Red Seal Lather (ISM) cheat sheet

Fall protection is required when working at heights of 3 m (10 ft) or more in most Canadian jurisdictions; guardrails, safety nets, or personal fall arrest systems must be used.

When using a personal fall arrest system, the anchorage point must support at least 22 kN (5,000 lb) per worker, and the free-fall distance must be limited to 1.2 m (4 ft) or less.

Scaffolding must be erected, altered, and dismantled only by a competent worker, and the platform must be at least 460 mm (18 in) wide with a guardrail system including top rail, mid rail, and toe board.

Ladders must be set up at a 1:4 ratio (75° angle) and extend at least 1 m (3 ft) above the landing; they must be secured and inspected before use.

Hazard communication (WHMIS 2015) requires that all controlled products have a supplier label and a safety data sheet (SDS) readily available; workers must be trained in their use.

Respiratory protection: for dust from gypsum board or plaster, use a NIOSH-approved N95 respirator; for silica dust from cutting cement board or stucco, use at least an N95 and consider wet-cutting or local exhaust ventilation.

Housekeeping: keep walkways clear, remove debris frequently, and store materials so they do not obstruct exits or create tripping hazards; use a dustpan or vacuum rather than dry sweeping to control dust.

Emergency procedures: know the location of first aid kits, fire extinguishers, and eye-wash stations; report all injuries and near misses immediately to the supervisor.

Personal protective equipment (PPE): safety glasses with side shields, hearing protection when using powder-actuated tools or high-noise equipment, and gloves when handling wire lath or metal framing.

In Canada, the National Building Code (NBC) is the model code; provinces adopt it with amendments. Always verify the local adopted edition and any municipal bylaws.

Fire-resistance ratings are expressed in hours (e.g., 1 h, 2 h) and are achieved by specific assemblies listed in the NBC or in manufacturer listings (e.g., UL/ULC, ULC).

Fire separations must be continuous from floor to underside of slab and be constructed to resist the passage of smoke and fire; penetrations must be sealed with listed firestop systems.

Sound transmission class (STC) ratings: for party walls between dwelling units, the NBC requires an STC of at least 50. Steel stud walls with sound insulation and resilient channels can achieve this.

When reading drawings, architectural plans show layout and dimensions; structural drawings show framing and load paths; mechanical and electrical drawings show services. Cross-reference all to avoid conflicts.

Specifications (Divisions 01–49) define material quality, execution, and submittals. Division 09 covers finishes (gypsum board, plaster, stucco).

Symbols and abbreviations: on architectural drawings, a dashed line often indicates an object above the cut plane (e.g., a soffit); a solid line indicates a visible object. Refer to the legend for specific symbols.

Building code requirements for gypsum board: used as a fire separation, it must be installed with the required thickness, fastener spacing, and joint treatment as per the listed assembly.

Vapour barrier code requirements: in cold climates, a vapour barrier with a permeance of 0.15 perm (8.5 ng/(Pa·s·m²)) or less is typically required on the warm side of insulation; verify local code.

Steel studs for interior partitions are typically spaced at 400 mm (16 in) or 600 mm (24 in) on centre; the spacing depends on the gypsum board thickness and the required fire-resistance rating.

When framing a partition, the floor and ceiling tracks must be fastened at maximum 600 mm (24 in) on centre; studs are cut 10 mm (3/8 in) shorter than the track-to-track height to allow for deflection.

For suspended ceilings, the main runners (carrying channels) are spaced at 1200 mm (4 ft) on centre, and cross tees are spaced at 600 mm (2 ft) or 400 mm (16 in) to support the ceiling panels.

Hanger wires for suspended ceilings must be 12-gauge (2.6 mm) soft annealed galvanized steel wire, spaced at maximum 1200 mm (4 ft) on centre along main runners, and within 150 mm (6 in) of the ends.

Furring channels for plaster or gypsum board are spaced at maximum 400 mm (16 in) on centre for walls and 400 mm (16 in) for ceilings unless the manufacturer's instructions specify otherwise.

