RBSE Sec Voc Construction cheat sheet

Standard brick size in India is 190 × 90 × 90 mm, with a nominal size of 200 × 100 × 100 mm including mortar joint; a modular brick weighs about 3 kg.

Ordinary Portland cement grades 33, 43 and 53 denote 28-day compressive strength in MPa; initial setting time must be at least 30 minutes, final setting not more than 600 minutes.

Bulking of sand: fine damp sand increases in volume up to about 20-30 percent; bulking is maximum at roughly 4-6 percent moisture content and disappears when sand is saturated.

Fineness modulus of coarse aggregate is found by sieve analysis; FM of fine aggregate 2.0-3.5 is acceptable for concrete, and higher FM means coarser sand requiring more water.

Workability of concrete is measured by slump (25-100 mm for normal RCC work), compaction factor test, or Vee-Bee consistometer; slump does not apply to very dry mixes.

Nominal concrete mix M15 is 1:2:4 and M20 is 1:1.5:3 by volume; M20 means characteristic cube strength of 20 N/mm² at 28 days with 5 percent failure probability.

Timber seasoning reduces moisture content to 10-12 percent for furniture and joinery; kiln seasoning is faster than air seasoning and reduces shrinkage and warping.

Mild steel has about 0.15-0.25 percent carbon and is ductile; HYSD bars Fe415 and Fe500 have 0.2 percent proof stress of 415 and 500 N/mm² respectively.

Depth of foundation by Rankine's formula: d = (q/γ) × [(1 - sin φ)/(1 + sin φ)]², where q is safe bearing capacity, γ unit weight of soil and φ angle of repose.

Minimum depth of foundation for a load-bearing wall is generally 900-1000 mm below ground level, and footing width increases with wall load and decreases with bearing capacity.

English bond alternates a header course and a stretcher course; Flemish bond alternates header and stretcher bricks in every course, giving better appearance.

Plastering thickness is normally 12-15 mm per coat; mortar ratio 1:4 or 1:6 for internal, 1:3 to 1:4 for external and for waterproofing work.

RCC slab thickness for a simply supported one-way slab is about span/30 for continuous and span/20 for simply supported conditions as a preliminary rule.

Damp proof course (DPC) of 40-50 mm cement concrete 1:2:4 with waterproofing compound is laid at plinth level across the full wall thickness.

Staircase: riser 150-190 mm and tread 250-300 mm; the relation 2R + T = 600-640 mm gives comfortable proportions, and headroom must be at least 2100 mm.

Doors: standard residential door height 2100 mm, width 900-1000 mm for main door; window sill height 750-900 mm and lintel level typically 2100 mm.

Scale of a drawing is the ratio of drawing length to actual length; a scale of 1:50 means 1 mm on paper represents 50 mm on site.

Plain scale shows two units (e.g., metres and decimetres); diagonal scale shows three units and can measure up to the second decimal of a unit.

Representative fraction (RF) = drawing length / actual length; RF 1:100 is a reducing scale, while RF 2:1 is an enlarging scale.

Plan is a top view cut at about 1.2 m above floor level; section shows internal details cut vertically; elevation shows the external face of the building.

Line conventions: continuous thick lines for visible outlines, dashed lines for hidden edges, chain lines for centre lines and section cutting planes.

Dimension lines are drawn thin and parallel to the measured edge, with arrowheads at ends; the dimension figure is placed above the line and read from the bottom or right.

A bar bending schedule lists bar mark, diameter, shape, cutting length and number; cutting length = length of all straight segments + hooks + bends − deductions for bends.

North line on a site plan is drawn with the arrow pointing north; contour lines at closer spacing indicate steep ground, wider spacing indicates gentle slope.

Long wall and short wall method: long wall length is centre-to-centre plus half width at each end; short wall length is centre-to-centre minus half width at each end.

Centre line method: total centre line length × width × depth gives quantity, but junctions must be deducted or added according to the number of meeting walls.

Earthwork in excavation is measured in cubic metres; brickwork in cubic metres; plastering and painting in square metres; and reinforcement in kilograms or quintals.

Standard brickwork deduction: no deduction for openings up to 0.1 m²; for larger openings deduct the full area, and deduct RCC lintels and beams separately.

Rate analysis of a work item = cost of materials + labour + plant + overheads (about 5-10 percent) + contractor profit (usually 10 percent) + GST as applicable.

Contingency allowance in a detailed estimate is typically 3-5 percent of the estimated cost; work-charged and departmental charges are added separately.

