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CAP Carreleur Mosaïste study materials
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CAP Carreleur Mosaïste practice questions

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Question 1Tiling substrates, adhesive systems, water management and movement

What does the additional classification 'S1' signify when an adhesive mortar is designated as 'C2S1'?

  1. The adhesive is fast-setting within 1 hour
  2. The adhesive is deformable, exhibiting a transverse deformation between 2.5 mm and 5.0 mm under EN 12002 testing Correct answer.
  3. The adhesive contains sand with a grain size smaller than 0.1 mm
  4. The adhesive is waterproof and can replace a roofing membrane

Explanation

Under EN 12004 and test standard EN 12002, the 'S' designation denotes transverse deformability (*déformabilité transversale*). An S1 adhesive (*mortier colle déformable*) flexes between 2.5 mm and 5.0 mm without bond failure, making it essential for heated floors, exterior facades, and large-format tiles.

Question 2Tiling substrates, adhesive systems, water management and movement

A tiler installs large-format porcelain tiles on a 50 m² floor using double buttering (*double encollage*): a U9 notched trowel on the floor (4.5 kg/m²) plus a flat buttering pass on the tile back (2.0 kg/m²), giving a total consumption of 6.5 kg/m². How many 25 kg bags are needed?

  1. 9 bags
  2. 11 bags
  3. 13 bags Correct answer.
  4. 16 bags

Explanation

Total adhesive powder required = 50 m² × 6.5 kg/m² = 325 kg. Number of 25 kg bags = 325 kg / 25 kg/bag = exactly 13 bags.

Question 3Tiling substrates, adhesive systems, water management and movement

Which listed early excessive-washing practice can contribute to weak or discolored cementitious grout, rather than uniquely diagnose every grout defect?

  1. Washing too early with an overly saturated, dripping sponge Correct answer.
  2. Using an abrasive diamond disc
  3. Allowing the grout to cure for 7 days before touching it
  4. Using warm soapy water with vinegar

Explanation

Washing the joints too prematurely with an excessively wet sponge washes out the cement binder and pigments (*creusement des joints*), introduces surplus water that drives soluble salts to the surface (causing white efflorescence / *laitance de ciment*), and weakens the final joint hardness. Cleaning should begin only once the grout has begun to firm up (matte appearance).

Question 4Tiling substrates, adhesive systems, water management and movement

What is the key functional advantage of full-body porcelain stoneware (*grès cérame pleine masse*) compared to glazed porcelain (*grès cérame émaillé*) in heavy commercial traffic areas?

  1. If the surface suffers deep scratches or chipping, the color and composition remain identical throughout the entire tile thickness, making damage nearly invisible Correct answer.
  2. It requires no adhesive or mortar during installation
  3. It weighs 80% less than glazed tiles
  4. It can be cut with an ordinary pair of paper scissors

Explanation

Full-body coloration can make some chips less visually contrasting than damage exposing a differently colored body. It does not make damage invisible, repair a broken tile or establish suitability for every load and chemical exposure. Actual finish and product performance still matter.

Question 5Tiling substrates, adhesive systems, water management and movement

When installing glass mosaics mounted on front-face kraft paper (*mosaïque collée sur papier en face avant*), how are the mosaic sheets placed into the adhesive bed?

  1. The paper side is pressed down directly into the wet adhesive mortar
  2. The bare rear face of the glass tesserae is pressed into the adhesive bed, leaving the kraft paper facing outwards towards the room until moistened and peeled off Correct answer.
  3. The paper is burned off with a blowtorch before laying
  4. The paper is permanently left embedded between the screed and tile

Explanation

Paper-faced mosaics (*collés sur papier sur belle face*) have kraft paper adhered to the decorative front side. The bare glass back is pressed into the adhesive bed. Once the adhesive takes its initial set, the tiler sponges water onto the paper, softening the water-soluble glue, and gently peels the paper off diagonally to reveal the joint lines for alignment and grouting.

