Map

Topic	Governing Source	Exam Focus
Load-bearing vs framed construction	NBC 2016 Part 6; IS:1905:2002	Selection logic; height and span limits
Foundation types	IS:6403:1981 (shallow); IS:2911:1979 (piles)	Selection by soil and load; pile types
Masonry bond types	IS:2212:1991 — Code of Practice for Brickwork	English, Flemish, Stretcher — arrangement rules
RCC construction sequence	IS:456:2000; IS:2505 (concrete vibrators)	Pour sequence; curing period
Roof systems	NBC 2016 Part 6; standard construction practice	Type identification by shape and construction
Stairs — dimensional standards	NBC 2016 Part 4; IS:1948	Rise–going rule (2R+G); type identification
Modular coordination	IS:1628:1974; NBC 2016 Part 3	Basic module 100 mm; preferred dimensions

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B. Why It’s Used

Construction technique questions test whether a candidate understands how buildings are physically assembled — not just what materials are used but how they are put together and in what sequence. GATE AR regularly tests masonry bond types (Flemish vs English), foundation selection logic, and stair dimensioning. UPSC-CPWD has heavy weightage on masonry and RCC construction. The 2R+G formula and curing period distinctions are among the most reliably tested parameters across all exam years.

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C. Mechanism in Words

1. A structural scheme begins with the decision of how vertical loads are carried: by thick walls (load-bearing) or by a separate skeletal frame (framed).
2. Loads from the superstructure flow down to the ground through the foundation; the foundation type is matched to the soil bearing capacity and the magnitude of the load.
3. Masonry is laid in specific patterns (bonds) that interlock bricks across wall thickness — bond geometry determines structural efficiency.
4. In RCC construction, formwork holds wet concrete in shape; reinforcement carries tension; concrete carries compression; the two work together after the concrete hardens and formwork is removed.
5. The roof seals the building envelope — its form determines drainage, structural span, and load distribution.
6. Stairs connect floor levels; their dimensional geometry must satisfy comfort (2R+G formula) and code minima for width, rise, and going.

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D. Core Concept Explanations

C1. Load-Bearing vs Framed Construction

Property	Load-Bearing Masonry	Framed Construction (RCC/Steel)
Load path	Loads carried by walls → foundation	Loads carried by columns and beams → foundation
Wall material	Brick, stone, or block masonry (structural)	Walls are non-structural infill (partition) panels
Floor/roof span	Limited by wall spacing (up to ~4–5 m economically)	Beams bridge between columns; span up to 6–12 m+ economically
Height limit	Generally ≤ 3 storeys (IS:1905)	Effectively unlimited with appropriate column design
Opening limitation	Openings weaken walls; lintel over every opening required	No restriction — partitions independent of structure
Economy	Economical for small residential (<3 storeys, <5 m span)	Economical for medium-to-large buildings
Seismic behaviour	Poor ductility; poor in seismic zones III–V	Better ductility with IS:13920 detailing

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C2. Foundation Types — Selection Logic

Foundation Type	Mechanism	Best For	Selection Criterion
Strip footing	Continuous strip of concrete beneath a load-bearing wall	Load-bearing masonry buildings; moderate loads	Good soil bearing capacity; loads distributed along a wall
Isolated (pad) footing	Individual rectangular or square pad under each column	Framed buildings; columns with well-spaced loads	Firm soil; columns spaced ≥ 2–3 m apart
Combined footing	Single footing supporting two or more columns	Columns too close together for individual footings; property line constraint	Closely spaced columns; one column near boundary
Raft (mat) foundation	Single slab covering the entire building footprint	Weak soil (low bearing capacity); heavy loads; basement structures	Bearing capacity too low for individual footings
Pile foundation	Long slender shafts transferring load to deeper strata	Soft soil near surface; heavy loads; where shallow founding is impossible	Soft/compressible surface layer; waterlogged sites; high column loads

Pile types:

Pile Type	Load Transfer	Example
Friction pile	Load transferred primarily through skin friction along pile shaft	Soft clay sites where hard stratum is very deep
End-bearing pile	Load transferred to hard stratum at pile tip	Soft surface layer over dense gravel, rock, or dense sand
Bored cast-in-situ pile	Hole bored, reinforcement cage placed, concrete poured in situ	Where vibration is unacceptable (near existing structures)
Driven precast pile	Precast pile driven by hammer	Where bored piling is impractical; sandy or gravelly soils

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C3. Masonry Bond Types (IS:2212:1991)