Approximate estimate by plinth area rate = plinth area × plinth area rate; cube rate method uses volume of the building and is used for multi-storeyed buildings.

Valuation: depreciation by straight line method = (original cost − scrap value)/life; by constant percentage method, value after n years = C × (1 − r)^n.

Chain survey: 1 chain = 20.1168 m (66 ft); 1 link = 0.2012 m; 100 links make one chain, and 1 acre = 10 square chains = 4046.86 m².

Ranging is fixing intermediate points on a straight line between two stations; direct ranging is done when stations are intervisible, indirect ranging when they are not.

Obstacles to chaining: for a pond, use perpendicular or similar-triangle method; for a river, use the similar-triangle or sine rule method.

Prismatic compass: magnetic bearing measured from magnetic north; true bearing = magnetic bearing ± magnetic declination, and local attraction is detected by fore and back bearings differing by 180°.

Levelling: height of instrument (HI) = reduced level of station + backsight; reduced level of next point = HI − foresight. Rise and fall method checks ΣBS − ΣFS = ΣRise − ΣFall = last RL − first RL.

Contouring: direct method is accurate but slow; indirect methods include grid, radial and cross-section methods; contour lines never cross each other except at an overhanging cliff.

Setting out a right angle: 3-4-5 method using a tape, or theodolite method by turning 90° from a reference line; the diagonal check between corners confirms the rectangle.

Plane table surveying: orientation by back sighting or magnetic needle; the three-point problem is solved by the Lehmann trial and error method or the Bessel method.

Masonry tools: trowel (gauging and lifting mortar), plumb bob (verticality), spirit level (horizontality), mason's square (right angles), and line and pins for course alignment.

Carpentry tools: ripsaw cuts along the grain, crosscut saw cuts across the grain, tenon saw for fine joints; try square for 90° checking and marking gauge for parallel lines.

Wood joints: lap joint, mortise and tenon (strongest for framing), dovetail (resists pulling apart), and dowel joint; glue increases joint strength but does not replace correct fit.

Excavators are rated by bucket capacity in cubic metres; a backhoe digs below its track level, while a shovel digs above; dragline is used for long reach and soft material.

Concrete mixers: tilting drum mixer for dry mixes and large aggregate; non-tilting drum for wet mixes; nominal drum capacity is about 1.5 times the batch volume.

Vibrators: needle vibrator for beams and columns (insert every 300-500 mm and withdraw slowly), surface vibrator for slabs, and form vibrator for precast units.

Scaffolding: putlog scaffold uses putlogs placed in wall holes; independent scaffold stands clear of the wall; standards are vertical members and ledgers are horizontal members.

Safety in workshop: chisels and screwdrivers must be sharp and never used as pry bars; power tools must be checked for earthing before use and guarded where required.

Personal protective equipment: helmet, safety shoes, high-visibility vest, gloves, goggles and full-body harness are mandatory on site; harness anchorage must be above shoulder level.

Scaffold safety: working platform must be at least 600 mm wide, fully boarded, with guard rails at 950-1000 mm and toe boards at least 150 mm high.

Excavation safety: shoring or sloping is required for trenches deeper than 1.2-1.5 m; ladders must be provided for access and spoil heaps kept at least 1 m from the edge.

Electrical safety on site: use 110 V or 24 V for portable hand lamps in wet areas; earth leakage circuit breakers and proper earthing are mandatory.

First aid: for burns, cool with clean running water for at least 10 minutes and cover with sterile dressing; do not apply oil or grease to a burn.

Fire safety: Class A fire (wood, paper) uses water; Class B (oil, petrol) uses foam or dry powder; Class C (gas) uses dry powder or CO2; never use water on electrical fires.

Environmental control: dust suppression by water sprinkling, covering of loose material during transport, and segregation of construction waste into recyclable, inert and hazardous bins.

Occupational health: prolonged exposure to silica dust causes silicosis; noise above 85 dB(A) for 8 hours requires hearing protection, and cement contact causes dermatitis.

A contractor's licence and GST registration are prerequisites for bidding on public works; PWD, CPWD and municipal bodies each have their own registration categories by value of work.

Costing versus pricing: cost includes material, labour, plant, overheads and finance charges; price adds margin and is governed by market competition and tender conditions.

Tender documents usually include notice inviting tender, bill of quantities, specifications, drawings, conditions of contract and the form of tender with earnest money deposit.

