ITI/NCVT Mason Building Constructor (AITT Theory) cheat sheet

Fall protection is required at heights of 1.8 m or more; guardrails consist of a top rail at 1.0 m, a mid rail at 0.5 m and a 150 mm toe board.

A scaffold platform must be at least 450 mm wide when used for men and materials, fully planked with no gap greater than 25 mm.

Excavations deeper than 1.5 m require shoring, benching or battering; inspection by a competent person is required before each shift.

Safe manual lifting limit for one worker is about 20 kg at waist height; heavier loads need two persons or mechanical aid.

Ladder inclination is 1 in 4 (about 75 degrees); the ladder must extend 1.0 m above the landing platform.

Silica dust from cutting concrete or bricks requires wet cutting or local exhaust ventilation plus a P2/P3 respirator.

Portland cement is alkaline (pH about 12-13); eye contact requires immediate flushing with clean water for at least 15 minutes.

Electrical tools on site operate at 230 V single phase; use 110 V CTE or RCD-protected supply in wet or confined conditions.

Standard burnt clay brick: 190 x 90 x 90 mm modular or 230 x 110 x 70 mm traditional; water absorption should not exceed 20 percent by mass.

Brick compressive strength classes run from 3.5 to 35 N/mm2; a first-class brick gives not less than 10 N/mm2 and has a sharp, ringing sound.

Ordinary Portland cement 33/43/53 grade denotes 28-day compressive strength in N/mm2 of a 1:3 mortar cube.

Cement should be stored on a dry platform, stacked not more than 8 bags high, and used within 3 months of manufacture.

Sand for mortar is fine aggregate passing a 4.75 mm sieve; silt and clay content should not exceed 5 percent for good bond.

Aggregate for concrete: fine 4.75 mm and below, coarse 20 mm nominal for normal RCC work, 40 mm for mass concrete.

Lime for mortar is slaked quicklime; hydraulic lime sets under water, fat lime requires air and hardens by carbonation.

Water for concrete and mortar must be clean and free of oil, acid, alkali and organic matter; potable water is acceptable.

A trowel blade is typically 250-300 mm long; the brick trowel lays mortar, the pointing trowel (about 150 mm) finishes joints.

A 600 mm spirit level reads the bubble between lines for level; a plumb bob or plumb rule transfers verticality over 1.5-2 m.

A mason's square checks 90-degree corners; the 3-4-5 method (or multiples) sets out a right angle on the ground.

A bolster and club hammer cut bricks and blocks; a cold chisel cuts mortar joints during repair and chasing.

A hawk holds mortar while the trowel picks it up; a mortar board is the flat working surface on the scaffold.

A jointer or pointing tool forms weather-struck or bucket-handle joints; a raking tool removes mortar for pointing depth.

A line and pins stretched between profiles controls courses; line blocks keep the line taut and offset from the face.

A concrete mixer drum capacity is quoted in litres of mixed output; a half-bag mixer is about 100-120 litres per batch.

Stretcher bond: all bricks laid as stretchers, half-brick overlap, used for half-brick (115 mm) walls and cavity leaves.

English bond alternates a header course and a stretcher course; strongest traditional bond, no continuous vertical joint.

Flemish bond alternates stretcher and header in every course; more decorative than English bond but weaker in compression.

Header bond uses headers only with three-quarter bats at corners; used for curved work and footings of one-brick walls.

English garden wall bond has three stretcher courses to one header course; economical for one-brick walls.

Quetta bond uses bricks on edge with voids filled by concrete; used for 350 mm and thicker walls in seismic areas.

Raking bond (herringbone or diagonal) is used to bond facing to backing and to distribute load in thick walls.

Rule for bonding: vertical joints in alternate courses must not align; minimum lap is one-quarter brick (about 57 mm).

AAC block density is about 550-650 kg/m3 against 1800-2000 kg/m3 for burnt clay brick, reducing dead load.

