CPC31020 Solid Plastering cheat sheet

Hierarchy of control, highest to lowest: eliminate the hazard, substitute, isolate, engineer controls, administrative controls, then PPE as the last line of defence.

Silica dust from cutting, sanding or mixing plaster is a respirable hazard: dry sweeping is prohibited; use wet methods, on-tool extraction or Class M/H vacuum, and RPE fit-tested to AS/NZS 1715.

Asbestos-containing materials may be present in pre-1990 buildings; friable material must not be disturbed, and work stops until identification and a licensed removalist are arranged.

Scaffold and trestle platforms require guardrails, mid-rails and toe boards; working platforms are at least 450 mm wide and planks are secured against movement.

Ladder use is a short-duration, light-task control: 1-in-4 set-up angle, three points of contact, and no work from the top two rungs.

Hazardous substance labels and SDS follow the GHS: the label carries signal word, pictograms, hazard statements and first-aid directions; the SDS has 16 sections.

Manual handling risk rises with bag weights, hawk-and-trowel reach and overhead ceiling work; mechanical aids, team lifting and rotating tasks reduce cumulative spinal load.

Waste segregation: set plaster and render residue is kept out of stormwater drains; washout is contained and settled, and packaging is separated for recycling.

Drawing set order of precedence is normally specification, then large-scale detail drawings, then general plans and elevations; a written dimension overrides a scaled measurement.

Scale reading: 1:100 means 1 mm on paper equals 100 mm real; a 25 mm line on a 1:50 detail represents 1250 mm on site.

Floor-to-floor height equals finished floor level to finished floor level; ceiling height is finished floor level to underside of ceiling lining or ceiling frame.

Levels are given as reduced levels in metres to three decimals (e.g. RL 12.450); a positive value is above the datum, a negative value below it.

Nominal versus actual sizes: a 90 mm stud is 90 x 35 mm nominal, while timber is dressed to smaller actual dimensions; framing centres are given as 450 or 600 mm.

A specification clause governs material, mix ratio, coat thickness and finish; where a drawing and specification conflict, request written clarification before proceeding.

Section and detail callouts use a reference bubble with sheet number and detail number; the arrow shows the direction of view.

Setting-out dimensions are checked by cross-referencing overall building dimensions against the sum of part dimensions; a mismatch indicates a drawing error.

Stainless steel trowel is used for final finishing because it closes and polishes the surface; a steel trowel brings moisture and fines to the face and can cause crazing if overworked.

Wood float leaves a keyed, open texture suitable for a subsequent coat; a sponge float closes the surface for a fine finish.

Hawk and trowel balance: the hawk is held flat under the work, and mortar is loaded on the trailing edge to reduce wrist strain.

Mixing paddle speed is kept low (around 400-600 rpm) to avoid entraining air; the drill should be variable speed with a paddle sized to the bucket.

Cleaning regime: tools are washed immediately after each mix, trowel edges are kept straight and burr-free, and blades are dried to prevent rust.

Render spray machines require daily cleaning of the rotor-stator, hopper and hose; a blocked hose is depressurised before any connection is loosened.

Straight edges, rules and screeds are checked for straightness and level before each use; a warped screed transfers error into the finished plane.

Electrical tools are tested and tagged at the interval set by the site regime, and leads are protected from damage and kept out of wet areas.

Background suction control: porous masonry is dampened or primed so the plaster does not dehydrate before set; high-suction backgrounds may need a bonding agent or PVA slurry.

Bonding agents: PVA is used as a sealer or bonding aid, but a PVA film must not be allowed to become a weak, re-emulsifiable layer in wet areas.

Key and mechanical grip: smooth concrete is scabbled, etched or spattered with a bonding coat so the first coat can grip mechanically.

Dot and screed: dots are set plumb and level at intervals, screeds are run between dots, and the plane is checked with a straight edge and level before floating.

Setting-out tolerance: a wall is checked for plumb and line with a level and straight edge; deviation is corrected in the base coat, not in the finish coat.

Beads and stops: angle beads protect external corners, stop beads terminate plaster at openings, and movement beads accommodate structural movement.