Earnest money deposit (EMD) is typically 2-5 percent of the estimated cost; security deposit is usually 5-10 percent retained from running bills.

Cash flow management: retainage, delayed payments and material credit cycles determine working capital; a project can be profitable yet fail due to poor cash flow.

Labour law essentials: wages must be paid within the prescribed period, working hours and overtime are regulated, and registers of attendance and wage payment must be maintained.

Employability skills: a trade certificate plus knowledge of IS codes, quantity take-off, autoCAD and safety compliance improves employability in construction supervision roles.

Business planning: a simple break-even point = fixed cost / (selling price per unit − variable cost per unit); it tells the minimum volume of work needed to avoid loss.

A practical project report should contain title, objectives, tools and materials used, procedure, observations or measurements, calculations, results, and conclusion.

Viva questions commonly test definitions: what is the fineness modulus of sand, why is curing needed, what is the difference between a header and a stretcher, and what is DPC.

Curing must continue for at least 7 days for ordinary Portland cement concrete and 10-14 days for blended cements; curing improves strength and reduces shrinkage cracks.

When measuring a brick wall on site, take three readings at different points and use the average; record thickness, length and height to the nearest 5 mm.

Common viva check: compute the quantity of a 3 m × 2.4 m brick wall of 230 mm thickness; the answer is 1.656 m³, ignoring openings.

Workmanship checks: plumb of a column within 5 mm per storey, level of slab within 10 mm, and gap between tiles not more than 2 mm for a neat finish.

Testing on site: slump test for workability, cube test at 7 and 28 days for strength, and the rebound hammer for a rough indication of surface hardness.

Documentation: maintain a site diary with date, weather, labour strength, work done, materials received and any instructions received from the engineer.

Project work should be original: record your own measurements, sketches and calculations; copying another student's report is treated as malpractice.

For a masonry project, prepare a small wall of 1 m × 1 m using English bond and check verticality with a plumb bob and level with a spirit level.

For a concrete cube project, cast three 150 mm cubes, cure them and test at 7 and 28 days; report the average of three results as the representative strength.

For a surveying project, set out a rectangular plot using the 3-4-5 method, close the traverse and report the closing error; a closing error within 1 in 1000 of the perimeter is acceptable.

For an estimation project, take off quantities from your own measured drawing and prepare a rate analysis for at least one item such as brickwork in cement mortar 1:6.

Viva preparation: be ready to explain why you chose a particular method, what errors you observed, and how you would control them on a real site.

Safety in the project: wear PPE during all practical work, obtain instructor permission before using power tools, and clean the workplace after finishing.

Report presentation: include a neat title page, index, aim, materials, procedure, observations table, calculations, result, conclusion and a reference list of IS codes.

A quotation should state scope, unit rates, taxes, payment terms and validity period; an unclear scope statement is the most common cause of disputes.

Record keeping: maintain measurement books, bills, vouchers, labour registers and material receipts; these are required for GST filing and for settling claims.

Subcontracting risk: verify the subcontractor's licence, insurance and past work; retain a portion of payment until defect liability period ends.

Defect liability period for civil works is commonly 12 months from completion; the contractor must rectify defects at own cost during this period.

Digital tools for a small contractor: spreadsheet-based BOQ, accounting software for GST invoices, and messaging apps for daily site coordination.

Customer relationship: a written work order, agreed drawings and a signed completion certificate reduce disputes and build repeat business.

A viva examiner typically asks the candidate to explain the difference between nominal mix and design mix, and to state the IS code for concrete (IS 456).

For a plumbing or electrical trade project, include a single-line diagram or layout drawing, a material list, and a test result such as a pressure or insulation test.

When presenting a project, state the aim in one sentence, then show the procedure in numbered steps, and finally state the result with its unit and tolerance.

Common mistake to avoid: mixing units in calculations, such as entering millimetres into a formula that requires metres; convert before computing.

Record actual site observations rather than textbook values; if a slump result differs from the expected range, state the likely cause such as excess water.

Assessment of practical work usually covers correct procedure, accuracy of measurement, safety compliance, neatness of record and clarity in viva.

Keep a rough field book for original readings and a fair record book for the final neat report; never overwrite a reading, strike it out and initial the correction.

For a workshop project, submit the job with dimensions checked against the drawing and a tolerance statement, for example ±1 mm on a 100 mm dimension.

Group project work must state each member's contribution; the viva may ask any member about any part of the work.

Time management: divide the project into planning, execution, testing and reporting phases, and keep a dated log of progress for the viva.

