NSSCO Building Studies 6186 cheat sheet

Personal protective equipment (PPE) hierarchy on site: helmet, safety boots, high-visibility vest, eye protection, hearing protection, gloves, dust mask; PPE is the last line of defence after elimination and engineering controls.

Scaffold rules: working platform fully boarded, minimum 600 mm wide, toe boards at least 150 mm high, guardrails at 1 m and 0.5 m, tied to the structure, inspected before first use and at least every 7 days.

Excavation safety: support or batter sides of trenches deeper than 1.2 m; keep spoil and materials at least 1 m from the edge; provide a ladder within 7.5 m of any worker; test for gas before entry.

Ladder angle rule: 1 in 4 (about 75 degrees) - 1 unit out for every 4 units up; ladders extend at least 1 m above the landing point when used for access to a roof.

Manual handling limit guide: two-person lift for loads above about 25 kg; keep load close to the body, back straight, lift with legs, no twisting while loaded.

Site fire precautions: extinguishers selected by class (water for Class A, foam for flammable liquids, CO2 for electrical), hot-work permit, fire assembly point, escape routes kept clear.

Electrical safety on site: 230 V reduced to 110 V centre-tapped earth for portable tools; RCD protection; inspect leads for damage; no trailing cables across walkways.

Accident reporting: record all injuries in the accident book; report fatalities, major injuries and dangerous occurrences to the labour/health authority without delay.

Housekeeping rules: clear walkways, stack materials safely at a stable height, remove waste daily, and barricade openings and voids immediately.

Scale is drawing size : real size. 1:100 means 1 mm on paper = 100 mm on site; 1:50 shows twice the detail of 1:100; site plans are commonly 1:500 or 1:1250.

Standard line types: continuous thick for outlines, continuous thin for dimensions and hatching, dashed for hidden detail, chain dotted for centrelines and grid lines.

Orthographic projection: first-angle places the plan below the elevation; third-angle places the plan above the elevation. State the convention used.

A floor plan is a horizontal section cut about 1.2 m above floor level, looking down; it shows walls, openings, fittings and room labels.

Elevations show external faces with finished ground level (FGL), roof pitch, window and door positions, and levels in metres above a datum.

Section drawings show construction build-up (foundation, floor, wall, roof) with hatching codes for concrete, brickwork, timber and insulation.

Dimensioning rules: dimension lines outside the drawing, projection lines from the feature, all dimensions in millimetres unless stated, no repeated dimensions.

A title block records project name, drawing number, scale, date, revision letter and author; a revision cloud marks changed areas.

A schedule of works or door/window schedule lists each item with a type code, size and material so quantities can be taken off the drawing.

A specification states quality and workmanship (materials, standards, testing); the drawing states quantity and geometry - both are needed for a complete contract.

Types of specification: performance specification (states required outcome), prescriptive specification (states exact product and method), and proprietary specification (names a manufacturer's product).

A bill of quantities (BQ) is measured from drawings and specifications; it lists items with description, unit and quantity, and forms the basis for tendering.

Units of measurement: cubic metres for excavation and concrete, square metres for plastering and roofing, linear metres for skirting and gutters, number (nr) for doors and fittings.

Preliminaries cover site establishment, insurance, supervision, temporary works and water/electricity - items not fixed to the building itself.

A contract must identify the parties, scope, price, time for completion, payment terms, retention and dispute procedure.

Retention is a percentage (commonly 5–10%) held from each payment as security for defects; released in part at practical completion and the balance after the defects liability period.

A variation is a written instruction changing the scope; it must be valued before or after execution and recorded so the contract sum can be adjusted.

Approved drawings are stamped and dated; only the latest revision is used on site, and superseded copies are withdrawn to avoid building to outdated information.

The 3-4-5 method sets a right angle: measure 3 units along one line, 4 units along the other, and adjust until the diagonal reads 5 units (Pythagoras: 3² + 4² = 5²).

Profile boards are set beyond the excavation line and carry nails marking wall centre lines, faces and foundation width; strings stretched between profiles guide excavation.

The building line is fixed from the site boundary or a permanent reference; a datum peg or benchmark transfers level to the works.

Levelling with a dumpy or automatic level: set up midway, take a backsight on the benchmark, height of collimation = benchmark level + backsight; reduced level = collimation − foresight.

