Red Seal Drywall Finisher & Plasterer cheat sheet

Hierarchy of controls, most to least effective: elimination, substitution, engineering controls, administrative controls, personal protective equipment.

Silica: crystalline silica in joint compound, plaster, and stucco dust is a designated carcinogen; wet methods and HEPA-equipped dust extraction are engineering controls, a respirator is the last line.

Respirable crystalline silica exposure limit under US OSHA 29 CFR 1926.1153 is an 8-hour TWA of 50 µg/m³; Table 1 tasks specify control methods instead of air monitoring.

Asbestos is presumed present in joint compound, texture coats, and floor tile adhesive in buildings built before the mid-1980s; stop work and test before disturbing.

Lead paint is presumed in pre-1978 housing; disturbance triggers lead-safe work practices and containment.

Fall protection is required at 3 m (10 ft) in general construction and at lower heights on scaffolds; guardrails, personal fall arrest, or a positioning system.

Scaffold and stilts: stilts raise working height, so overhead clearance, doorway height, and floor condition must be checked; stilts are not permitted on scaffolds or on surfaces with openings.

Abrasive blasting and sanding of plaster require eye, hearing, and respiratory protection; noise above 85 dBA over 8 hours requires a hearing conservation program.

Waste segregation: gypsum board scrap is recyclable but must be kept dry and free of joint compound and paper-faced contaminants; solvents, lead paint debris, and asbestos waste are separate streams.

Gypsum board thickness selection: 12.7 mm (1/2 in) for standard walls, 15.9 mm (5/8 in) for ceilings at 600 mm (24 in) framing and for fire-rated assemblies, 9.5 mm (3/8 in) for curved work.

Joint compound types: taping (setting-type or all-purpose) for embedding tape, topping for finish coats, and pre-mixed lightweight for sanding ease; setting compounds cure chemically and are not affected by drying.

Setting compound set times are labelled 20, 45, 90, or 210 minutes; shorter times suit rapid multi-coat work but cannot be retempered after set.

Corner bead types: nail-on, screw-on, paper-faced (with laminated flanges), and bullnose; paper-faced bead is preferred for straight, crack-resistant corners.

Stucco: Portland cement-based scratch and brown coats, lime for workability, and acrylic or elastomeric finish coats; fiber mesh replaces some lath in some systems.

Lath: metal lath (diamond mesh) weighs about 2.5 lb/yd² (1.4 kg/m²) for 3/8 in rib and 3.4 lb/yd² for flat; self-furring lath provides a key space behind the mesh.

Taping tools: automatic taper, bazooka, corner roller and finisher, and flat box; automatic tools require compound of the correct viscosity, typically thinner than hand-taping mud.

Sanding: pole sander with 100–150 grit for compound, finer for finish coats; over-sanding fuzzes paper and creates a visible halo under paint.

Drawing order of precedence: written specifications and addenda typically govern over drawings; large-scale detail drawings govern over small-scale plans; figured dimensions govern over scaled measurements.

Wall type schedules correlate partition types (e.g., fire-rated, acoustic, shaftwall) with layer build-up, stud spacing, and board thickness; the schedule governs the assembly.

Fire-resistance ratings are expressed in hours (1 h, 2 h) and correspond to tested assemblies; the listed components cannot be substituted without an engineering judgment.

Ceiling height and soffit dimensions are taken from reflected ceiling plans and sections; check grid layouts for light fixtures and diffusers before framing.

Control joints, expansion joints, and construction joints are shown on the architectural drawings; their location and spacing are design requirements, not field choices.

Layout: establish a baseline and square the area using the 3-4-5 method or diagonals; check that partition dimensions match the dimension strings and not the scaled drawing.

Finish schedules list the finish system by room (e.g., level 4 gypsum board, skim coat plaster, trowel texture); the level of finish governs the number of coats and sanding.

Specifications for stucco include the weather-resistive barrier, lath attachment, and the number of coats; three-coat work is standard for exterior Portland cement stucco.

Framing tolerances: studs should not vary more than 3 mm (1/8 in) from the plane of adjacent studs; excessive variation is corrected with shims or sistering before board goes up.