AAC blocks absorb water readily; use a thin-bed adhesive mortar of 2-3 mm rather than a 10 mm cement mortar joint.

A brick wall should be raised not more than 1.0-1.5 m in a day to avoid mortar squeeze-out and loss of plumb.

Wetting of bricks before laying is required for dry, porous bricks so mortar water is not absorbed; do not soak.

Quoins are the corner bricks; toothing is the stepped end of a wall left for future bonding, one-quarter brick per course.

Cavity wall: two leaves of 100 mm separated by a 50-75 mm cavity, tied with wall ties at 450 mm vertical and 900 mm horizontal.

Wall ties in a cavity must slope slightly outward and downward so any water drains to the outer leaf.

Reinforcement: horizontal ladder or truss mesh in bed joints at 400-600 mm vertical spacing controls shrinkage cracking.

Mortar grades: M (1:3), S (1:4), N (1:6), O (1:8) cement:sand by volume; higher cement gives higher strength and lower workability.

Mortar cube strength at 28 days: 1:3 cement mortar about 10 N/mm2, 1:6 about 5 N/mm2, 1:8 about 3 N/mm2.

Lime or plasticiser is added to improve workability and water retention; over-plasticising reduces bond strength.

Mortar should be used within 2 hours of mixing in hot weather and within 3 hours in cool weather; never re-temper.

Fat mortar is rich in lime and buttery; lean mortar is sandy and harsh; the correct mix is workable but not sticky.

Mortar joint thickness for brickwork is 10 mm; for thin-bed blockwork 2-3 mm with adhesive.

Water retentivity is the ability of mortar to retain water against suction of the masonry unit; low retention causes poor bond.

For repointing, use a mortar weaker than the original masonry so the joint, not the brick, absorbs movement.

Nominal concrete mixes: 1:3:6 (M10), 1:2:4 (M15), 1:1.5:3 (M20); water-cement ratio typically 0.45-0.55 by mass.

Concrete cube strength at 28 days is the design criterion; M20 means 20 N/mm2 characteristic cube strength.

Slump test measures workability: 25-75 mm for normal RCC, 75-125 mm for pumped or heavily reinforced sections.

Compaction by needle vibrator: insert vertically, withdraw slowly, spacing about 1.5 times the radius of action, avoid over-vibration.

Curing: keep concrete moist for at least 7 days for OPC, 10-14 days for blended cement or hot weather.

Plaster mix: 1:6 cement:sand for internal, 1:4 for external; thickness 12 mm for undercoat, 6 mm for finishing coat.

Plaster should be applied in coats, each scratched for key; do not exceed 15 mm total thickness in one coat.

Internal plaster is often 1:1:6 cement:lime:sand; lime improves workability and reduces shrinkage cracking.

Scale 1:100 means 1 mm on the drawing equals 100 mm on site; 1:50 doubles the detail size.

A site plan shows boundaries, building position, levels and services; a foundation plan shows footings and column positions.

Setting out: establish two base lines at right angles using 3-4-5, then offset with profiles and string lines.

A dumpy level with a staff measures reduced levels; the height of instrument equals backsight plus known reduced level.

Reduced level of a point equals height of instrument minus the foresight reading on that point.

A level survey closes with a check: sum of backsights minus sum of foresights equals last RL minus first RL.

A theodolite or total station sets out angles and distances; a total station records horizontal distance, vertical angle and coordinates.

Grid lines and centre lines are marked with nails or pegs and protected by offset pegs beyond the excavation.

Minimum depth of foundation is 0.9-1.0 m below natural ground level or below the zone of seasonal moisture change.

Safe bearing capacity of good soil is about 150-250 kN/m2; soft clay may be 50 kN/m2 or less.

Isolated footing carries a single column; a combined footing carries two columns; a raft spreads load over the whole area.

Pile foundations are used when soil bearing is poor or loads are heavy; end-bearing piles reach a hard stratum, friction piles rely on skin friction.

