Wall Tile Installation

Chapter Introduction

Wall tile installation is a distinct field from flooring, with its own structural, moisture, and thermal requirements. For the Red Seal exam, you must master not only installation techniques, but also surface calculations, substrate selection criteria, waterproofing requirements, and applicable Canadian standards. This chapter covers all the skills assessed for installing tile on interior and exterior walls, including fastening systems, differential movement, control joints, and finishes.

2. Substrates and Surface Preparation

2.1 Types of Wall Substrates

The substrate is the surface on which tiles are installed. Its condition determines the durability of the installation. Common wall substrates are:

Substrate	Characteristics	Typical Use
Gypsum board (drywall)	Smooth surface, low cost, limited moisture resistance	Dry interior walls (living room, bedroom)
Cement board (e.g., Durock, WonderBoard)	Water-resistant, stable, does not warp	Showers, bathtubs, exterior walls
Masonry (concrete block, brick)	Irregular surface, variable absorption	Exterior walls, basements
Rigid foam board (e.g., XPS, polyiso)	Thermal insulation, low load-bearing capacity	Exterior walls (requires lathing)
Exterior plywood	Stable if properly fastened, not suitable for wet areas	Dry interior walls, low-humidity areas

Key Requirement: The substrate must be clean, dry, free of dust, grease, wax, and loose particles. A contaminated surface reduces adhesion by 50% or more, even with high-quality thin-set mortar.

2.2 Gypsum Board Preparation

Gypsum boards must be installed in accordance with manufacturer requirements and building standards. For wet areas (showers, bathtubs), standard gypsum board is not acceptable. Use cement board or moisture-resistant gypsum board (Type X) with a waterproofing membrane.

Preparation Procedure:

13.Check the wall for plumb with a 2 m level (tolerance: 3 mm over 2 m).

14.Fill joints between boards with mesh tape and joint compound (for dry areas) or thin-set mortar (for wet areas).

15.Allow to dry completely (24 to 48 hours depending on relative humidity).

16.Apply a liquid waterproofing membrane (e.g., RedGard, Hydro Ban) over the entire surface in wet areas, following manufacturer instructions (generally 2 cross-coats).

2.3 Cement Boards

Cement boards are the substrate of choice for showers and exterior walls. They are composed of Portland cement, sand, and reinforcing fibers, offering excellent moisture and impact resistance.

Installation:

Fasten boards with countersunk stainless steel or galvanized screws, spaced 150 mm on center into studs.

Leave a 3 mm gap between boards (control joint).

Fill joints with thin-set mortar and fiberglass mesh tape.

Edges must be supported by studs or blocking.

Caution: Cement boards are not waterproofing membranes. They must be covered with a liquid membrane or sheet membrane in areas of direct water exposure.

2.4 Lathing for Exterior Walls

For exterior masonry or foam board walls, metal lathing (mesh) is required to support the mortar. The lath must be fastened with corrosion-resistant fasteners, spaced 150 mm on center, with a 75 mm overlap at joints.

Types of Lath:

Welded wire mesh (e.g., 1.4 mm diameter, 50 mm mesh)

Fiberglass mesh (for low-impact areas)

3. Mortars and Adhesives

3.1 Classification of Thin-Set Mortars

Thin-set mortars are classified according to ANSI A118.1 (adopted in Canada) and CSA A23.1 for concrete. For the exam, remember the following types:

Type	Characteristics	Use
Thin-set mortar	Portland cement + fine sand + additives	Ceramic, porcelain, natural stone tile
Medium-bed mortar	Coarser sand, thickness 6 to 19 mm	Large-format tile, irregular surfaces
Organic adhesive (mastic)	Resin-based, short open time	Small wall tiles in dry areas
Thick-set mortar	Sand + cement, thickness 12 to 25 mm	Exterior walls, pools, high-traffic areas

Rule of Thumb: For tiles larger than 300 mm on any side, use a high-performance thin-set mortar (improved grade) with an adhesion of at least 1.0 MPa after 28 days.

3.2 Open Time and Adjustment Time

Open time: the period during which the mortar remains tacky after application. It ranges from 15 to 30 minutes depending on type and temperature.