Backing is required at all board edges that are not supported by framing: corners, ceiling perimeters, and openings; blocking is installed before boarding.

Substrate moisture: wood framing should be at or below 19% moisture content; concrete and masonry should be dry and free of form release agents before plaster or adhesive.

Dust, oil, and loose material must be removed from substrates; bond failure from dust is a common cause of blistering in veneer plaster.

Concrete surfaces for direct-applied plaster need a bonding agent or mechanical key (scarification) unless the surface is rough and absorptive.

Metal studs: check for plumb, alignment, and secure attachment; screws must not be overdriven through the stud flange, which reduces pull-out.

Existing substrates in renovation: test for asbestos, lead, and moisture; a moisture meter reading above 15–20% in wood framing indicates a leak or drying problem to resolve first.

Vapour barrier placement: on the warm side of the assembly in cold climates; in mixed climates, a vapour-retarder paint may be used instead.

Ventilation and drying: new plaster and joint compound release water; the space should be ventilated and above 10 °C (50 °F) during curing.

Fastener spacing: screws at 300 mm (12 in) on ceilings and 400 mm (16 in) on walls for single-layer board; 200 mm (8 in) on ceilings for fire-rated and water-resistant assemblies.

Screw length: board thickness plus at least 16 mm (5/8 in) penetration into wood framing, or at least 10 mm (3/8 in) past the metal stud flange.

Screws are driven so the head is slightly below the board surface without breaking the paper; dimpled, not torn, is the target.

Board orientation: horizontal application with joints offset from the framing and from the opposite side; staggered end joints reduce cracking.

Joints: butt joints should be backed and offset from adjacent courses; tapered edges allow a recessed joint for taping.

Curved work: 6.4 mm (1/4 in) board for tight radii, 9.5 mm (3/8 in) for moderate radii; dampening or scoring the back improves bending.

Water-resistant board is required in wet areas (tub surrounds, shower walls) but is not a substitute for a waterproof membrane in shower pans and steam rooms.

Fire-rated assemblies: use the specified board type and thickness, fastener type and spacing, and joint treatment; any deviation voids the rating.

Acoustic assemblies: resilient channel, insulation, and double-layer board with staggered joints; sealant at perimeters reduces flanking sound.

Joint compound shrinkage: setting-type compounds shrink less than drying-type; use setting compound for the first coat and for filling large voids.

Tape embedding: paper tape is embedded in a thin bed of compound and the excess is squeezed out; bubbles and blisters must be cut out and re-taped.

Coat sequence: embed tape, then a fill coat, then a finish coat; each coat is wider than the previous, typically 50 mm (2 in) per side.

Finish levels: Level 1 for plenum and service areas; Level 2 for tile and behind cabinets; Level 3 for heavy texture; Level 4 for flat paint; Level 5 for gloss paint and critical lighting.

Level 5 requires a skim coat over the entire surface; it is specified where gloss or semi-gloss paint and critical lighting will reveal imperfections.

Sanding: sand between coats with light pressure; over-sanding exposes tape edges and paper fuzz, which shows through paint.

Corner treatment: coat both sides of an inside corner at once and feather the edges; outside corners use corner bead and are coated on both faces.

Priming: use a drywall primer before finish paint; bare compound absorbs paint unevenly and causes flashing.

Inspection: check joints under raking light at a shallow angle; imperfections invisible under direct light become visible under glancing light.

Three-coat plaster: scratch coat, brown coat, and finish coat; the scratch coat is scored to key the brown coat, and the brown coat is floated to establish the plane.

Gypsum plaster base coats over gypsum lath: the scratch coat is about 6 mm (1/4 in) and the brown coat brings total thickness to about 12 mm (1/2 in).

Portland cement stucco: scratch coat 6–10 mm (1/4–3/8 in), brown coat 6–10 mm, finish coat 3–6 mm (1/8–1/4 in); total thickness about 20 mm (3/4 in) over lath.

Grounds: screeds and grounds establish thickness and plane; wood or metal grounds are set at corners, openings, and floor lines before plastering.