Concrete for footings is usually M15-M20 with 40-50 mm cover against earth; reinforcement cover in footings at least 50 mm.

Damp-proof course (DPC) is laid at plinth level, minimum 150 mm above ground, continuous and lapped 100 mm at joints.

Anti-termite treatment is applied to the soil, along the wall line and at junctions before and after laying the floor.

Under-reamed piles are used in expansive black cotton soil to resist uplift and swelling pressure.

Load-bearing wall thickness: half-brick (115 mm) for partition, one-brick (230 mm) for main walls, 1.5-brick (345 mm) for heavy loads.

Slenderness ratio of a wall is effective height or length divided by thickness; limit is about 27 for unreinforced masonry.

A column carries axial compression; a beam carries bending and shear; a lintel spans an opening and carries the wall above.

A pier is a thickened section of wall projecting on one or both faces, used to stiffen a long or high wall.

A buttress is an external pier built against a wall to resist lateral thrust, often with a battered face.

Reinforced concrete columns in masonry require a minimum of 4 bars of 12 mm diameter and ties at 150-200 mm spacing.

A plinth is the portion of wall between ground and floor level; a sill is the lower member of a window opening.

Expansion joints in long walls are provided at 20-30 m intervals to accommodate thermal movement.

Arch terms: span is the clear opening, rise is the height from springing line to crown, intrados is the inner curve, extrados the outer.

Semicircular arch rise equals half the span; segmental arch rise is less than half the span; flat arch has a slight rise.

A relieving arch transfers load around an opening; a lintel is a horizontal beam over an opening.

Lintel bearing is typically 100-150 mm on each side of the opening; a lintel carries the wall above it, not the roof load unless designed.

Stair terms: rise is the vertical height of one step, tread the horizontal going; 2R + T is about 600-640 mm for comfortable climbing.

Common stair proportions: rise 150-190 mm, tread 250-300 mm, width of stair 900-1200 mm, headroom at least 2100 mm.

Roof pitch for country tiles is 30-40 degrees; for plain tiles 40-45 degrees; corrugated sheet minimum pitch about 10 degrees.

Roof terms: ridge is the top line, eaves the lower edge, verge the gable edge, hip the sloping edge, valley the internal intersection.

Floor finishes: cement concrete 1:2:4 base with 1:2 cement mortar topping of 20-25 mm, or IPS 40 mm thick.

Tile adhesive coverage is checked by lifting a tile; minimum 80 percent coverage in dry areas and 95 percent in wet areas.

Ceramic tile joint width is 2-3 mm with grout; expansion joints every 6-8 m and at the perimeter.

Vitrified tiles have water absorption below 0.5 percent; ceramic tiles 3-10 percent; use the correct adhesive for each.

Skirting height is typically 100-150 mm; dado height in bathrooms 1200-1500 mm above floor.

Marble and granite are laid on a 20-30 mm cement mortar bed with slurry backing; joints are filled with matching grout.

A level floor is checked with a 3 m straight edge; allowable deviation is about 3 mm in 3 m.

Wood flooring requires a moisture content of 8-12 percent and a ventilated void or underlay beneath it.

Brickwork is measured in cubic metres; volume equals length times height times thickness, with deductions for openings over 0.1 m2.

Plaster is measured in square metres; deduct openings over 0.5 m2 and add for reveals and jambs.

Concrete is measured in cubic metres; formwork in square metres of contact area; reinforcement in kilograms or tonnes.

Standard brick count: 500 bricks per cubic metre of brickwork (with 10 mm joints, 190x90x90 mm brick).

Mortar for brickwork: about 0.30 m3 of wet mortar per cubic metre of brickwork; add 33 percent for dry volume.

Dry volume of mortar equals wet volume times 1.30-1.33 to allow for bulking and voids.