Question 6Tiling substrates, adhesive systems, water management and movement

How does a manual score-and-snap tile cutter (*carrelette / coupe-carreaux manuel*) execute a straight cut on a ceramic tile?

  1. A high-speed laser melts through the entire thickness of the ceramic
  2. A tungsten carbide or titanium scoring wheel scores the glazed surface under controlled forward pressure, followed by a mechanical breaker foot that snaps the tile along the score line Correct answer.
  3. A hydraulic reciprocating saw blade cuts through the tile submerged in oil
  4. Two sharp steel blades shear the tile like a guillotine

Explanation

A manual tile cutter (*carrelette*) relies on scoring and snapping: a hard tungsten carbide or titanium scoring wheel (*molette*) is pushed with even pressure along the tile face, scoring the surface tension of the glaze and top biscuit. The breaker wings (*séparateur / pieds de casse*) then apply downward lever pressure on either side of the score, causing a clean tensile fracture along the line.

Question 7Tiling substrates, adhesive systems, water management and movement

What are the primary technical and safety advantages of using an electric wet diamond saw (*scie de table à eau*) over dry cutting with an angle grinder?

  1. Water prevents the diamond blade from overheating and burning its solder matrix, delivers smooth chip-free edges, and suppresses dangerous airborne crystalline silica dust Correct answer.
  2. Water speeds up blade rotation to over 50,000 rpm
  3. It allows cutting through steel beams embedded in tiles
  4. The water chemically softens the ceramic biscuit to the consistency of butter

Explanation

Suitable wet cutting can control blade heat and reduce airborne dust compared with uncontrolled dry cutting under the actual equipment instructions. It does not guarantee chip-free edges or eliminate all exposure and electrical hazards. Use the specified blade, guarding and appropriate complete task controls.

Question 8Tiling substrates, adhesive systems, water management and movement

Why can a specified box-blending plan mix tiles from several appropriate boxes during installation, rather than assume every product mandates exactly3or4boxes?

  1. To harmoniously distribute slight industrial shade nuances (*variations de nuance / bain*) across the room, preventing noticeable color blocks Correct answer.
  2. To empty the cardboard boxes faster to clear walking paths
  3. To verify that all tiles are made of plastic
  4. To mix different tile thicknesses together

Explanation

Ceramic manufacturing involves natural raw clays and kiln temperature gradients that create slight, unavoidable variations in tone and shade (*bain / nuance*) between production batches. Mixing tiles from several boxes simultaneously distributes these nuances evenly across the whole floor, preventing jarring checkerboard patches of dark and light tiles.

Question 9Tiling substrates, adhesive systems, water management and movement

Before opening tile boxes on site, what two critical production codes printed on the box labels must the tiler verify are identical across all cartons?

  1. The barcode and delivery truck license plate
  2. The tone/shade code (*nuance / bain*) and the dimensional caliber code (*calibre*) Correct answer.
  3. The store cashier number and invoice date
  4. The plastic wrapping thickness and glue batch number

Explanation

Shade/tone and dimensional-caliber identifiers answer different consistency questions. Verify the actual product and project requirements, including any intended variation, before mixing batches. A matching code does not independently prove that every tile is dimensionally perfect or suitable for the intended exposure.

Question 10Engineering models, drawings, evidence and project decisions

For a supplied42m²tiling job, the order expressly includes7percentallowance. What area follows before packaging-rounding, rather than a universal allowance?

  1. 42.0 m²
  2. 44.94 m² (rounded up to 45.0 m²) Correct answer.
  3. 49.50 m²
  4. 52.50 m²

Explanation

Total tile area to order = Net room area × (1 + waste percentage). Here: 42.0 m² × 1.07 = 44.94 m². In commercial purchasing, orders are rounded up to the nearest full box or square meter, resulting in an order of at least 45.0 m².