Metal lath must be lapped at least 13 mm (1/2 in) at sides and 25 mm (1 in) at ends, and fastened at 150 mm (6 in) on center; self-furring lath keeps a key space.

Lath over wood studs requires building paper or a weather-resistive barrier behind the lath to prevent moisture damage and to provide a bond break.

Curing: Portland cement stucco must be kept damp for at least 48 hours after each coat, and protected from freezing; rapid drying causes shrinkage cracking.

Bonding agents and keys: plaster over masonry requires a mechanically keyed or scarified surface, or a bonding agent; smooth concrete needs both.

Accelerators and retarders adjust set time; calcium chloride accelerates set but can cause efflorescence and corrosion, so its use is restricted.

Veneer plaster: a thin 2–3 mm (1/16–1/8 in) gypsum finish applied over a special base board; it cures hard and gives a monolithic surface.

Skim coating: thin coats of joint compound or veneer plaster applied over the whole surface to level it; required for Level 5 and for renovation over damaged board.

Texture types: orange peel, knockdown, and acoustic (popcorn); knockdown is applied as a thinned compound, partially set, then flattened with a trowel.

Acoustic texture is applied to ceilings and must not bridge fire-rated assemblies or cover sprinkler heads and smoke detectors.

Mouldings: crown, casing, base, chair rail, and picture mould; joints are coped at inside corners and mitred at outside corners.

Crown moulding spring angles (typically 38° and 52°) determine the mitre and bevel settings on a mitre saw; wrong spring angle causes open joints.

Plaster mouldings are cast or run in place with a template; running in place requires a straight, plumb backing and a guide screed.

Decorative finishes: Venetian plaster (lime-based, burnished), lime wash, and faux finishes; each has its own cure and sealing requirements.

Sealants: paintable acrylic-latex sealant at movement joints and trim, and silicone in wet areas; sealant must be compatible with the finish coat.

Weather-resistive barrier (WRB): building paper (Grade D) or a house wrap is installed over sheathing with laps of at least 50 mm (2 in) and is shingled so water drains outward and downward.

Flashing: kick-out flashings, sill pans, and head flashings must integrate with the WRB; stucco terminates above flashings with a weep screed.

Weep screed: required at the base of stucco walls and at the foundation; it provides drainage and a minimum clearance of 100 mm (4 in) above grade or 50 mm (2 in) above paved surfaces.

Control joints in stucco: spaced no more than about 3 m (10 ft) in each direction, and at changes in substrate, corners of openings, and floor lines.

Casing bead and corner aid provide straight edges and movement accommodation at openings and corners.

Two-coat and three-coat systems: three-coat over metal lath is standard for wood-frame construction; one-coat systems use a proprietary fiber-reinforced base.

Curing and weather: stucco must not be applied below 4 °C (40 °F) or in direct sun and wind without protection; freezing before set destroys the coat.

Efflorescence is salt migration from moisture; it is removed with a dilute acid wash after the wall is dry, and the moisture source must be corrected.

Drainage plane: a drained and ventilated assembly uses a WRB plus a drainage mat or furring to keep the stucco off the sheathing.

Patch sequence: remove loose material to sound substrate, prime the edges, fill in thin layers, and feather the patch into the surrounding plane.

Plaster repair: use a patching plaster or setting compound that matches the original hardness; hard patching compound over soft gypsum plaster causes cracking at the interface.

Keys and lath: where plaster has lost its key, reattach with plaster washers or cut out and replace the section; simply filling over a loose area will fail.

Water damage: identify and correct the source before repair; staining may be sealed with a stain-blocking primer, but wet substrate must dry first.

Matching texture: use a test panel to match the existing texture; the same compound, nozzle, and technique must be used to match orange peel or knockdown.

Historic plaster: lime-based plaster is softer and more vapour-permeable than gypsum; repairs should use compatible materials to avoid trapping moisture.

Fire and smoke damage: seal with a shellac or oil-based stain-blocking primer after cleaning; water-based primers may not seal odour.

Renovation sequencing: demolition, substrate repair, framing changes, boarding, taping, then finish; dust containment and negative air are used in occupied buildings.

Documentation: photograph existing conditions before repair; the record supports warranty and change-order claims.