Materials, Fasteners, and Support Systems

Materials, Fasteners, and Support Systems

Chapter Introduction

This chapter covers all the materials, fasteners, and support systems that the lather (interior systems) must master for the Red Seal exam. You must not only know the products, but also understand why they are used, how they interact with each other, and which rules of the National Building Code (NBC) and the Canadian Electrical Code (CE Code) apply. Selecting the wrong material or an inadequate fastener is a common cause of assembly failure, partition breakage, or non-compliance with fire-resistance requirements. This chapter prepares you to answer exam questions on informed selection, load calculations, and code application.

2.1 Metals Used in Lathing and Interior Systems

2.1.1 Galvanized Steel

Galvanized steel is the base material for furring channels, studs, tracks, and hangers. Galvanization (zinc coating) protects against corrosion. For interior systems, a galvanization class of G40 (0.40 oz/ft²) to G60 (0.60 oz/ft²) is typically used. G60 is required in humid environments (bathrooms, pools, laundry rooms).

Mechanical characteristics:

2.1.2 Aluminum

Aluminum is used for finishing profiles (edge trims, corners) and certain suspended ceiling systems. It is lighter than steel, resists corrosion, but is softer and more expensive. It must never be in direct contact with galvanized steel in the presence of moisture (galvanic corrosion). An insulator (tape, paint) must separate the two metals.

2.1.3 Stainless Steel

Reserved for special applications: corrosive environments (chemical plants, coastal areas) and exposed fasteners where aesthetics matter. Type 304 or 316 stainless steel screws and bolts are used with stainless steel profiles.

2.2 Profiles and Support Components

2.2.1 Studs

Studs are C-shaped (or U-shaped) profiles that form the vertical framework of partitions. They are manufactured from galvanized steel by cold forming.

Spacing rule: Stud spacing is 400 mm (16 in) or 600 mm (24 in) on center. 400 mm spacing is required for 1-hour or greater fire-rated partitions, and for tiled walls. 600 mm spacing is permitted for non-load-bearing partitions with 12.7 mm (1/2 in) or thicker gypsum board.

2.2.2 Tracks

Tracks are U-shaped profiles that receive the studs at the top and bottom. They have the same width as the corresponding studs. The track must be at least the same thickness as the stud. The track length must extend at least 150 mm beyond the last stud at each end, or be anchored to an adjacent structural element.

2.2.3 Furring Channels

Furring channels are Z-shaped or hat-shaped profiles used for:

Z-shaped furring channels are fastened directly to the structure. Hat channels are used with hangers to create a service space. The maximum spacing of furring channels is 400 mm for 12.7 mm gypsum board and 600 mm for 15.9 mm (5/8 in) gypsum board installed perpendicularly.

2.2.4 Hangers

Hangers are threaded rods (suspension rods) or steel wires that support the furring channels or tracks of a suspended ceiling.

NBC Rule (9.29.5.3): Hangers must be spaced no more than 1200 mm apart along the furring channels, and furring channels must be spaced no more than 1200 mm apart from each other. The distance between the closest hanger and the wall must not exceed 150 mm.

2.2.5 Hanger Clips

Clips connect the hanger to the furring channel or track. Common types:

The allowable load of each clip must be verified. An improperly installed clip (not fully engaged) is a common cause of ceiling collapse.

2.3 Sheathing Materials

2.3.1 Gypsum Board

Gypsum board is the most common sheathing material. It consists of a core of calcium sulfate dihydrate (CaSO₄·2H₂O) encased in recycled paper.

Type X properties: Type X contains glass fibers and additives that maintain the panel's integrity under heat. It provides a 1-hour fire-resistance rating for a single layer of 15.9 mm board on 92 mm studs spaced at 400 mm.

Installation rule (NBC 9.29.5.8): Gypsum board must be installed perpendicular to studs or furring channels, with joints staggered by at least 200 mm between adjacent rows. Screws must be spaced 300 mm on center on studs and 400 mm on center on furring channels.

2.3.2 Cement Board

Used in wet areas (showers, saunas, countertops). They do not deteriorate in the presence of water. Common thicknesses: 12.7 mm and 15.9 mm. They are cut using a grinder or a carbide-tipped knife. Screws must be stainless steel or galvanized with countersunk heads, spaced 200 mm on center.

2.3.3 Gypsum Fiber Panels

Denser than regular gypsum board, they offer better impact and moisture resistance. Used for stairwell walls and shaft walls. They are fastened with self-drilling screws and cut with a jigsaw or circular saw with a carbide blade.

2.3.4 Acoustic Panels (Suspended Ceilings)

Suspended ceiling panels (tiles) are made of mineral fiber, fiberglass, or gypsum. Their acoustic performance is measured by the NRC (Noise Reduction Coefficient) and CAC (Ceiling Attenuation Class). An NRC of 0.70 means that 70% of incident sound energy is absorbed.

2.4 Fasteners

2.4.1 Drywall Screws

Drywall screws are self-drilling screws with countersunk heads (Phillips or Torx) and an aggressive thread.

Penetration rule: The screw must penetrate at least 10 mm into the steel stud or wood. The head must be countersunk 1 to 2 mm below the board surface, without tearing the paper.