Resilient channels (RC) are used to decouple gypsum board from framing to improve acoustics; they are spaced at 400 mm (16 in) or 600 mm (24 in) on centre, and must be installed perpendicular to the studs.

Control joints in gypsum board ceilings are required for large areas: maximum 9.3 m² (100 sq ft) per joint in ceilings, and at maximum 9.1 m (30 ft) intervals; follow manufacturer's recommendations.

When installing a suspended ceiling, the border panels should be at least half the width of a full panel; avoid narrow strips by adjusting the main runner layout.

Wood furring strips must be at least 19 mm x 38 mm (1 in x 2 in) nominal, spaced at maximum 400 mm (16 in) on centre, and fastened with appropriate anchors to the substrate.

Exterior finishes such as stucco must be installed over a weather-resistive barrier (WRB) and a drainage plane; the WRB must be lapped shingle-fashion and taped at seams.

Interior wall finishes: gypsum board joints must be taped and treated with joint compound; the level of finish (Level 1 to Level 5) is specified according to the appearance requirements (e.g., Level 5 for glossy paint under critical lighting).

When applying veneer plaster, the basecoat is applied over a special plaster base (blue board) and the finish coat is applied after the basecoat has set; total thickness is typically 3 mm (1/8 in).

For exterior stucco, a minimum of three coats is standard: scratch coat, brown coat, and finish coat; each coat must be cured and scored appropriately.

Ceiling finishes: when installing gypsum board on ceilings, use ceiling board (sag-resistant) for areas with high humidity or where required; fasteners must be driven so the heads are just below the surface without breaking the paper.

Acoustic ceiling panels: lay-in panels are installed in a grid; panels must be acclimatized to the room conditions for at least 24 hours before installation to prevent warping.

Corner bead must be installed on all external corners of gypsum board; it is fastened at maximum 150 mm (6 in) on centre and provides a straight, reinforced corner.

Trim accessories: use J-trim or L-trim at edges where gypsum board terminates; use control joints to relieve stress in large ceiling areas.

Gypsum board is available in thicknesses of 6.4 mm (1/4 in), 9.5 mm (3/8 in), 12.7 mm (1/2 in), 15.9 mm (5/8 in), and 19 mm (3/4 in); the most common for walls is 12.7 mm (1/2 in), and for fire-rated assemblies 15.9 mm (5/8 in).

Fastener spacing for gypsum board: on ceilings, screws are spaced at maximum 300 mm (12 in) on centre; on walls, maximum 400 mm (16 in) on centre. Fasteners must be driven to dimple the paper without breaking it.

When installing gypsum board on walls, boards should be applied vertically (parallel to studs) unless the wall height requires horizontal application; joints must be staggered between layers.

For fire-rated assemblies, the type and spacing of fasteners, the type of gypsum board (Type X), and the joint treatment must exactly match the listed assembly (e.g., ULC design).

Sheathing: exterior gypsum sheathing is water-repellent and must be covered with a WRB; plywood or OSB sheathing must be installed with a 3 mm (1/8 in) gap between panels for expansion.

When installing gypsum board over a vapour barrier, avoid puncturing the vapour barrier with fasteners; use adhesives or fasteners that do not penetrate the barrier where required.

Cutouts for electrical boxes: use a router or keyhole saw to cut openings; the opening should be no larger than necessary, and the box must be sealed to the gypsum board with an approved sealant in fire-rated assemblies.

Backing for gypsum board: all edges must be supported by framing or a backing board; cantilevered edges are not permitted unless designed.

Vapour barrier placement: in cold climates, the vapour barrier must be installed on the warm side of the insulation (interior side). In Canada, a polyethylene sheet of at least 0.15 mm (6 mil) is commonly used.

Air barrier requirements: the air barrier must be continuous across the building envelope, including at penetrations, joints, and intersections. It must be sealed with compatible sealants or tapes.

Batt insulation: install without gaps or compression; compression reduces R-value. For example, compressing a nominal R-12 batt by 50% can reduce its R-value by nearly half.

Blown-in insulation: must be installed to the specified density and thickness to achieve the required R-value; use depth markers to ensure uniform coverage.