Moisture-sensitive backgrounds: gypsum plaster is not applied to a background with rising or penetrating damp; the source is rectified and the wall allowed to dry.

Metal lath and expanded mesh are fixed with the long dimension across supports and lapped as specified so the plaster keys through the mesh.

Gypsum plaster coats: a two-coat system is common, with the first coat (backing or floating coat) keyed and the finish coat applied at about 2-3 mm.

Mixing ratio: plaster is mixed to the manufacturer's water-to-powder ratio; adding extra water after initial set weakens the set and causes dusting.

Setting time: the plaster is worked while it is still green; once it stiffens it must not be retempered with water.

Ceiling work: plaster is applied in sections with the trowel drawn toward the body, and the scaffold platform is set so the operative can reach the full ceiling without over-reaching.

Corner and junction sequence: internal angles are finished with an internal corner trowel, and the second wall is worked before the first angle sets.

Curing and drying: fresh plaster is protected from draughts and direct heat, and the drying period before decoration follows the manufacturer's guidance.

Bonding coat: a spatter or slurry coat is applied and allowed to set before the plaster coat, providing a mechanical key on low-suction or smooth backgrounds.

Defect prevention: rapid drying causes crazing and shrinkage cracks; controlled, even drying and adequate background preparation reduce the risk.

Render mix: a common cement-lime-sand render is 1:1:6 cement:lime:sand by volume; stronger, richer mixes increase shrinkage and cracking risk.

Coat thickness: render coats are typically 8-10 mm, and total thickness over masonry is generally kept to around 15-20 mm unless designed otherwise.

Two-coat render: the scratch coat is scored to form a key, then the finish coat is applied after the first has set and cured.

Movement and control joints: joints are located at changes in substrate, at storey heights and at set spacings, and beads are fixed before rendering.

Curing: fresh render is protected from rapid drying and direct sun or wind; damp curing improves strength and reduces shrinkage cracking.

Salt and efflorescence: soluble salts migrate to the surface as moisture evaporates; the source of moisture is addressed and the deposit is brushed off dry.

Render over masonry: the background is cleaned, dampened and, where suction is high, primed so the mix retains water for hydration.

Weathertightness: flashings, weep holes and damp-proof courses are kept clear of render so water can drain from the wall cavity.

Veneer and skim coats are applied thin and worked with a trowel or sponge to produce a mottled or polished surface; the finish is built in layers.

Polished plaster effect depends on trowel pressure and timing: working the surface at the right stage of set compacts the material and raises sheen.

Stucco and rustic finishes use graded aggregates and coloured oxides; the colour is in the mix, so batch consistency must be maintained across the whole wall.

Decorative banding and mouldings are set out from a datum line, and templates or running moulds are guided by rules fixed to the wall.

Sample panels are approved before full application; the approved panel is retained on site as the benchmark for colour, texture and sheen.

Colour matching: pigments are measured by weight, not volume, and the same batch of pigment and binder is used for the whole elevation.

Texture tools include sponge, float, brush and trowel; the tool and its timing determine whether the finish is open, closed or dragged.

Protection of specialist finishes: adjacent surfaces are masked, and the finished face is protected from trades until fully dry.

Plumb and level tolerance: walls are checked with a 2 m straight edge and level, and the finish is accepted within the specified deviation, commonly a few millimetres over the length.

Crazing is a network of fine surface cracks from shrinkage; it is rectified by filling and refinishing, and prevented by controlled drying and correct mix.

Blistering or shelling is a loss of bond between coats; the area is cut back to sound material, the background is prepared, and the coat is reinstated.

Hollow or drummy plaster is detected by tapping; it is cut out to the sound edge, the background is keyed and primed, and the patch is filled and blended.

Efflorescence is treated by dry brushing and eliminating the moisture source; washing with water can drive salts back into the render.

Inspection stages: background preparation, beads and fixings, base coat, finish coat and final finish are each checked before the next stage covers them.

Clean-up: droppings are removed before they set, mortar is not washed into drains, and the work area is left clear of tools, packaging and waste at the end of each shift.

Records: batch numbers, mix ratios, sample approvals and inspection results are recorded so nonconformance can be traced to a cause.