Bond	Course Arrangement	Min. Wall Thickness	Key Property
English Bond	Alternate courses: one course ALL headers, next course ALL stretchers; quoin closer next to corner header	One brick (200 mm)	Strongest structural bond — no continuous vertical joints; max transverse bond
Flemish Bond	Each course has ALTERNATING headers and stretchers; every course begins with quoin closer	One brick (200 mm)	Better appearance than English Bond; slightly less strength due to some vertical joint alignment
Stretcher Bond (Running Bond)	All courses = stretchers only; each course offset by half brick	Half brick (100 mm)	Suitable ONLY for half-brick thick partition walls or cavity wall inner leaves; cannot be load-bearing on its own
Rat Trap Bond	Bricks placed on edge (vertical), creating internal cavity	One brick (200 mm)	~25% less brick+mortar; internal air cavity = thermal insulation; surface appearance like Flemish Bond

Mortar proportions:

Mortar Mix (Cement:Sand)	Application
1:3	High-strength masonry; plinth level and below DPC; parapet walls
1:4	Load-bearing masonry above plinth; sills and copings
1:6	General non-load-bearing internal masonry
1:8	Filling, backing of thick walls; low-strength work

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C4. RCC Construction Sequence

1. Set up formwork: Shutters for columns, walls, beams, and slabs erected and aligned.
2. Steel placement: Reinforcement bars cut, bent, and placed per bar bending schedule; cover blocks placed to maintain specified cover.
3. Inspection: Cover, laps, and bar diameters verified before concreting.
4. Concrete mixing and placement: Concrete mixed at design w/c ratio; placed in layers ≤ 300 mm; not dropped from height > 1.5 m to prevent segregation.
5. Compaction: Needle vibrator or table vibrator used; vibrator not placed directly on reinforcement; vibrated at ~450 mm intervals; immersion time ~15 seconds per position.
6. Curing: Concrete protected from drying for minimum 7 days (OPC) or 14 days (PPC/slag cement); methods include ponding, wet burlap, curing compound.
7. Formwork removal (striking): Minimum periods per IS:456 — column/wall sides = 24–48 hours; beam/slab soffits = 14–21 days.

Cover requirements (IS:456, Clause 26.4):

Member	Minimum cover to main reinforcement	Severe exposure
Slab	20 mm	30 mm
Beam	25 mm	35 mm
Column	40 mm	50 mm
Foundation	50 mm	—

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C5. Roof Systems

Roof Type	Form	Structural Principle	Application
Flat roof	Horizontal or near-horizontal slab	RCC slab spanning between beams/columns; waterproofing layer essential	Most common urban building type; allows roof terrace
Pitched roof	Sloped triangular form	Rafter-purlin-truss system; slope sheds rainwater; suited for high rainfall regions	Residential bungalows; industrial sheds
Shed/mono-pitch	One sloped plane	Simple rafter system	Industrial buildings; ancillary structures
Shell roof	Doubly curved thin concrete surface	Compression-dominant; self-stiffening through curvature	Long-span structures; auditoriums; warehouses
Folded plate	Flat slabs folded into angular profile	Thin concrete gains stiffness through folding	Medium-span roofs; can span 20–30 m
Space frame	3D triangulated steel network	Spread loads triaxially; very efficient material use	Long-span column-free halls; airports; stadia

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C6. Stair Types and Dimensional Standards

Stair types (by geometry):

Type	Description	Use
Dog-leg stair	Two parallel flights connected by a half-landing; flights go in opposite directions	Most common in residential and commercial buildings; space-efficient
Open newel stair	Similar to dog-leg but with a gap (well) between flights; decorative newel post	Institutional buildings; wider landings
Spiral stair	Circular plan; single column (newel) at centre	Emergency egress; space-constrained access; not primary escape route
Scissor stair	Two interleaved dog-leg stairs sharing the same footprint	Fire-escape arrangements; minimises area per stair
Flying stair	No visible support; stairs appear to project from wall only	Feature staircases in public buildings

2R + G dimensional rule:

Variable	Definition	Code Limit	Comfort Range
R (Riser)	Vertical height of one step	R ≤ 190 mm (NBC 2016)	150–175 mm (preferred)
G (Going/Tread)	Horizontal depth of one step (nosing to nosing)	G ≥ 250 mm (NBC 2016)	250–300 mm
2R + G	Comfort check formula	—	600–650 mm

Worked check:
R = 175 mm, G = 280 mm → 2(175) + 280 = 350 + 280 = 630 mm ✓ (within 600–650 mm)

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C7. Modular Coordination (IS:1628:1974)

Basic Module (M) = 100 mm. All building component dimensions should be multiples of 100 mm.