A safety induction is required before a worker enters the site; visitors must sign in, wear PPE and be escorted.

Incident reporting: record the time, place, persons involved, cause and action taken; near-miss reporting prevents future accidents.

Housekeeping: keep walkways clear, stack material at a stable height and never leave open floor openings unguarded; cover or barricade them.

Welfare facilities: drinking water, toilets, washing facilities and a first-aid box with trained personnel must be available at every site.

Emergency plan: display emergency numbers, mark assembly points and keep a stretcher and fire extinguishers accessible and inspected.

Steel tools: hacksaw blade teeth per inch (18 or 24 TPI) are chosen by material thickness; a file cuts on the forward stroke, and a cold chisel is held at about 60° to the work.

Measuring tools: steel rule, vernier caliper (least count 0.02 mm), micrometer (least count 0.01 mm) and try square; check zero error before use.

Drilling: drill speed decreases as drill diameter increases; use cutting fluid when drilling steel to cool the bit and clear chips.

Brick cutting: use a bolster chisel and club hammer for a clean face; cut on the face side and dress the edges with a brick hammer.

Concrete equipment selection: batching plant for large volume, transit mixer for transport, concrete pump for high-rise placement, and power float for slab finishing.

Total station measures horizontal and vertical angles and slope distance, and computes coordinates; it replaces chain, compass and level for most site setting out.

GPS/GNSS gives coordinates in a global datum; for site work, local coordinates must be transformed and checked against at least two known control points.

Errors in levelling: parallax, bubble not centred, staff not vertical, and refraction; the two-peg test checks the collimation error of a level.

Traverse survey: sum of interior angles of a closed polygon = (2n − 4) × 90°; the angular misclosure must be distributed before computing coordinates.

Deduction rules for plastering: deduct openings exceeding 0.5 m²; no deduction for openings up to 0.5 m², and no addition for jambs, soffits and sills up to 300 mm width.

For steel reinforcement, cutting length of a bar with a 90° bend = straight length + 2 × (bend allowance) − deduction; bend deduction depends on bar diameter and bend angle.

Abstract of cost is prepared from the detailed estimate by multiplying quantity by rate; it gives the total cost and is used for administrative approval.

Bar bending schedule weight = (d²/162) × length in metres, where d is bar diameter in mm, giving weight in kg per metre.

A section drawing shows hatched cut surfaces; the hatching pattern identifies the material, such as diagonal lines for brick and dots for concrete.

Symbols: a circle with a cross for a ceiling fan, a rectangle with a diagonal for a wash basin, and a triangle for a water closet outlet direction.

Levels are written as RL (reduced level) with a datum, for example +0.450 m; the floor level is usually taken as ±0.000 m.

Drawing sheet sizes: A0 is 841 × 1189 mm; each smaller size halves the larger dimension, and title blocks are placed at the bottom right.

Concrete grades for elements: M20 for RCC slabs and beams, M25 for columns and water-retaining structures; minimum cement content and maximum w/c ratio are specified by exposure condition.

Formwork removal times: sides of beams and columns after 24-48 hours, soffit of slab after 7-14 days, and props under beams left longer depending on span.

Brick masonry mortar joint thickness is 10 mm; bricks must be soaked in water before laying to prevent absorption of mortar water.

Roof slopes: RCC flat roof 1:50 to 1:100 for drainage; corrugated sheet roof minimum 1:6 to 1:4 depending on sheet profile and rainfall.

Lime: fat lime slakes readily and is used for whitewashing; hydraulic lime sets under water and is used in masonry mortar; slaking is adding water to quicklime.

Aggregate grading: well-graded aggregate has fewer voids, reducing cement paste requirement; gap-graded mixes are avoided in normal concrete.

Water absorption of good quality bricks should not exceed 20 percent by weight, and compressive strength of a first-class brick is at least 10 N/mm².

Bitumen is graded by penetration or viscosity; it is used for road surfacing and waterproofing, and its viscosity decreases as temperature rises.

Units of measurement: steel doors and windows in square metres or numbers, pipes in running metres, and earthwork in cubic metres.

Percentage rate method of approximate estimate uses a percentage of the cost of a similar completed project, adjusted for time and location.

A bill of quantities is a priced or unpriced list of items with quantities; it differs from a schedule of rates, which gives unit rates for items.

Contingency and escalation must be separated: contingency covers unforeseen items, while escalation covers price rise over the project duration.