Adjustment time: the period during which the tile can be adjusted after placement. Generally 10 to 15 minutes.

Exam Trap: Never exceed the open time. If the mortar forms a skin (dry film), remove it and reapply. Setting tile on skinned-over mortar reduces adhesion by 80%.

3.3 Calculating Mortar Quantity

Thin-set mortar consumption is expressed in kg/m². It depends on trowel size and tile format.

Formula: Quantity (kg) = Area (m²) × Consumption (kg/m²)

Tile Format	Recommended Trowel	Consumption (kg/m²)
Up to 100 mm	6 mm (V-notch) trowel	2.5 – 3.0
100 – 300 mm	10 mm (V-notch) trowel	3.5 – 4.5
300 – 600 mm	12 mm (square-notch) trowel	5.0 – 6.5
Over 600 mm	15 mm (square-notch) trowel	7.0 – 9.0

Calculation Example: For a 12 m² shower with 300 mm tiles, 10 mm trowel, consumption 4.0 kg/m²:

Quantity = 12 m² × 4.0 kg/m² = 48 kg of thin-set mortar.

Add 10% for waste: 48 × 1.10 = 52.8 kg.

4. Installation Techniques

4.1 Thin-Set Method

This is the most common method for interior walls. It involves applying mortar to the substrate with a notched trowel, then pressing the tile into the mortar.

Procedure:

52.Apply mortar over an area of approximately 1 m² (no more than you can cover within the open time).

53.Hold the trowel at a 45° angle to the wall to create uniform ridges.

54.Set the tile and apply firm pressure with a slight sliding motion.

55.Check alignment with spacers (spaced 2 to 3 mm for walls).

56.Use a level to check for plumb and flatness.

Coverage Requirement: For interior walls, mortar coverage must be at least 80% of the tile surface. For wet areas (showers) and exterior walls, coverage must be 95% or greater.

4.2 Thick-Set Method

Used for exterior walls, pools, and highly irregular surfaces. Mortar is applied in a thick layer (12 to 25 mm) over metal lath.

Procedure:

61.Fasten metal lath to the wall with corrosion-resistant fasteners.

62.Apply a first coat of mortar (scratch coat) 10 mm thick, leaving a rough texture.

63.Allow to cure for 24 hours.

64.Apply the final coat (brown coat) 10 to 15 mm thick, leveling with a straightedge.

65.Set tiles in fresh mortar or after curing using thin-set mortar.

Advantage: This system absorbs building movement and corrects substrate flatness defects.

4.3 Diagonal and Herringbone Installation

Diagonal installation (at 45°) is common for decorative walls. It requires more cuts and increases installation time by 15 to 20%.

Cut Calculation: For diagonal installation, border tiles are cut into triangles. The cut length equals the tile diagonal: D = L × √2, where L is the tile length.

Example: 300 mm × 300 mm tile. Diagonal = 300 × 1.414 = 424 mm.

4.4 Movement Joints

Movement joints (or control joints) are essential to allow for thermal and moisture expansion and contraction. They must be placed:

At changes in plane (inside and outside corners).

Every 6 to 8 linear meters on walls.

At junctions with floors, ceilings, and door frames.

In the corners of showers and bathtubs.

Joint Width: 6 to 12 mm, filled with a flexible sealant (e.g., silicone) or a movement profile.

Red Seal Rule: Movement joints must be planned in the design and must never be covered with grout. A missing movement joint is a common cause of delamination and cracking.

5. Grout

5.1 Types of Grout

Type	Composition	Joint Width	Use
Sanded cement grout	Cement + sand	6 mm and wider	Floor tile and exterior walls
Unsanded cement grout	Cement without sand	3 mm and narrower	Small-format wall tile
Epoxy grout	Resin + hardener	All widths	Chemical areas, hospitals, countertops
Furan-based grout	Black resin	All widths	Industrial areas

Choice for Walls: For interior walls, unsanded cement grout is common for 2 to 3 mm joints. For 3 to 6 mm joints, use fine sanded grout.

5.2 Grouting Procedure

85.Wait until the thin-set mortar has cured (24 hours minimum).

86.Clean the joints with a brush to remove debris.

87.Lightly dampen the joints (for cement grout) to slow water absorption.