Rise and fall method checks: sum of backsights − sum of foresights = last reduced level − first reduced level.

Site clearance sequence: remove vegetation and topsoil, strip and stockpile topsoil separately, demolish obstructions, then reduce level to formation.

Setting out a simple rectangular building: establish one corner and two lines, use the 3-4-5 method at each corner, and check both diagonals are equal.

Grid lines for larger buildings are set from a baseline and referenced to permanent marks outside the excavation so they survive groundworks.

Function of a foundation: transfer building loads to the ground without exceeding the soil's safe bearing capacity and without excessive settlement.

Strip foundation rule of thumb: width at least three times the wall thickness, thickness at least equal to the projection beyond the wall; depth below ground at least 1 m or below frost line.

Trench fill is economic where concrete is cheap and labour dear; it uses more concrete but less excavation and formwork than a strip footing.

Pad foundations carry isolated columns; raft foundations spread load over the whole footprint where soil is weak or settlement must be minimised.

Pile foundations pass load through weak upper soil to a firm stratum by end bearing or friction; used on soft clay, made ground or where water is present.

Concrete grades: a common foundation mix is 1:3:6 (cement:sand:aggregate) or strength class C15/C20; a lean concrete blinding layer about 50 mm is placed under footings.

Damp-proof course (DPC) is laid at least 150 mm above external ground level to stop rising damp; damp-proof membrane (DPM) under a ground floor slab.

Concrete curing: keep damp for at least 7 days (longer in cold weather); do not strip formwork from sides of foundations before the concrete has gained strength.

Standard brick dimensions (Southern Africa) are 222 × 106 × 73 mm; with a 10 mm joint a module of 235 × 120 × 85 mm is used for setting out.

Bonding rules: a half-brick wall uses stretchers only; a one-brick wall uses English bond (alternate stretcher and header courses) or Flemish bond (header and stretcher alternating in each course).

Mortar mix by volume: 1:3 for high-strength/exposed work, 1:4 to 1:6 for general walling; lime or plasticiser improves workability.

Cavity walls: two leaves separated by a 50–75 mm cavity, tied with wall ties at about 900 mm horizontally and 450 mm vertically; the cavity is kept clear of mortar droppings.

Concrete mix designations: nominal mixes 1:3:6 (C15), 1:2½:3½ (C20), 1:2:4 (C25), 1:1½:3 (C30); water-cement ratio controls strength and durability.

Reinforcement: main bars carry tensile force, links/stirrups resist shear and hold bars in position; cover to reinforcement protects against corrosion and fire (typically 25–40 mm).

Compaction of concrete by poker vibrator removes air voids; over-vibration causes segregation, under-vibration causes honeycombing.

Blockwork uses concrete blocks (commonly 390 × 190 × 190 mm) laid in stretcher bond; hollow blocks may be grouted and reinforced for strength.

Ground floor types: solid concrete slab on hardcore with DPM, or suspended timber floor with sleeper walls, wall plates, joists and floor boards.

Hardcore bed is 100–150 mm of compacted broken stone blinded with sand; the DPM laps over the damp-proof course in the wall to form a continuous barrier.

Concrete ground slab thickness typically 100–150 mm, often with a mesh fabric reinforcement (e.g. A142) to control cracking.

Suspended timber floor joists: size chosen from span tables, spaced at 400 or 600 mm centres, with ventilation openings in the sleeper walls and air bricks in the external wall.

Upper floors: timber joists with herringbone strutting between them, or a reinforced concrete slab; trimming joists and trimmers form openings for stairs and chimneys.

Floor finishes: screed (sand-cement 1:3 to 1:4) laid 40–75 mm thick over concrete; tiles, timber or vinyl laid over the screed after curing.

Sound and thermal insulation: resilient quilt between joists or rigid insulation under screed reduces impact and airborne noise.

Slope to falls: bathroom and shower floors fall about 1:60 to 1:80 to a floor gully; external paving falls 1:60 to 1:80 away from the building.

Roof pitch = rise ÷ run (tangent of the angle); a roof rising 1 m over a 2 m run has a pitch of 1:2, about 26.5 degrees.

Common timber sizes: rafters 38 × 150 mm or 50 × 150 mm; ceiling joists 38 × 100 mm; purlins and binders sized from span tables.

