Course outline
Module 1
Module 1: Introduction to Plastering Tools and Materials
Introduction to Plastering Tools and Materials
Knowledge check
Q1. Which tool is primarily used to spread and smooth plaster onto a wall surface?
- A. Spirit level
- B. Steel trowel ✓
- C. Plumb bob
- D. Chalk line
Why: A steel trowel is the main hand tool for applying, spreading, and smoothing plaster. Spirit levels and plumb bobs check alignment, and chalk lines mark straight guidelines, so they are not used for spreading plaster.
Q2. What is the purpose of a hawk in plastering?
- A. To cut plasterboard to size
- B. To hold a small amount of plaster while working ✓
- C. To measure wall thickness
- D. To mix plaster with water
Why: A hawk is a flat square board with a handle underneath. It holds a manageable quantity of plaster so the plasterer can transfer it to the trowel without repeatedly returning to the mixing bucket.
Q3. Which material is most commonly used as a base coat for plastering interior walls?
- A. Gypsum-based plaster ✓
- B. Pure cement mortar only
- C. Epoxy resin
- D. Wood glue
Why: Gypsum-based plasters are widely used for interior walls because they set quickly, are easy to work with, and produce a smooth finish. Epoxy resin and wood glue are not plaster materials, and pure cement mortar is more typical for exterior or heavy-duty work.
Q4. What tool is used to create a straight, flat surface by drawing a straight edge across wet plaster?
- A. Float ✓
- B. Hammer
- C. Plumb line
- D. Utility knife
Why: A float, often a long wooden or plastic tool, is drawn across the plaster to level and flatten it. A hammer, plumb line, and utility knife do not serve this function.
Q5. Why should plastering tools be cleaned promptly after use?
- A. To make them shine for display
- B. Because dried plaster becomes hard to remove and can damage tools ✓
- C. To change the plaster's color
- D. Because plaster tools rust only when left dry
Why: Plaster hardens quickly once it dries, making it difficult to remove from tools and potentially ruining edges and surfaces. Prompt cleaning keeps tools in good condition and ready for the next job.
Module 2
Module 2: Surface Preparation and Priming
Surface Preparation and Priming
Knowledge check
Q1. What is the main purpose of cleaning a substrate thoroughly before applying plaster?
- A. To change the colour of the wall
- B. To remove dust, grease and loose material so the plaster can bond properly ✓
- C. To make the wall warmer to the touch
- D. To reduce the total thickness of the plaster coat
Why: Dust, grease, release agents and loose particles prevent plaster from adhering to the substrate, which can cause delamination and cracking later.
Q2. Which of the following is a common purpose of applying a bonding agent or PVA primer to a dense, smooth substrate such as concrete?
- A. To make the plaster harden faster in cold weather
- B. To provide a key and improve adhesion between the substrate and the plaster ✓
- C. To waterproof the wall completely
- D. To remove efflorescence from brickwork
Why: Smooth, dense surfaces offer little mechanical grip, so bonding agents help the plaster adhere by improving surface texture and wetting behaviour.
Q3. Why should a new plasterboard surface be primed before skimming with plaster?
- A. To stop the board from absorbing too much water from the plaster, which can cause uneven drying and visible marks ✓
- B. To make the board stronger structurally
- C. To prevent the board from being painted later
- D. To remove the paper facing from the board
Why: Plasterboard paper is highly absorbent; without sealing, it draws water out of the skim too quickly, causing poor bonding, cracking and blotchy finish.
Q4. What is a sign that a substrate is too powdery or friable to plaster directly?
- A. It feels cool to the touch
- B. Dust or powder comes off when rubbed with a hand or brush and the surface crumbles easily ✓
- C. It has a smooth, glossy painted finish
- D. It is a dark colour
Why: Friable surfaces lack cohesion; a consolidating primer should be applied to strengthen them so the plaster has a stable base to bond to.
Q5. Before priming a surface, why is it important to check the moisture content of the substrate?
- A. Damp surfaces can prevent primers from adhering and may cause the new plaster to fail or blister ✓
- B. Moisture makes primer change colour
- C. Damp walls are always easier to plaster
- D. Moisture content has no effect on plaster adhesion
Why: Excess moisture interferes with primer bonding and can trap water behind the plaster, leading to bond failure, staining and blistering.
Module 3
Module 3: Mixing Plaster to the Right Consistency
Mixing Plaster to the Right Consistency
Knowledge check
Q1. What is the main reason plaster should be mixed to a consistent, lump-free texture?
- A. To make the plaster cheaper to produce
- B. To ensure even adhesion, smooth application, and a uniform finish on the wall
- C. To speed up the drying time of the plaster
- D. To increase the color intensity of the finished surface
Q2. Which tool is most commonly used to mix plaster to a smooth consistency?