88.Apply grout with a rubber float, working diagonally across the joints.

89.Completely fill the joints, then remove excess with the float.

90.Allow the grout to set (15 to 30 minutes), then clean the surface with a damp sponge.

91.After 24 hours, polish with a dry cloth to remove the cement haze.

5.3 Calculating Grout Quantity

The amount of grout depends on the width and depth of the joints, as well as the tile format.

Formula:

Quantity (kg/m²) = (Joint width (mm) × Joint depth (mm) × 1.8) / (Tile length (mm) + Tile width (mm))

Example: 300 mm × 300 mm tiles, 3 mm wide joints and 8 mm deep.

Quantity = (3 × 8 × 1.8) / (300 + 300) = 43.2 / 600 = 0.072 kg/m².

For 12 m²: 12 × 0.072 = 0.86 kg of grout.

6. Waterproofing and Moisture Protection

6.1 Waterproofing Membranes

Waterproofing membranes are mandatory in wet areas (showers, bathtubs, exterior walls). They prevent water from penetrating the substrate and causing structural damage or mold.

Membrane Type	Application	Advantages	Disadvantages
Liquid (e.g., RedGard)	Roller or brush	Conforms to complex shapes, no seams	Requires 2 coats, drying time
Sheet (e.g., Kerdi, Schluter)	Bonded with thin-set mortar	Immediate waterproofing, uniform thickness	Higher cost, seams to seal
Composite panel (e.g., Wedi, GoBoard)	Screws + sealant	Integrated insulation, fast installation	High cost, requires specific accessories

Installation Requirements:

The membrane must extend at least 1.8 m above the shower floor.

All joints and penetrations (faucets, showerheads) must be sealed with a compatible sealant.

The membrane must be installed before tile installation.

6.2 Slope and Drainage

In a shower, the floor must have a slope of 1.5% to 2% (approximately 15 to 20 mm per meter) toward the drain. Walls must be perfectly vertical (plumb), but the floor must be sloped to prevent water accumulation.

Exam Trap: Insufficient slope (< 1%) causes water pooling and long-term damage. Excessive slope (> 2%) makes walking uncomfortable and can cause tiles to slip.

7. Applicable Standards and Codes

7.1 Canadian Standards

The following standards are cited on the Red Seal exam:

Standard	Title	Application
CSA A23.1	Concrete: Constituents and execution of work	Concrete substrates, mortars
CSA A82	Ceramic tiles	Tile classification
ANSI A118.1	Specifications for thin-set mortars	Thin-set mortars and adhesives
ANSI A118.4	Specifications for grouts	Cement and epoxy grouts
National Building Code (NBC)	Structural and safety requirements	Wall design, loads
Canadian Electrical Code, Part I	Electrical installations	Lighting, receptacles in wet areas

Rule 8-200 of the Canadian Electrical Code, Part I: In bathrooms, receptacles must be protected by a ground fault circuit interrupter (GFCI) and located at least 1 m from the bathtub or shower. The tile setter must coordinate the location of electrical boxes with the electrician.

7.2 NBC Requirements for Walls

Shower walls must be waterproof to a minimum height of 1.8 m.

Finish materials must be water-resistant and easy to clean.

Joints between walls and floor must be watertight.

8. Calculations and Measurements

8.1 Calculating Wall Area

Formula: Area = Perimeter × Height − Area of openings

Example: A bathroom measuring 2.4 m × 3.0 m, wall height of 2.4 m, with a door of 0.9 m × 2.0 m and a window of 0.6 m × 0.9 m.

126.Perimeter = 2 × (2.4 + 3.0) = 10.8 m

127.Gross area = 10.8 × 2.4 = 25.92 m²

128.Door area = 0.9 × 2.0 = 1.8 m²

129.Window area = 0.6 × 0.9 = 0.54 m²

130.Net area = 25.92 − 1.8 − 0.54 = 23.58 m²

Add 10% for cuts and waste: 23.58 × 1.10 = 25.94 m² of tile to order.

8.2 Number of Tiles

Formula: Number of tiles = Net area / Area of one tile

Example: 300 mm × 300 mm tiles (0.09 m²).