Roof members: ridge board at the apex, rafters from wall plate to ridge, purlins supporting rafters, ceiling joists tying the feet, collar or binder restraining the rafters.

Wall plate is bedded level on the wall and strapped down; it distributes rafter loads and is anchored against wind uplift.

Pitch limits: corrugated iron sheets work down to about 5–10 degrees with end laps; concrete or clay tiles need steeper pitches (about 17.5–22.5 degrees minimum depending on type).

Roof covering laps: side lap one corrugation, end lap at least 150 mm for sheeting; tiles are double-lapped and fixed with nails or clips.

Carpentry joints: halving joint for crossing timbers, mortise and tenon for framing, dovetail for drawer corners, housing joint for shelving, scarf joint for lengthening.

Underlay (building paper or membrane) is laid under the covering to shed any wind-driven rain that passes the sheets; eave ventilation keeps the roof space dry.

Cold water supply: mains → water meter → stop valve → storage tank or direct to fittings; a float valve controls tank filling and an overflow pipe discharges safely.

Hot water: geyser/cylinder with thermostat set about 55–60 °C to control Legionella; a temperature-and-pressure relief valve and expansion control are required.

Pipe materials: copper, PEX and PVC/UPVC for water; UPVC or PVC for soil and waste; falls for drainage pipes are typically 1:40 to 1:60 (about 18–25 mm per metre for 100 mm pipe).

Soil stack carries WC discharge and terminates above roof level for ventilation; a trap (P-trap or bottle trap) holds a water seal of about 50 mm to stop sewer gas entering.

Drainage: inspection chamber at changes of direction, at junctions and at intervals (commonly every 45 m for straight runs); rodding eyes allow clearing blockages.

Electrical circuit basics: Ohm's law V = I × R; power P = V × I; cable size is chosen for current-carrying capacity, volt drop and disconnection time.

Earthing and bonding connect exposed metalwork to earth; an RCD (residual current device) trips at 30 mA for socket circuits in wet areas.

Lighting circuits are wired in loop-in or radial configuration; socket circuits are ring or radial; all connections are made in enclosures, never buried in plaster without protection.

Concrete constituents: cement, fine aggregate (sand), coarse aggregate (stone), water, and admixtures; aggregate should be clean, hard and graded.

Cement types: ordinary Portland (OPC) for general use, rapid-hardening for early strength, sulphate-resisting for aggressive ground or marine conditions.

Water-cement ratio rule: lower ratio gives higher strength and durability; excess water increases workability but reduces strength by about 5% per 0.01 increase in ratio.

Timber: softwoods (pine) for general carpentry, hardwoods for joinery and exposed work; timber is seasoned to reduce shrinkage and movement.

Timber defects: knots, shakes, splits and sapwood reduce strength; wood-boring insects need treated timber in contact with ground or masonry.

Steel reinforcement: high-yield bars (e.g. 8, 10, 12, 16, 20, 25 mm) with ribbed surface for bond; mild steel is used for links.

Masonry units: clay bricks (durable, good in wet conditions), calcium silicate bricks, concrete blocks (cheap, good thermal mass, need careful damp protection).

Paint systems: primer, undercoat and finish coat; exterior wood needs preservative treatment and a flexible paint to accommodate movement.

Setting-out and measuring: steel tape, chalk line, spirit level, plumb bob, dumpy/automatic level and staff, laser level, builder's square.

Masonry tools: bricklayer's trowel, bolster and club hammer for cutting, cold chisel, pointing trowel, jointing/ironing tool, brick line and corner blocks.

Carpentry hand tools: claw hammer, saws (rip, crosscut, tenon), chisels, plane, try square, marking gauge, brace and bits.

Power tools: circular saw, jigsaw, hammer drill, angle grinder, concrete mixer, poker vibrator, plate compactor; each requires guarding, correct blade/bit, and PPE.

Concrete equipment: mixer (drum or pan), wheelbarrow, vibrator, screed board, float and trowel; mix by volume on site, measure accurately.

Earthmoving: spade, pick, crowbar, wheelbarrow, plate compactor for hardcore; excavator for bulk work with banksman control.

Tool maintenance: keep cutting edges sharp, oil metal parts, store tools dry, inspect electrical leads and plugs before use, and never use a damaged tool.

Safety with power tools: use the correct voltage (110 V on site), check guards, do not remove the earth pin, and switch off before changing blades or bits.