Level	Increment	Use
Basic module	100 mm (1M)	Component dimensions: bricks, blocks, tiles, panels
Multimodule	300 mm (3M)	Room dimensions; structural grid spacing for small buildings
Multimodule	600 mm (6M)	Bay dimensions; structural grids for medium buildings
Multimodule	1200 mm (12M)	Structural grids for large buildings; planning grids

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E. Design/Parameter Table

Parameter	Value	Unit	Source
Load-bearing masonry max height (IS:1905)	≤ 3 storeys	storeys	IS:1905:2002
Basic module	100	mm	IS:1628:1974
Max. riser height	190	mm	NBC 2016 Part 4
Min. going (tread)	250	mm	NBC 2016 Part 4
2R + G comfort range	600–650	mm	NBC 2016
Min. OPC curing period	7	days	IS:456 Cl. 21
Min. PPC/slag curing period	14	days	IS:456 Cl. 21
Concrete layer thickness (max pour)	300	mm	IS:456 Cl. 13
Max height of concrete drop (segregation)	1500	mm	IS:456 Cl. 13
Vibrator immersion time (approx.)	~15	seconds	IS:456 Cl. 13
Vibrator spacing	~450	mm	IS:456
Column/wall side formwork — min. removal	24–48	hours	IS:456 Cl. 11
Beam/slab soffit formwork — min. removal	14–21	days	IS:456 Cl. 11
Slab minimum cover	20	mm	IS:456 Cl. 26.4
Column minimum cover	40	mm	IS:456 Cl. 26.4
Foundation minimum cover	50	mm	IS:456 Cl. 26.4

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F. Design Criteria

Decision	Governing Criterion	Code
Foundation type	Soil bearing capacity; column spacing; load magnitude	IS:6403; IS:2911
Masonry bond selection	Wall thickness required; structural vs appearance priority	IS:2212:1991; IS:1905
Load-bearing vs framed	Number of storeys; span requirements; seismic zone	IS:1905; IS:13920
Stair dimensions	2R+G comfort check; R ≤ 190 mm; G ≥ 250 mm	NBC 2016 Part 4
Curing period	Cement type (OPC vs PPC); member type	IS:456 Cl. 21
Concrete cover	Exposure condition; member type	IS:456 Cl. 26.4

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Code Comparisons

Code	Governs	Key Limit
IS:1905:2002	Load-bearing masonry	≤ 3 storeys; seismic zone reinforcement requirements
IS:2212:1991	Masonry bond types	English, Flemish, Stretcher, Rat Trap definitions
IS:6403:1981	Shallow foundations	Bearing capacity for strip / pad / raft
IS:2911 Pt 1/Sec 2:1979	Pile foundations	Bored cast-in-situ pile design
IS:456:2000	RCC construction	Curing (Cl. 21); formwork removal (Cl. 11); cover (Cl. 26.4)
IS:1628:1974	Modular coordination	Basic module = 100 mm; multimodules 300 / 600 / 1200 mm
NBC 2016 Part 4	Stair dimensions	R ≤ 190 mm; G ≥ 250 mm; 2R+G = 600–650 mm

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G. Application Zones

Element	Construction Technique	Selection Reason
Low-rise residential (≤ 3 storeys)	Load-bearing masonry; strip footing	Economical; structural demands manageable with masonry
Multi-storey frame (4+ storeys)	Framed RCC or steel; isolated/raft/pile foundation	Gravity + lateral loads require frame ductility
Partition walls	Stretcher bond (half-brick, 100 mm)	No structural role; partition only — no headers needed
Exposed structural masonry	English Bond (full-brick, 200 mm)	Maximum transverse bond; no continuous vertical joints
Decorative facades	Flemish Bond	Better appearance than English Bond
Columns near property line	Combined footing	Prevents eccentric loading from boundary constraint
Waterlogged / soft-soil site	Raft or pile foundation	Low bearing capacity; settlement control critical
Deep soft layer over hard stratum	Pile foundation (end-bearing)	Bypasses weak surface layer; load transferred to hard stratum

