Wallcovering Installation and Repair
Module Introduction
This chapter covers all the skills required for the Red Seal exam in painting and decorating related to wallcoverings. You will find the fundamental principles, calculation methods, installation procedures, repair techniques, and applicable Canadian standards. Mastering this content is essential, as wallcovering questions typically represent 8 to 12% of the exam.
Definitions and Essential Terminology
Wallcovering: material applied to an interior surface to protect and decorate it. There are two main categories: roll wallcoverings (wallpaper, vinyl, fabric) and panel wallcoverings (wainscoting, wall panels).
Butt joint: installation technique where strips are placed side by side without overlapping. This is the standard method for pre-pasted wallcoverings and vinyls.
Lap joint: technique where one strip slightly overlaps the previous one. Used for certain papers requiring a match, then cut through with a utility knife to create a double cut joint.
Straight match: the pattern repeats horizontally at the same level on all strips.
Drop match: the pattern repeats diagonally; the next strip must be offset by half a repeat.
Pattern repeat: vertical distance between two identical occurrences of the pattern. Expressed in centimetres or inches.
Pasting: application of adhesive to the substrate (wall pasting) or to the wallcovering (strip pasting). The method depends on the type of wallcovering.
Pre-pasted: wallcovering whose backing is already coated with dry adhesive; it must be activated by immersing it in water.
Strippability: ability of a wallcovering to be easily removed. There are three types: peelable, strippable (removes leaving a residue), and non-removable.
Estimating: calculation of the number of rolls needed to cover a room.
Wallcovering Classification
By Substrate
| Type | Characteristics | Typical Use |
|---|
| Paper | Lightweight, not moisture-resistant | Bedrooms, living rooms |
| Vinyl on paper | Moisture-resistant, washable | Kitchens, bathrooms |
| Vinyl on fabric (expanded vinyl) | Very durable, hides imperfections | Corridors, commercial areas |
| Fabric (canvas, jute) | Textured appearance, difficult to install | Accent walls, hospitality |
| Non-woven (non-woven fabric) | Paste-the-wall installation, dry-strippable | High-end residential |
| Fibreglass | Very durable, fire-resistant | Institutional buildings |
By Surface Treatment
Laminated vinyl: layer of vinyl applied to a paper backing. Resists washing.
Expanded vinyl: vinyl with embossed relief, requires special adhesive to prevent bubbles.
Embossed paper: relief created by pressure, often used to hide surface defects.
Flocked: velvety surface, very delicate, cannot be washed.
By Installation Method
Paste-the-wall: for non-woven and some heavy vinyls. Adhesive is applied with a roller directly to the wall.
Paste-the-strip: for standard papers and vinyls. Adhesive is applied to the backing of the wallcovering.
Pre-pasted: activated by immersion in a water tray.
Self-adhesive: remove the protective film, install directly.
Calculations and Estimating
Calculating the Number of Rolls
Basic formula for a rectangular room:
Room perimeter = 2 × (length + width)
Number of full strips = Perimeter ÷ Strip width (round up to the nearest whole number)
Strip height = Wall height + 10 cm (trimming allowance)
Usable length per roll = Roll length ÷ Strip height (round down to the nearest whole number)
Number of rolls = Number of full strips ÷ Number of strips per roll (round up to the nearest whole number)
Worked Example
Room measuring 4.5 m × 3.6 m, ceiling height of 2.4 m. Rolls are 10 m × 0.53 m.
Perimeter = 2 × (4.5 + 3.6) = 16.2 m
Number of strips = 16.2 ÷ 0.53 = 30.6 → 31 strips
Strip height = 2.4 + 0.10 = 2.5 m
Strips per roll = 10 ÷ 2.5 = 4 strips
Rolls = 31 ÷ 4 = 7.75 → 8 rolls
Adjustments for Pattern Matches
If the wallcovering has a drop match with a 0.64 m repeat:
Adjusted strip height = 2.5 m rounded up to the next multiple of 0.64 m → 2.56 m
Strips per roll = 10 ÷ 2.56 = 3.9 → 3 strips
Rolls = 31 ÷ 3 = 10.33 → 11 rolls
Rule of thumb: add 10% waste for windows, doors, and cuts. For complex pattern matches, add 15 to 20%.