Plaster mix: 1:3 to 1:4 sand-cement for backing coats, with a finishing coat of finer mix or gypsum plaster; thickness about 10–15 mm in two coats.

Rendering: external sand-cement render 1:4 with a water-repellent additive; provide bell-mouth drip at the base and movement joints in large areas.

Screeds: sand-cement screed 1:3 to 1:4, 40–75 mm thick; cure and allow to dry before laying tiles or vinyl, and check moisture before covering.

Tiling: bed tiles on adhesive or mortar with even joints; floor falls to gully in wet areas; grout after adhesive has set; use spacers for consistent joints.

Painting sequence: prepare surface (clean, fill, sand), prime, undercoat, then two finish coats; allow drying time between coats and protect from dust.

Wood finishing: sand with progressively finer paper, apply wood filler, stain, then varnish or seal; exterior wood needs a preservative base.

Suspended ceilings: grid of main runners and cross tees at 600 mm centres, tiles laid in, level checked with a laser or string line.

Defects in plaster: crazing from too-rich mix, shrinkage cracks from rapid drying, and blowouts from unsound background - cure causes, not just symptoms.

Maintenance types: planned preventive (scheduled inspections and servicing), reactive (repair after failure), and condition-based (act on inspection findings).

Damp diagnosis: rising damp (no DPC or bridged DPC, tide mark at about 1 m), penetrating damp (defective render, joints or roof), condensation (cold surfaces, poor ventilation).

Crack classification: hairline cracks (settlement or shrinkage) are usually cosmetic; cracks wider than about 5 mm or stepped diagonal cracks in masonry indicate structural movement and need investigation.

Roof maintenance: clear gutters and downpipes of leaves, replace slipped or broken tiles, check flashings at chimney and wall junctions, re-fix loose sheeting.

Concrete repair: remove loose and carbonated concrete, clean reinforcement, apply rust inhibitor, then patch with repair mortar or polymer-modified concrete.

Timber repair: cut out rot to sound wood, treat with preservative, splice or scarf new timber, and eliminate the water source.

Repointing: rake out defective mortar to about twice the joint width, wet the joint, and press in new mortar of similar strength to the original.

Plumbing repair: isolate the supply at the stop valve first, drain the pipe, replace washers or fittings, then test under pressure before boxing in.

A business plan for a building contractor covers the market, services offered, pricing method, cash-flow forecast, equipment list, staffing and legal registration.

Cost categories: fixed costs (rent, insurance, licences) do not change with output; variable costs (materials, labour, fuel) change with each job.

Break-even point in units = fixed costs ÷ (selling price per unit − variable cost per unit).

Mark-up is added to cost to give price: price = cost × (1 + mark-up %); margin is profit as a percentage of price, not cost.

Cash flow is the timing of money in and out; a profitable job can still fail a business if payments arrive after wages and material bills are due.

Tendering: read the documents, take off quantities, price labour, material, plant and overheads, add risk and profit, then submit on time in the required format.

Record keeping: keep invoices, delivery notes, wage sheets and a job file for each contract; these support claims, tax returns and dispute resolution.

Client relations: confirm instructions in writing, agree variations before doing the work, and keep a site diary recording weather, labour and delays.

Labour constant is hours per unit of work; labour cost = quantity × labour constant × hourly rate.

Material cost = quantity × unit rate, plus a wastage allowance (commonly 5–10% for bricks and tiles, less for sheet materials).

Unit rates for masonry: bricks per square metre of half-brick wall = 1 ÷ (module length × module height) ≈ 60 bricks/m² for a 222 × 106 × 73 mm brick with 10 mm joints.

Mortar volume for brickwork is roughly 0.02–0.03 m³ per m² of half-brick wall; order sand and cement from the measured wall area.

Programme tools: bar chart (Gantt) shows activities against time; critical path method (CPM) identifies the longest sequence of dependent activities that sets the project duration.

Float (slack) is the time an activity can be delayed without delaying the project; critical activities have zero float.

Valuation and payment: measure work executed at intervals, apply contract rates, deduct retention, and issue an interim certificate for payment.

Cost control: compare actual cost against budget for each work package; investigate variances in labour hours, material wastage and plant standing time.

Delay and disruption: record the event, notify the client within the contract period, and quantify the effect on time and cost separately.