Number = 23.58 / 0.09 = 262 tiles.

Add 10%: 262 × 1.10 = 288 tiles.

8.3 Calculating Thin-Set Mortar Quantity

Formula: Quantity (kg) = Area (m²) × Consumption (kg/m²) × 1.10 (waste)

Example: Area of 23.58 m², consumption of 4.5 kg/m².

Quantity = 23.58 × 4.5 × 1.10 = 116.7 kg.

9. Pitfalls to Avoid

143.Setting tile on an unprepared substrate: A dusty or greasy wall reduces adhesion by more than 50%. Always clean the surface before starting.

144.Ignoring mortar open time: Setting a tile on mortar that has skinned over is a critical error. The tile will delaminate over time.

145.Using an inappropriate trowel: A trowel too small for the tile format does not provide sufficient coverage. Check coverage by lifting a tile after placement.

146.Forgetting movement joints: Movement joints at changes in plane and every 6 to 8 m are mandatory. Their absence causes cracking and delamination.

147.Not waterproofing wet areas: A waterproofing membrane is mandatory in showers and bathtubs. Using standard gypsum board without a membrane is a major failure.

148.Calculating area without deducting openings: Not subtracting doors and windows results in over-ordering materials and waste.

149.Installing diagonally without planning for cuts: Diagonal installation increases waste by 15 to 20%. Always plan for 15% waste for this type of installation.

150.Using unsanded grout for wide joints: Unsanded grout cracks in joints wider than 3 mm. Use sanded grout for wider joints.

151.Not checking wall plumb: A wall that is not vertical causes tile alignment problems and uneven joints. Check with a 2 m level before starting.

152.Setting large-format tile with a trowel that is too small: Tiles larger than 300 mm require a 12 mm trowel or larger and high-performance mortar.

10. Summary

Substrate preparation: The surface must be clean, dry, and free of contaminants. Use cement board in wet areas.

Thin-set mortars: Choose the type and trowel based on tile format. Respect open time and minimum coverage (80% interior, 95% wet areas).

Movement joints: Mandatory at changes in plane and every 6 to 8 m. Never cover them with grout.

Waterproofing: Wet areas require a liquid or sheet membrane, extending to a minimum of 1.8 m.

Grout: Choose the type based on joint width. Epoxy grout is recommended for areas with high chemical exposure.

Calculations: Net area = perimeter × height − openings. Add 10% waste (15% for diagonal installation).

Standards: Refer to the NBC, CSA A23.1 and A82 standards, and ANSI A118.1 and A118.4. Respect the electrical clearances of the Canadian Electrical Code, Part I (Rule 8-200).

11. Self-Assessment Questions

164.What is the minimum thin-set mortar coverage for a shower wall?

Answer: 95% of the tile surface.

166.What is the recommended slope for a shower floor?

Answer: 1.5% to 2% (15 to 20 mm per meter).

168.What is the minimum waterproofing height in a shower?

Answer: 1.8 m above the floor.

170.What type of trowel is required for 600 mm tiles?

Answer: 12 mm (square-notch) trowel or larger.

172.What is the maximum distance between movement joints on a wall?

Answer: 6 to 8 linear meters.

174.What is the typical open time of a thin-set mortar?

Answer: 15 to 30 minutes depending on type and temperature.

176.Which standard governs thin-set mortars?

Answer: ANSI A118.1.

178.What is the recommended waste factor for diagonal installation?

Answer: 15 to 20%.

180.What is the minimum width of a movement joint?

Answer: 6 mm.

182.What type of grout is recommended for 2 mm joints?

Answer: Unsanded cement grout.

12. References

National Building Code of Canada (NBC), current edition.

CSA A23.1, Concrete: Constituents and execution of work.

CSA A82, Ceramic tiles.

ANSI A118.1, Specifications for thin-set mortars.

ANSI A118.4, Specifications for grouts.

Canadian Electrical Code, Part I, Rule 8-200.

Technical guides from waterproofing membrane manufacturers (Schluter, Laticrete, Mapei).

This chapter prepares you for the theoretical questions and calculations on the Red Seal exam. Review the standards and formulas, and practice area and material calculations until they become automatic.

Wall Tile Installation