Calculating Adhesive
Adhesive consumption depends on the type of wallcovering and the porosity of the substrate. On average:
Lightweight paper: 150 to 200 g/m²
Standard vinyl: 200 to 250 g/m²
Heavy vinyl or non-woven: 250 to 300 g/m²
Fabric: 300 to 400 g/m²
Surface to paste = Perimeter × Height − (Area of openings × 0.5)
Openings are only subtracted at 50% because offcuts around frames still require adhesive.
Substrate Preparation
Fundamental Requirements
The substrate must be:
64.Clean: free of dust, grease, wax, or residue.
65.Dry: relative wall moisture below 15% (measured with a moisture meter).
66.Smooth: defects greater than 1 mm must be filled and sanded.
67.Stable: no active cracks or blistering.
68.Uniformly absorbent: apply a sizing primer on new or highly porous walls.
Treatment of Specific Substrates
| Substrate | Required Treatment |
|---|
| New plaster | Sanding, dust removal, sizing primer |
| Old plaster | Washing, rinsing, crack filling |
| Drywall (gypsum board) | Sanded joints, dust removal, sizing primer |
| Concrete | Cleaning, patching, sizing primer |
| Wood | Sanding, application of a pore sealer |
| Existing paint | Washing, rinsing, light sanding if glossy |
| Old wallcovering | Adhesion assessment, removal if necessary |
Adhesion Test for Old Wallcovering
Apply adhesive tape to the old wallcovering and pull it off with a quick motion. If pieces come off, the wallcovering must be removed. A second test involves making a cross-cut with a utility knife and attempting to lift the corners.
Removing Old Wallcoverings
Strippable wallcovering: pull gently by hand or with a putty knife.
Non-removable wallcovering: use a steam stripper or a hot water solution with a wetting agent.
Perforation: for vinyls on paper, puncture the surface with a scoring tool to allow water to penetrate.
Chemical products: apply a commercial stripper, let it sit for 15 to 20 minutes, then scrape.
Caution: never use chemical strippers on gypsum board without protection — the liquid can damage the paper facing.
Tools and Equipment
Measuring and Marking Tools
Laser level or 1.2 m spirit level
Plumb bob: for marking the reference vertical line
Tape measure of at least 8 m
Chalk line
Carpenter's square: for checking the squareness of corners
Cutting Tools
Utility knife with snap-off blades: new blade for each installation
Wallpaper shears: for long cuts
Metal straightedge of 1 m
Tin snips: for heavy vinyls
Installation Tools
Smoothing brush (25 to 30 cm wide): for flattening the wallcovering
Seam roller (5 cm wide): for pressing down edges
Water tray: for pre-pasted wallcoverings
Pasting table: work surface for applying adhesive
Paste brush or long-nap roller
Clean sponge: for wiping off excess adhesive
Putty knife: for corners and baseboards
Safety Equipment
Safety glasses
Nitrile gloves
Dust mask (N95) when sanding
Stable ladder compliant with provincial standards
Installation Procedures
Step 1: Batch Verification
Verify that all rolls have the same batch number. Different batches may have colour variations. If necessary, mix rolls by alternating strips.
Step 2: Marking the Reference Vertical Line
110.Choose a starting point: a corner, door, or window.
111.Measure the strip width minus 1 cm from the corner.
112.Mark a vertical line using a plumb bob or laser level.
113.Mark the line with a pencil — never a pen (ink can bleed through the wallcovering).
Golden rule: check the squareness of walls. Corners are never perfectly square; the reference vertical line must be marked at every corner.
Step 3: Cutting Strips
Cut strips to the calculated height plus 5 cm allowance at the top and bottom.
For patterned wallcoverings, cut the first strip, then align the pattern of the second before cutting.
Number each strip on the back with a pencil to avoid ordering errors.
Step 4: Pasting
For paste-the-strip:
121.Place the strip on the pasting table, backing side up.
122.Apply adhesive to the centre, then spread toward the edges in crisscross motions.
123.Fold the strip accordion-style (book folding): fold both ends toward the centre, without creasing the folds.