Rate analysis: cost per unit equals material cost plus labour cost plus plant plus overheads and profit (usually 10-15 percent).

Contingency in a preliminary estimate is 5-10 percent; a detailed estimate is prepared from drawings and a bill of quantities.

Efflorescence is a white salt deposit; brush off dry, do not wash, and identify the water source causing it.

Cracks wider than 0.3 mm in masonry are grouted with cement slurry or epoxy; hairline cracks are raked and filled.

Repointing: rake out the joint to 15-20 mm depth, clean, wet and fill with fresh mortar in layers.

Waterproofing of a roof: brickbat coba, cement-based coating or membrane; a minimum slope of 1:100 to 1:80 to drains.

A waterproofing membrane must be turned up at parapets and walls by at least 150 mm.

Dampness in walls is treated by a DPC, a damp-proof membrane, or by injecting a silicone or cementitious damp course.

Grouting of cracks uses a low-viscosity epoxy or cement grout injected under pressure through ports.

Spalling of concrete is repaired by removing loose concrete, treating reinforcement for rust, and patching with polymer-modified mortar.

A method statement describes the safe sequence of work; a risk assessment records hazards, likelihood and control measures.

A permit to work is required for hot work, confined spaces and work at height above 1.8 m.

A tool-box talk is a short briefing before work begins covering the task, hazards and controls.

Personal protective equipment: helmet, safety boots, gloves, eye protection, high-visibility vest, and hearing protection in noisy areas.

A bar chart shows activities against time; the critical path is the longest sequence of dependent activities.

Measurement sheets and daily progress reports record work done, labour, materials and plant used on site.

Under the Factories Act and Building and Other Construction Workers Act, the contractor must provide safety, welfare and first-aid facilities.

Communication on site uses standard terms: 'line', 'level', 'plumb', 'strike', 'tooth', and hand signals for crane operation.

Housekeeping: remove waste daily, keep walkways clear of 1.0 m minimum width, and stack materials at a stable height.

First aid: for a fracture, immobilise the limb and do not attempt to realign it; for burns, cool with water for 10-20 minutes.

Noise above 85 dB(A) over an 8-hour day requires hearing protection and a noise assessment.

Scaffold inspection is required before first use, at intervals not exceeding 7 days, and after alteration or bad weather.

Steel reinforcement grades: Fe415 and Fe500 denote yield strength in N/mm2; a 12 mm bar weighs 0.888 kg per metre.

Timber for shuttering should be seasoned to a moisture content of 12-15 percent to limit shrinkage and warping.

Glass is graded by thickness: 4-6 mm for ordinary glazing, 6-8 mm for larger panes; toughened glass is used in doors.

Bitumen grades 30/40, 60/70 and 80/100 denote penetration in tenths of a millimetre; 60/70 is common for waterproofing.

A concrete vibrator needle diameter 25-50 mm suits normal sections; a larger needle is used for mass concrete.

A plate compactor is used for compacting granular fill in layers of 150-200 mm.

A wall chaser or grinder with a diamond blade cuts chasing for conduits; depth should not exceed one-third of wall thickness.

A wheelbarrow holds about 0.05 m3 (50 litres); a head pan about 0.015 m3; use them for batching by volume.

A queen closer is half a brick cut lengthwise; a king closer is a brick cut so one end is half width.

A bevelled closer is used at corners in Flemish bond to keep the face pattern correct.

A bat is a piece of brick cut across its width; a three-quarter bat is used at quoins and openings.

In a one-and-a-half-brick wall, the two leaves are bonded with headers or wall ties; English bond gives the strongest bond.

Brick masonry in mud mortar is used in low-cost construction; cement mortar 1:6 is common for load-bearing walls.

A concrete block of 400x200x200 mm weighs about 18-20 kg; AAC block of the same size weighs about 8-10 kg.

Lintels over openings in brick walls bear 100-150 mm each side; a concrete lintel is often 100-150 mm deep.