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H. Common Confusions

Confusion	Correct Distinction
Dog-leg vs open newel stair	Dog-leg has NO gap between flights; open newel has a gap (well) and is decorative. Both have two flights reversing direction at a landing.
English Bond vs Flemish Bond	English Bond = alternating WHOLE COURSES of headers and stretchers. Flemish Bond = headers and stretchers WITHIN THE SAME COURSE alternating. Visual clue: English shows bands; Flemish shows a regular mixed pattern in every course.
Stretcher Bond load-bearing use	Stretcher Bond is for HALF-BRICK partitions only — it cannot be used as a load-bearing wall because there are no headers tying across the wall thickness.
2R + G = a formula to find G	It is a COMFORT VERIFICATION check. G and R are each independently constrained by code limits (R ≤ 190, G ≥ 250). The check verifies that the chosen combination is comfortable.
Curing period OPC vs PPC	OPC = 7 days minimum. PPC (Portland Pozzolana Cement) and slag cement = 14 days minimum. PPC hydrates slower; shorter curing produces weaker concrete.
Raft foundation vs pile foundation	Raft spreads load over a wide area at shallow depth. Pile transfers load to deep strata. Both used for weak surface soils but for different reasons — raft works when bearing capacity is low but sufficient with a larger area; piles when even a raft would be inadequate or settlement would be unacceptable.

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I. Compare & Contrast

Pair	Item 1	Item 2	Key Difference
Masonry systems	Load-bearing	Framed	Load-bearing: walls are structural (≤ 3 floors); Framed: walls are infill (unlimited floors with appropriate design)
Bond types	English Bond	Flemish Bond	English: whole courses alternate (H course, then S course) — strongest; Flemish: H+S within every course — better appearance
Pile types	Friction pile	End-bearing pile	Friction: load via skin friction (deep soft clay); End-bearing: load transferred at hard stratum tip
Curing	OPC 7 days	PPC 14 days	PPC hydrates slower → needs longer curing → weaker if cured only 7 days
Foundations	Raft	Pile	Raft: spreads at shallow depth (low but workable bearing capacity); Pile: bypasses weak surface entirely
Stair types	Dog-leg	Open newel	Dog-leg: no gap between flights; Open newel: has a well (gap) with decorative newel — both reverse direction at landing

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J. Memory Hooks

• English = Entire courses alternate: EN-glish → EN-tire courses of headers, then stretchers
• Flemish = Fancy mixed in every course: every course has H-S-H-S pattern
• Stretcher = partition only, 100 mm: “Stretch a partition, not a wall”
• OPC 7 days, PPC 14 days: “PPC = Please Pour Concrete more time”
• 2R + G = 600–650 mm: two risers + one going = one comfortable stride
• Foundation select mnemonic: Firm → Strip | Close columns → Combined | Weak soil → Raft | Deep soft layer → Pile
• Basic module = 100 mm: “One hundred millimetres — one and only module”

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K. Revision Ladder

Level	Task	Test Yourself
L1 — Recall	State: English vs Flemish bond difference; OPC vs PPC curing days; minimum stair dimensions (R and G); basic module value	Describe English Bond vs Flemish Bond in two sentences each without notes
L2 — Apply	Calculate number of risers for 3000 mm floor-to-floor height with R = 175 mm; verify 2R+G comfort; select foundation type for given soil scenario	Work through Mini-Check I questions without looking at answers
L3 — Analyse	Justify foundation selection for a waterlogged clayey site with heavy column loads; explain why load-bearing masonry is limited to 3 storeys structurally; compare seismic behaviour of masonry vs RCC frame	Design a stair for 2800 mm floor-to-floor: find R, G, check 2R+G, verify against code

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L. Exam Traps

Trap	Incorrect Assumption	Correct Answer
T07	“Flemish Bond is stronger than English Bond”	English Bond is structurally stronger — no continuous vertical joints; better transverse bond. Flemish Bond is more attractive but slightly weaker.
T08	“Stretcher Bond can be used for load-bearing walls”	Stretcher Bond is for half-brick partitions ONLY — no headers cross the wall thickness; cannot carry transverse loads or act structurally.
T09	“Minimum curing period is 14 days for all concrete”	14 days is for PPC/slag cement. For OPC, minimum is 7 days. The 14-day figure applies to pozzolanic/blended cements which hydrate more slowly.
T10	“Vibrator should be placed on the reinforcement bars”	Placing the vibrator directly on bars causes segregation and can displace bars. The vibrator must be inserted into the concrete between bars.
T11	“Basic module in India = 300 mm”	Basic module = 100 mm (IS:1628:1974). 300 mm is a multimodule (3M); 1200 mm is the planning grid (12M).
T12	“Column/wall formwork must remain for 14 days before striking”	Column/wall SIDE formwork (not soffit) can be struck after 24–48 hours as these faces are not load-bearing formwork — the slab/beam soffit must wait 14–21 days.