124.Allow to soak for 5 to 10 minutes (soaking time) depending on the type of wallcovering.
For paste-the-wall (non-woven):
126.Apply adhesive with a roller to the wall, slightly wider than the strip.
127.Install the strip directly onto the pasted wall.
128.No soaking time required.
Step 5: Hanging the Strip
130.Position the strip against the ceiling with a slight overlap (2 to 3 cm).
131.Align the edge with the reference vertical line.
132.Smooth from the centre toward the edges with the smoothing brush, pushing out air bubbles.
133.Trim the excess at the top and bottom with a utility knife, following the ceiling and baseboard lines.
134.Wipe off any excess adhesive immediately with a damp sponge.
Step 6: Hanging Subsequent Strips
Align the edge of the new strip with the edge of the previous one (butt joint).
For drop matches, verify pattern alignment before smoothing.
Use the seam roller to press down edges after installation.
Step 7: Corners and Angles
Inside corners:
141.Measure the distance between the edge of the last strip and the corner (at the ceiling, centre, and baseboard).
142.Take the largest measurement, add 1 cm.
143.Cut the strip to this width.
144.Install the strip, wrapping the 1 cm excess around the corner.
145.Mark a new vertical line on the adjacent wall at the width of the remaining strip.
Outside corners:
147.Measure the distance from the edge to the corner, add 3 cm.
148.Install the strip, wrapping the excess around the corner.
149.Mark the crease with a putty knife.
150.Cut along the crease with a utility knife.
151.Install the next strip, aligning the edge with the crease.
Step 8: Around Openings
Install the full strip over the opening.
Make a diagonal cut from the centre of the opening toward the corners.
Smooth the flaps against the frame.
Trim the excess with a utility knife following the frame.
For electrical outlets: turn off the power at the panel, remove the cover plate, install the strip, make an X-cut, trim, and replace the plate.
Pattern Matching and Alignment
Types of Pattern Matches
| Type | Description | Estimated Waste |
|---|
| No match (random pattern) | No alignment required | 0 to 5% |
| Straight match | Pattern aligned horizontally | 10 to 15% |
| Drop match | Pattern offset by half a repeat | 15 to 25% |
| Reverse match | Every other strip is reversed | 20 to 30% |
Drop Match Procedure
163.Cut the first strip.
164.Unroll the second strip next to the first.
165.Slide vertically until the pattern aligns.
166.Cut to the desired length.
167.Number strips in pairs (1a, 1b, 2a, 2b) to avoid errors.
Exam tip: for a drop match with a 0.32 m repeat and a 2.5 m height, the offset between even and odd strips is 0.16 m (half the repeat).
Wallcovering Repair
Repairing Tears and Bubbles
Bubble (air pocket):
173.Make an X-cut in the bubble with a utility knife.
174.Carefully lift the flaps.
175.Inject adhesive using a syringe.
176.Smooth and roll the edges.
177.Wipe off excess adhesive.
Tear:
179.If the tear is less than 5 cm: apply adhesive under the edges, press, and roll.
180.If the tear is larger: replace the section of wallcovering.
Replacing a Section of Wallcovering
182.Mark a rectangle around the damaged area with a straightedge and utility knife.
183.Remove the damaged section.
184.Use this section as a template to cut the new piece.
185.Ensure the pattern of the new piece aligns perfectly.
186.Paste the new piece and install it.
187.Roll the edges with the seam roller.
Invisible Seam
For an invisible seam, cut the new piece larger than the opening, then cut through both layers together (double-cut technique). This guarantees a perfectly fitted joint.
Applicable Standards and Codes
National Building Code of Canada (NBC)
The NBC does not contain specific rules for wallcovering installation, but it does impose requirements on interior surfaces:
Article 9.5.1.1: interior surfaces must be durable, easy to clean, and not present health hazards.
Article 9.29.4.1: roll wallcoverings must be installed on a clean and dry substrate.
Canadian Electrical Code, Part I
Rule 8-200: electrical outlets and switches must be accessible. Wallcovering must not obstruct access to electrical boxes. Cover plates must be removed before installation and replaced after.
CSA Standards
CSA A82: standard for gypsum plasterboard — the substrate must be compliant before wallcovering installation.
