Certificate III in Carpentry cheat sheet

Hierarchy of control, highest to lowest: eliminate the risk, substitute, engineer (isolation/guards), administrate (SWMS, signage, training), then PPE as the last line of defence.

SWMS (safe work method statement) is mandatory for high-risk construction work, must list the work, the hazards, the controls and be reviewed when the task changes; workers must be consulted.

Working at height: fall arrest or restraint is required where a person could fall 2 m or more, or could fall any distance onto a hazardous surface; edge protection, covers and perimeter guardrails take priority over harnesses.

Ladder rule (4:1): set the ladder base out one unit for every four units of height; extend at least 1 m above the landing; maintain three points of contact and do not work from the top two rungs.

Roof pitch: rise over run, expressed in degrees or as rise:run (e.g. 1:4 = 14°). Rafter length = run ÷ cos(pitch), or use the set-out method with a steel square.

Pythagoras for squaring: 3-4-5 triangle (or 6-8-10, 1.5-2-2.5 m) to check a right angle; diagonal of a rectangle must be equal both ways before laying out plates.

Nominal vs actual timber: nominal sizes are the rough green size; actual dressed sizes are smaller (e.g. 100x50 nominal ≈ 90x45 actual). Design spans and loads use actual dressed dimensions.

Scale reading: scale = drawing length ÷ real length. For 1:100, 1 mm on the plan = 100 mm real; for 1:50, 1 mm = 50 mm real.

Timber seasoning: seasoned timber is dried to a moisture content near service conditions (typically 10-15% for framing), reducing shrinkage, checking and movement after installation.

Formwork design loads include concrete weight (≈24 kN/m³ for normal-weight concrete), plus live load for workers/equipment, plus impact and lateral pressure from placing; formwork must be designed, braced and propped, not just built.

Stripping times are governed by concrete strength gain, not a fixed clock: sides of beams and columns can be removed once the concrete holds its shape; soffits and props stay until the specified strength is reached (commonly verified at 7 and 28 days).

Stair rule of thumb: 2R + G = 550-700 mm (target ≈600-630 mm) for comfortable rise-to-going; typical rise 150-190 mm and going 240-300 mm. Total rise ÷ number of risers gives each rise; all risers in a flight must be equal.

Roof geometry: true length of a common rafter = half-span ÷ cos(pitch). Hip/valley rafters = common rafter length ÷ cos(plan angle) (for a square hip, ÷ cos45° ≈ ×1.414).

Cladding and flashing: cavity and weep holes allow drainage and ventilation behind the cladding; flashings must lap in the direction of water flow (upper laps over lower), and head flashings shed water clear of the wall.

Eaves and fascia set-out: fascia height is set from the top plate plus the birdsmouth seat cut; overhang is measured horizontally from the wall line, so the rafter tail must be checked against the specified overhang.

Fit-out: door and window openings are set out from a datum and checked for plumb, level and square (diagonals equal); reveal and jamb clearances allow for packing, and hardware requires framing or blocking in place before linings close.

Decks and subfloors: bearers sit under joists, joists run across bearers, and decking boards run across joists; spacing is set by the span table for the timber grade, load and member size - never by habit.

Material take-off: area = length × width; volume = area × thickness. Add a waste allowance (commonly 5-10% for sheet goods and framing, more for cut-heavy work) then round up to purchasable pack or sheet sizes.

Concrete volume: V = length × width × depth, all in metres; divide by 1 m³ to get cubic metres. Add 5-10% for slab compaction and spillage; order in full cubic metres.

Labour and cost estimate: total cost = materials + labour (hours × rate) + plant/equipment + subcontractors + overheads + margin. Contingency is a separate line, not hidden inside item rates.

WHS duties: the PCBU must manage risk so far as reasonably practicable; workers must take reasonable care of themselves and others, follow controls, and report hazards and incidents. Notifiable incidents (death, serious injury/illness, dangerous incident) must be reported to the regulator immediately.

Hazardous substances and silica: obtain and follow the SDS, keep a register, use controls in order (water suppression, on-tool extraction, ventilation) and fit-tested respiratory protection for crystalline silica dust.

Environmental controls: sediment fencing downslope of works, stabilised entry/exit, covered loads, bunded storage of fuels and chemicals, and no washout into stormwater - all stormwater drains lead to waterways.

Communication and documentation: variations, delays and EOT claims must be in writing and confirmed before work proceeds; keep a daily site diary of weather, labour, deliveries and instructions.

Quality and compliance: work to the NCC (Building Code) and Australian Standards referenced by the contract; hold points and inspections (slab, frame, waterproofing, final) must be booked and passed before covering up.

Business basics for contractors: ABN required for invoicing, GST registered above the threshold, and home building work must be covered by the correct licence class and domestic building insurance where the project value exceeds the threshold.