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M. Answer-Writing Cues

For bond-type identification:

For foundation selection:

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N. PYQ Integration (2007–2026 verified)

Topic	Exam Appearance	Question Pattern
English Bond vs Flemish Bond	GATE, UPSC-CPWD, state PSC multiple years	MCQ: describe a bond; identify it; OR identify from image description
Stretcher Bond limitation	GATE	MCQ: “Stretcher bond is used for walls of minimum thickness…”
2R + G formula	GATE multiple years	MCQ: given R and G, check if combination is satisfactory; NAT possible
Minimum curing period	GATE, UPSC-CPWD	MCQ: OPC vs PPC distinction; 7 vs 14 days
Foundation type selection	UPSC-CPWD, state PSC	MCQ: match soil condition/load scenario to foundation type
Basic module	GATE, UPSC-CPWD	MCQ: “India’s basic module for modular coordination is…”
A 230 mm thick brick wall of 10 m length and 3 m height is built using a Flemish bond…	GATE AR 2022 Q47	NAT: Ans: 3400–3500 bricks
The reflected ceiling plan and section of a reinforced cement concrete roof are shown in…	GATE AR 2022 Q48	NAT: Ans: 24.50–25.30 m³
Match the items in Group-I with the corresponding items in Group-II.	GATE AR 2025 Q57	MCQ: Ans: (A)
The section of a R.C.C. staircase flight is shown in the figure below. Each riser and…	GATE AR 2026 Q44	NAT: Ans: 42
Setting out of the foundation is a process executed	GATE AR 2026 Q52	MCQ: Ans: (C)
The different parts of a parapet wall and terrace section are labelled as P, Q, R, S, T…	GATE AR 2026 Q61	MSQ: Ans: (A)(B)(D)

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O. Mini-Check — Lesson 2.2 (5 Questions)

Q1 (MCQ): A masonry wall is constructed such that every course contains alternating headers and stretchers, with every course beginning with a quoin closer adjacent to the corner header. This describes:
(A) English Bond (B) Flemish Bond (C) Stretcher Bond (D) Rat Trap Bond

A1: (B) Flemish Bond. The key identifier: headers and stretchers WITHIN THE SAME COURSE. English Bond would have whole courses alternating — one course all headers, next all stretchers.

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Q2 (MCQ): A staircase has a riser (R) = 160 mm and a going (G) = 290 mm. Is this combination acceptable per NBC 2016?
(A) No — riser exceeds maximum (B) No — 2R + G falls outside comfort range (C) Yes — both code limits satisfied; 2R + G = 610 mm ✓ (D) No — going is below minimum

A2: (C) Yes. R = 160 mm ≤ 190 mm ✓; G = 290 mm ≥ 250 mm ✓; 2R + G = 2(160) + 290 = 320 + 290 = 610 mm → within 600–650 mm ✓. All conditions satisfied.

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Q3 (MCQ): Per IS:456:2000, what is the minimum period of water curing required for structural RCC made with Portland Pozzolana Cement (PPC)?
(A) 3 days (B) 7 days (C) 14 days (D) 28 days

A3: (C) 14 days. PPC (pozzolanic/blended cement) hydrates more slowly than OPC. IS:456 requires a minimum of 14 days for PPC, slag cement, and other blended cements. OPC requires 7 days.

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Q4 (MCQ): Stretcher Bond (Running Bond) is suitable only for masonry walls of minimum thickness:
(A) 200 mm (one brick) (B) 150 mm (C) 100 mm (half brick) (D) 300 mm

A4: (C) 100 mm (half brick). Stretcher Bond uses only stretchers in every course — no headers cross the wall thickness. It is therefore suitable only for half-brick (100 mm) partition walls. Load-bearing walls require at least English or Flemish Bond (one full brick = 200 mm).

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Q5 (NAT): The staircase in a residential building has a total floor-to-floor height of 3000 mm and a going (tread) of 275 mm. Using the 2R + G formula with a target value of 625 mm, find the required riser height (R). How many risers are in the flight? (Answer: riser height in mm; number of risers as integer.)

A5:
– From 2R + G = 625 → 2R = 625 − 275 = 350 → R = 175 mm
– Check: R = 175 mm ≤ 190 mm ✓; G = 275 mm ≥ 250 mm ✓; 2R + G = 350 + 275 = 625 ✓
– Number of risers = 3000 ÷ 175 = 17.14 → 18 risers (round up; each step slightly under 175 mm)
– Actual riser = 3000 / 18 = 166.7 mm — recheck 2R + G = 2(166.7) + 275 = 333.4 + 275 = 608 mm ✓

Riser: 175 mm (target) / 166.7 mm (actual with 18 risers); Risers: 18

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