Rigid foam insulation: when used on the exterior, it can serve as sheathing and must be covered with a WRB if required; joints must be taped to provide a continuous air barrier.

Vapour barrier sealing: all seams and penetrations must be sealed with an approved tape (e.g., red sheathing tape) or acoustical sealant. Use acoustical sealant at the perimeter and at electrical boxes.

In cathedral ceilings, provide ventilation channels above the insulation to prevent moisture buildup; a minimum 25 mm (1 in) air space is recommended.

When installing insulation around electrical boxes, maintain the required clearance from heat sources (e.g., recessed light fixtures) as per the manufacturer's instructions and code.

Metal lath: diamond mesh lath is available in weights of 1.75 lb/yd² and 2.5 lb/yd²; it must be fastened to framing with approved fasteners at maximum 150 mm (6 in) on centre.

Plaster basecoat: for gypsum plaster, a basecoat of 10 mm (3/8 in) is applied over lath, followed by a finish coat of 3 mm (1/8 in).

Stucco: the scratch coat is 10 mm (3/8 in) thick, the brown coat is 6 mm (1/4 in) thick, and the finish coat is 3 mm (1/8 in) thick; total thickness is at least 19 mm (3/4 in).

Curing: stucco must be moist-cured for at least 48 hours after the scratch coat and 48 hours after the brown coat; avoid rapid drying.

Lath accessories: use casing beads at edges, corner aid at corners, and control joints to relieve stress; control joints are spaced at maximum 3 m (10 ft) in stucco.

For three-coat stucco, the scratch coat must be scored (horizontal lines) to provide a mechanical key for the brown coat.

Plaster mixes: gypsum plaster sets by chemical hydration; do not add accelerators or retarders unless specified. Use clean water and mix to the manufacturer's proportions.

When applying plaster over a gypsum board base (veneer plaster), use a special plaster base board (blue board) and apply a bond agent if required.

Powder-actuated tools: only trained and certified operators may use them; wear eye and hearing protection, and never use in an explosive atmosphere.

When using a drywall screw gun, adjust the depth setting so the screw head dimples the paper without breaking it; replace worn bits regularly.

Cutting gypsum board: use a utility knife to score the paper and snap the board; for curves, use a keyhole saw or a drywall saw.

Mixing plaster or joint compound: use a heavy-duty drill with a mixing paddle; mix at low speed to avoid air entrainment, and allow the mix to slake before final mixing.

Tool maintenance: clean tools after each use; joint compound and plaster can harden and damage tools. Lubricate moving parts on screw guns and hoists as per the manufacturer.

Scaffolding and work platforms: inspect before use; ensure all locking pins are engaged and guardrails are in place. Do not use damaged equipment.

Ladders: inspect for cracks, missing feet, or damaged rungs; never use a ladder that is not rated for the load. Maintain three points of contact when climbing.

Dust control: use a vacuum with a HEPA filter when sanding joint compound or cutting gypsum board to reduce airborne dust.

Estimating gypsum board: calculate the total square footage of the area to be covered, then divide by the square footage of a sheet (e.g., 4 ft x 8 ft = 32 sq ft). Add 10% for waste.

Estimating joint compound: approximately 1 kg (2.2 lb) of joint compound is needed per 1 m² (10.8 sq ft) of gypsum board for a Level 4 finish.

Estimating screws: approximately 30 screws per 4 ft x 8 ft sheet (32 sq ft) for walls, and 40 for ceilings.

Material handling: store gypsum board flat on a level surface and support it at maximum 400 mm (16 in) on centre to prevent sagging. Keep materials dry and off the floor.

Site preparation: before installing finishes, ensure the substrate is clean, dry, and free of dust, oil, or loose material. Verify that framing is straight and plumb within tolerance (typically 3 mm in 2.4 m).

Acclimatization: allow gypsum board and other materials to acclimatize to the room temperature and humidity for at least 24 hours before installation.

Waste management: separate recyclable materials (e.g., clean gypsum board, metal studs) from general waste; follow local recycling guidelines.

Estimating insulation: calculate the area to be insulated and divide by the coverage per bag (e.g., a bag of blown-in insulation covers a specific area at a given R-value).