- A. A trowel
- B. A paint roller
- C. A mechanical paddle mixer attached to a drill
- D. A spirit level
Q3. What is a common sign that plaster has too much water in the mix?
- A. It feels stiff and crumbles when lifted on the trowel
- B. It is runny, slides off the trowel, and sags on the wall
- C. It forms lumps that will not break down
- D. It turns a bright blue color
Q4. What happens if plaster is mixed with too little water?
- A. It becomes too runny and drips off the wall
- B. It becomes stiff and hard to spread, and may cause cracking or poor bonding
- C. It sets instantly and cannot be used at all
- D. It produces a glossy, mirror-like finish
Q5. Why should you add powder to water rather than water to powder when mixing plaster?
- A. Adding water to powder causes the powder to clump and makes it harder to achieve an even mix, while adding powder to water helps it disperse evenly
- B. Water added to powder makes the plaster change color
- C. Powder added to water is required by law in all countries
- D. There is no difference; either method produces identical results
Module 4
Module 4: Applying the First Coat
Applying the First Coat
Knowledge check
Q1. What is the main purpose of the first coat, known as the scratch coat, in a plaster application?
- A. To create a smooth, decorative finish on the wall
- B. To provide a mechanical key and base for subsequent coats to adhere to ✓
- C. To fully level out the surface so no further coats are needed
- D. To seal the substrate against all moisture penetration
Why: The scratch coat is applied to bond firmly to the substrate and is scored with horizontal grooves so that the following coats have a mechanical key to grip onto, which is essential for adhesion and preventing cracking or delamination.
Q2. Why is the scratch coat typically scored with horizontal lines before it sets?
- A. To make the wall look more attractive before painting
- B. To remove excess water from the mix
- C. To improve the mechanical key so the next coat bonds properly ✓
- D. To help the plaster dry faster by increasing surface area
Why: Scoring creates grooves and roughened texture that give the next coat something to grip, improving adhesion between layers. The lines are usually made horizontally so the key is consistent across the wall.
Q3. Before applying the first coat to a brick or block wall, what should the surface be prepared with?
- A. A coat of gloss paint to repel the plaster
- B. Dampening with water and removing dust, dirt, and loose material ✓
- C. A layer of sand spread evenly over the surface
- D. A thick application of PVA undiluted straight from the bottle
Why: Dampening the substrate reduces its suction so it does not draw water out of the plaster too quickly, and removing dust and loose particles ensures a clean bond. Dry, dusty surfaces lead to weak adhesion and poor performance.
Q4. What is the typical recommended thickness for a scratch coat applied to a standard wall?
- A. Less than 1 mm, applied as a thin wash
- B. About 1 cm to 1.5 cm ✓
- C. Around 5 cm to ensure full coverage
- D. Exactly 20 mm regardless of conditions
Why: A scratch coat is usually applied at around 1 to 1.5 cm thick to build up a sound base. Applying it too thinly risks poor coverage, while excessively thick single coats can crack or take too long to dry.
Q5. Why should the first coat be allowed to partially set before the scoring is done?
- A. Because the plaster must be fully cured before any work continues
- B. So the surface is firm enough to hold the grooves without collapsing or tearing ✓
- C. To allow the plaster to change colour, indicating it is ready
- D. Because scoring is only possible on fully dry plaster with a hard tool
Why: Scoring is done once the coat has stiffened but is still workable, so the grooves hold their shape. Scoring too early can smear or collapse the material, while waiting until it is fully hard makes the key difficult to create and weakens the bond.
Module 5
Module 5: Levelling and Smoothing Techniques
Levelling and Smoothing Techniques
Knowledge check
Q1. What is the main purpose of using a feather edge when plastering a wall?
- A. To speed up the drying time of the plaster
- B. To create a smooth, seamless transition between old and new plaster ✓
- C. To add decorative texture to the surface
- D. To strengthen the bond between plaster and brick
Why: A feather edge is a thin, tapered edge of plaster that blends smoothly into the surrounding surface, so the repair is not visible once finished.
Q2. Which tool is most commonly used to level and smooth wet plaster on a large wall area?
- A. A plasterer's trowel ✓
- B. A hacksaw
- C. A plumb bob
- D. A spirit level only
Why: A plasterer's trowel is used to spread, level and smooth wet plaster. A spirit level checks levelness but does not apply or smooth the plaster.
Q3. What is a 'screed' in plastering terms?
- A. A type of plaster mixed with sand
- B. A straight guide, usually a timber or aluminium rail, used to level plaster between grounds ✓
- C. A brush used to apply a final finish coat
- D. A chemical additive that speeds up setting
Why: A screed is a straight edge drawn across guides (grounds) to bring the wet plaster to a flat, level surface before finishing.