A 'tooth' left for future work is one-quarter brick deep per course; a 'rack' is a straight vertical joint left for later bonding.

Mortar for plastering is often 1:4 to 1:6 cement:sand; for masonry 1:6 is common for load-bearing walls.

Adding 10-15 percent lime by volume of cement improves workability and reduces cracking.

Water-cement ratio for mortar is about 0.5-0.6 by mass; too much water causes shrinkage and weak bond.

Mortar should be mixed on a clean, impervious surface or in a mechanical mixer for at least 2 minutes after all materials are added.

Concrete cover: 40 mm for slabs, 40 mm for beams, 50 mm for columns, 50-75 mm for footings in contact with earth.

Formwork is struck when concrete has gained sufficient strength: sides of beams after 24 hours, soffits of slabs after 7-14 days.

Plaster should be cured for at least 7 days; rapid drying causes shrinkage cracks and dusting.

A scratch coat (key coat) is 6-9 mm thick and scored to provide a mechanical key for the finishing coat.

A benchmark is a fixed reference of known reduced level; a temporary benchmark is established on site for the work.

Contour lines join points of equal level; the closer the lines, the steeper the slope.

A section drawing shows a vertical cut through the building; an elevation shows the external face.

A bar bending schedule lists bar mark, diameter, shape, length and number of bars for reinforcement.

A trench fill foundation fills the excavation with concrete to a designed width and depth, saving formwork and labour.

A stepped footing spreads load from a wall in steps of 100-150 mm each side; the base width is designed from bearing capacity.

A grillage foundation uses steel beams in layers to spread heavy loads on weak soil.

Dewatering by pumping may be needed where the water table is above the foundation level; the excavation must be kept dry.

A lintel over an opening carries the wall above; the wall above an arch is carried by the arch, so the lintel is not loaded.

A column base distributes the column load to the footing; a slab on grade rests on the ground and is not a structural slab.

A retaining wall resists lateral earth pressure; the stem, base slab and shear key are its main parts.

A parapet wall is at least 1.0 m high on a roof for safety; it must have a coping to shed water.

A relieving arch has a rise of about one-eighth to one-quarter of its span and carries the wall above an opening.

A flat arch has a slight rise and is built of bricks on edge with a 10-15 mm camber.

A dog-legged stair has two flights with a half-space landing; a quarter-turn stair uses winders.

A trussed roof uses rafters, tie beam, principal rafter and struts; the pitch and span determine member sizes.

A screed is a thin layer of mortar over a structural floor to provide a level surface for the finish.

A floor drain must be set at least 10 mm below the surrounding tile surface to drain water.

Terrazzo is a mix of marble chips and cement, ground and polished; it is laid 20-25 mm thick.

Paint on plaster requires the plaster to be dry (moisture below 12-15 percent) and the surface sealed with a primer.

A bill of quantities lists items with description, unit and quantity; the contractor prices each item.

A preliminary estimate uses a plinth area rate; a detailed estimate is built up item by item from drawings.

Contingency and work-charged establishment are added to the estimated cost; centage charges cover overheads and profit.

A rate analysis for brickwork includes bricks, mortar, labour, scaffolding and curing, with a mason's output of about 1 m3 per day.

A damp-proof course must be continuous around the building and lapped 100 mm at joints and 150 mm at corners.

A waterproofing membrane on a roof is protected by a screed or tiles to prevent damage from traffic.

Cracks in plaster are raked out to a V shape, primed and filled with a polymer-modified mortar.

A leaking pipe or drain is located by a water test or dye test before repair; repair the cause, not just the stain.

A material requisition is raised before work starts; it lists the quantity, specification and required date.

A daily labour return records the number of workers by trade and the hours worked.

A quality check on brickwork includes plumb, level, line, joint thickness and bond pattern, recorded on a checklist.

A handover document lists completed work, defects and outstanding items, signed by the contractor and the client.