CSA O118: standard for plywood — applicable if the wallcovering is installed on a wood substrate.
Occupational Health and Safety Act
Adhesive products must have a Safety Data Sheet (SDS) accessible on the job site.
Ventilation must be adequate when applying adhesives containing solvents.
Ladders must comply with CSA standards and be used according to best practices.
Quality Control and Inspection
Post-Installation Checks
| Check Point | Acceptance Criteria |
|---|
| Seams | Invisible, no gaps or overlaps |
| Bubbles | No visible blisters |
| Pattern alignment | Perfect over the full height |
| Corners | Clean, no wrinkles or tears |
| Edges | Adhered, no lifting |
| Cleanliness | No adhesive residue on the surface |
Common Defects and Causes
| Defect | Probable Cause |
|---|
| Bubbles after drying | Unprimed substrate, adhesive too diluted, insufficient smoothing |
| Seams opening up | Wallcovering shrinkage, unsuitable adhesive, overly absorbent substrate |
| Visible overlap | Imprecise cutting, strip not perpendicular |
| Misaligned pattern | Incorrect repeat calculation, mixed strips |
| Discolouration | Sun exposure, different batch |
| Mould | Excessive humidity, untreated substrate |
Pitfalls to Avoid
213.Not checking the batch number: colour variations between batches make seams visible. Always check before starting.
214.Skipping the sizing primer: on a porous substrate, adhesive is absorbed too quickly and the wallcovering does not adhere properly. Primer evens out absorption.
215.Marking the vertical line with a short spirit level: levels under 1 m amplify errors. Use a plumb bob or laser level.
216.Confusing straight match and drop match: the roll calculation changes significantly. A drop match can require 30% more wallcovering.
217.Forgetting the soaking time: a pre-pasted wallcovering installed too soon will not adhere; installed too late, the adhesive dries and the wallcovering deforms.
218.Smoothing too vigorously: on expanded vinyls, excessive pressure crushes the relief and creates permanent marks.
219.Neglecting to cut the power: when installing around outlets, always turn off the circuit at the panel. Water and adhesive are conductors.
220.Using a dull utility knife: a worn blade tears the wallcovering instead of cutting it. Change the blade frequently.
221.Underestimating substrate preparation: 80% of installation defects come from a poorly prepared substrate. Never skip this step.
222.Not accounting for temperature: adhesive should not be applied below 10 °C or above 30 °C. Ideal relative humidity is 40 to 60%.
Summary
Wallcoverings are classified by substrate (paper, vinyl, fabric, non-woven) and by installation method (paste-the-wall, paste-the-strip, pre-pasted, self-adhesive).
Roll calculations must account for perimeter, height, strip width, pattern repeat, and waste (10 to 20%).
Substrate preparation is the most critical step: the substrate must be clean, dry, smooth, stable, and uniformly absorbent.
The reference vertical line must be marked with a plumb bob or laser level, never a short level.
Inside corners are installed with a 1 cm return; outside corners with a 3 cm return.
Drop matches require a half-repeat offset between even and odd strips.
Common repairs include adhesive injection for bubbles and section replacement using the double-cut technique.
Applicable standards include the NBC (Articles 9.5.1.1 and 9.29.4.1) and the Canadian Electrical Code, Part I (Rule 8-200).
Quality control must verify seams, bubbles, alignment, corners, and cleanliness.
Self-Assessment Questions
236.A room measures 5.2 m × 4.1 m with a ceiling height of 2.7 m. Rolls are 10 m × 0.53 m with a 0.64 m drop match. How many rolls are needed?
237.What is the difference between a strippable wallcovering and a peelable wallcovering?
238.Why must a reference vertical line be marked at every inside corner?
239.What is the recommended soaking time for a standard pre-pasted wallcovering?
240.What are the three adhesion tests for evaluating an old wallcovering?
241.What is the correct procedure for installing wallcovering around an electrical outlet?
242.A seam opens after drying. What are the three probable causes and how do you correct them?
This chapter covers competencies C-10 to C-18 of the Red Seal qualification profile for the painter-decorator trade. Make sure you master estimating calculations and installation procedures before moving on to the following chapters.