Q4. Why should a plasterer work the surface with a wood float before the final steel trowel finish?
- A. To remove all moisture from the plaster
- B. To close the surface and bring up fine material for a uniform texture ✓
- C. To apply colour to the wall
- D. To prevent the plaster from ever cracking
Why: Floating compacts the coat, removes minor high spots and hollows, and brings fines to the surface so that the steel trowel can produce a smooth finish.
Q5. What is the most likely result of troweling plaster too early, before it has begun to stiffen?
- A. A harder, more durable surface
- B. Surface dragging, uneven texture and loss of the finish ✓
- C. Faster curing of the plaster
- D. Improved adhesion to the substrate
Why: Troweling too early drags the wet material, causing ridges, uneven texture and a poor finish. Waiting until the plaster stiffens gives a clean, smooth result.
Module 6
Module 6: Finishing Coats and Texturing
Finishing Coats and Texturing
Knowledge check
Q1. What is the primary purpose of a finishing coat in plastering?
- A. To add structural strength to the wall
- B. To provide a smooth, even surface ready for decoration ✓
- C. To waterproof the substrate completely
- D. To fill large cracks deeper than 20mm
Why: The finishing coat creates a smooth, uniform surface that can be painted or decorated, while structural strength comes from the base coats.
Q2. Which material is most commonly used for a fine finishing coat on interior walls?
- A. Coarse sharp sand and cement
- B. Gypsum-based finish plaster ✓
- C. Bitumen emulsion
- D. Concrete mix with gravel
Why: Gypsum-based finish plasters are fine, workable, and set to a smooth surface ideal for interior finishing.
Q3. What is the typical thickness range for a finishing coat applied over a base coat?
- A. 1 to 3 mm ✓
- B. 10 to 15 mm
- C. 25 to 30 mm
- D. 40 to 50 mm
Why: Finishing coats are usually applied very thinly, around 1 to 3 mm, to avoid cracking and to achieve a smooth surface.
Q4. Why should the base coat be scratched or keyed before applying a finishing coat?
- A. To remove all moisture from the wall
- B. To improve adhesion between the layers ✓
- C. To make the wall visibly rougher for paint
- D. To speed up the drying time
Why: Scoring or keying the base coat gives the finishing coat a mechanical grip, improving bond and reducing the risk of delamination.
Q5. Which texturing technique involves dragging a loaded brush or sponge across wet plaster to create a patterned finish?
- A. Stippling ✓
- B. Sanding
- C. Troweling flat
- D. Priming
Why: Stippling uses a brush, sponge, or stipple tool pressed or dabbed onto wet plaster to create a textured pattern; sanding and priming are not texturing techniques.
Module 7
Module 7: Cleaning Up and Common Mistakes
Cleaning Up and Common Mistakes
Knowledge check
Q1. What is the best time to clean your plastering tools after finishing a session?
- A. After the plaster has fully dried on them
- B. Immediately after use, before plaster hardens ✓
- C. Only at the end of the week
- D. Only when the tools look visibly dirty
Why: Plaster begins to set within minutes and becomes very difficult to remove once hardened. Cleaning tools right after use with water keeps them in good condition and prevents build-up.
Q2. Which tool is most useful for removing small amounts of dried plaster from a trowel's edge?
- A. A hammer
- B. A wire brush or scraper ✓
- C. Sandpaper of very coarse grit
- D. Hot water poured directly on the blade
Why: A wire brush or putty knife scraper can lift dried plaster without damaging the steel surface. Hammers can dent or bend tools, and hot water does not reliably soften set plaster.
Q3. A common beginner mistake when applying plaster is:
- A. Dampening the wall before application
- B. Mixing only the amount you can use within the working time
- C. Applying plaster too thickly in a single coat ✓
- D. Keeping a clean bucket for mixing
Why: Applying plaster too thickly in one coat often leads to cracking, slow drying, and poor adhesion. Multiple thinner coats produce a stronger, more even finish.
Q4. What should you do with leftover wet plaster that has started to set in your mixing bucket?
- A. Pour it down the drain to dispose of it
- B. Let it harden fully and throw it in the regular bin ✓
- C. Add more water and remix it to use it again
- D. Leave it in the bucket for the next job
Why: Plaster that has started to set should not be re-wet and reused, as its strength is compromised. Letting it harden and disposing of it as solid waste protects drains from blockages and follows safe disposal practice.
Q5. Which of the following is a sign that your plaster was applied over a surface that was not prepared properly?
- A. A smooth, even finish after drying
- B. Plaster peeling or bubbling away from the wall ✓
- C. Consistent color across the whole wall
- D. Minimal dust during sanding
Why: Peeling or bubbling usually means the plaster did not bond well, often because the surface was dusty, greasy, too smooth, or not dampened. Proper preparation is essential for good adhesion.