2.4.2 Nails

Nails are used for attaching gypsum board to wood only. They must be ring-shank or spiral to improve pull-out resistance. The maximum spacing is 200 mm on studs and 150 mm on edges. Nails are rarely used in modern commercial systems, but the exam may test you on their limitations.

2.4.3 Anchors

To fasten tracks or hangers to concrete or masonry, the following are used:

Important rule: The minimum anchor depth in concrete is 25 mm for wedge anchors and 30 mm for concrete screws. The hole must be drilled perpendicular to the surface, and dust must be blown out before insertion.

2.4.4 Bolts and Nuts

Used for structural assemblies (ceiling hangers, track supports). Bolts must be Grade 2 or higher, with washers under the head and nut. The threads must extend at least 2 threads beyond the nut.

2.5 Load and Spacing Calculations

2.5.1 Linear Load on a Hanger

The load on a hanger is calculated as follows:

Load = (area supported by the hanger) × (ceiling weight per m²)

Example: Suspended ceiling of 12.7 mm gypsum board (weight ≈ 8 kg/m²) with furring channels spaced at 600 mm and hangers spaced at 1200 mm.

Area supported by one hanger = 0.6 m × 1.2 m = 0.72 m²

Load = 0.72 m² × 8 kg/m² = 5.76 kg ≈ 56 N

This load is well below the capacity of a 6 mm threaded rod (450 N). But if you add insulation (5 kg/m²) and accessories (2 kg/m²), the total load becomes 15 kg/m², or 10.8 kg per hanger. You must always verify the capacity of the hanger and the clip.

2.5.2 Number of Screws per Board

For a 1.2 m × 2.4 m (2.88 m²) gypsum board fastened to studs spaced at 400 mm:

2.5.3 Calculating Stud Length

Stud length = partition height − 2 × track height (typically 25 mm each).

For a 3.0 m partition with 25 mm tracks:

Stud length = 3000 mm − 50 mm = 2950 mm

The stud must be inserted into the track with a 6 mm clearance at the top to allow for thermal expansion and building movement.

2.6 Applicable Codes and Standards

2.6.1 National Building Code (NBC)

The NBC is the primary reference for interior systems. The relevant sections:

Rule 9.29.5.2: Gypsum board must be fastened so that joints do not coincide with the edges of openings (doors, windows).

Rule 9.30.1.2: Suspended ceilings must be designed to support their own weight plus an additional load of 0.25 kPa (25 kg/m²) for maintenance.

2.6.2 Canadian Electrical Code, Part I

The CE Code, Part I (CSA C22.1) applies to electrical installations, but the lather must know the rules regarding space for electrical boxes and cables:

Rule 8-200: Electrical boxes must be accessible. The lather must never cover a junction box without ensuring a cover is installed and accessible.

Rule 12-100: Cables must be supported at intervals of no more than 1.5 m and within 300 mm of each box. The lather must provide openings in studs for cable passage.

2.6.3 CSA B149.1 (Natural Gas and Propane Code)

Although this code concerns gas installers, the lather must know that gas pipes must not be embedded in partitions without protection. Rule 6.3.1 requires gas pipes to be accessible or protected against corrosion.

2.6.4 ASTM and CAN/CGSB Standards

2.7 Installation Procedures

2.7.1 Track Installation

2.7.2 Stud Installation

2.7.3 Ceiling Furring Channel Installation

2.7.4 Gypsum Board Installation

2.8 Special Support Systems

2.8.1 Fire-Rated Partitions

Fire-rated partitions are rated in hours (1 h, 2 h, 3 h). Components must conform to the tested assembly (ULC, Intertek). Key rules:

2.8.2 Acoustically Rated Ceilings

To achieve a high STC (Sound Transmission Class) rating:

2.8.3 Shaft Walls

Shaft walls for ventilation ducts, pipes, and cables use specific systems:

2.9 Common Errors and Inspections

2.9.1 Frequent Installation Defects

2.9.2 Mandatory Inspection Points

Before closing a partition, verify:

2.10 Practical Calculations for the Exam

2.10.1 Number of Gypsum Boards

For a room measuring 4 m × 5 m with a height of 2.7 m:

Wall area = 2 × (4 + 5) × 2.7 = 48.6 m²

Area of one board = 1.2 × 2.4 = 2.88 m²

Number of boards = 48.6 / 2.88 = 16.9 → 17 boards (round up)

Add 5 to 10% for waste (cut-offs, errors): 18 to 19 boards.

2.10.2 Number of Screws

For the same project, with studs spaced at 400 mm:

Screws per board = 38 (calculated earlier)

Total number of screws = 17 boards × 38 screws = 646 screws

Add 10% for waste: 710 screws (a box of 1000 is recommended)

2.10.3 Length of Furring Channels

For a 4 m × 5 m ceiling with furring channels spaced at 600 mm:

Number of rows = 4 m / 0.6 m = 6.67 → 7 rows

Total length = 7 rows × 5 m = 35 m

Add 5% for cuts: 37 m of furring channels

Summary

Traps to Avoid