Question 11Engineering models, drawings, evidence and project decisions

Why can the specified diagonal layout need a greater cutting allowance than its compared straight layout, with the actual allowance based on the drawing and reusable offcuts?

  1. Diagonal laying requires 45° cuts along all four perimeter walls, producing triangular offcuts that frequently cannot be reused Correct answer.
  2. Diagonal tiles shrink during installation
  3. Diagonal laying uses smaller tiles by law
  4. Grout absorbs extra tile surface in diagonal patterns

Explanation

In diagonal layouts, every perimeter edge requires a 45° angle cut. Because opposing walls rarely match identical offcut geometry, triangular cut pieces often cannot be reused on the opposite side, increasing cutting waste to typically 10% to 15% (30 m² × 1.12 = 33.6 m² -> order 34 m²).

Question 12Tiling substrates, adhesive systems, water management and movement

What does the official French trade acronym 'SPEC' stand for in under-tile wet area protection?

  1. Système de Protection à l'Eau sous Carrelage Correct answer.
  2. Structure Permanente d'Étanchéité en Ciment
  3. Surface Polie Étanche pour Carrelage
  4. Sous-couche Plastifiée pour Eaux Chaudentes

Explanation

SPEC stands for *Système de Protection à l'Eau sous Carrelage*. Regulated by CSTB Cahier 3578, a SPEC is an under-tile liquid-applied synthetic coating designed to protect moisture-sensitive wall and floor substrates from water splashing in domestic wet rooms.

Question 13Tiling substrates, adhesive systems, water management and movement

What does the official French trade acronym 'SEL' stand for in waterproofing systems?

  1. Système d'Étanchéité Liquide Correct answer.
  2. Sol Élastique Léger
  3. Sable d'Enrobage pour Liant
  4. Siphon d'Évacuation Longitudinale

Explanation

SEL stands for *Système d'Étanchéité Liquide*. Governed by technical approval rules and DTU 43.1, an SEL is a certified liquid-applied continuous membrane (polyurethane, acrylic, or polymer-modified cementitious) that cures into a fully watertight barrier capable of withstanding hydrostatic water pressure.

Question 14Tiling substrates, adhesive systems, water management and movement

How is a secure, leak-proof junction achieved between the waterproofing membrane (SEL) and the shower floor drain (*bonde de sol / caniveau*)?

  1. By relying purely on loose gravel around the drain pipe
  2. By integrating a factory-bonded fleece flange (*collerette d'étanchéité*) or mechanical clamping ring (*platine de serrage*) sandwiching the membrane to the drain body Correct answer.
  3. By stuffing paper towels into the gap and covering with cement grout
  4. By drilling drainage holes directly through the floor slab

Explanation

A compatible specified drain connection and membrane detail establish the intended continuity. Actual product system, components, substrate and verification govern performance; a flange name alone does not guarantee a leak-free installation or authorize mixing incompatible details.

Question 15Tiling substrates, adhesive systems, water management and movement

Thin acoustic underlays under tile (*sous-couches acoustiques minces sous carrelage - SCAM*) are engineered primarily to reduce which category of noise?

  1. Impact sound transmission (*bruits de choc / bruits d'impact*), such as footsteps, moving furniture, and dropped objects Correct answer.
  2. Airborne street traffic noise traveling through open windows
  3. Electromagnetic hum from electrical transformers
  4. Ultrasonic bat vocalizations

Explanation

SCAM systems are resilient acoustic underlays installed directly beneath bonded tiles. Their sole acoustic purpose is to attenuate impact noise (*bruits de choc* / *bruits d'impact*) generated by direct footfalls, high heels, and furniture movement, absorbing vibrational energy before it penetrates the concrete floor slab into the apartment below.

Question 16Tiling substrates, adhesive systems, water management and movement

When installing a thin acoustic underlay (SCAM), what critical installation flaw completely ruins the floor's acoustic performance?

  1. Allowing tiles, adhesive, or hard grout to make direct contact with vertical walls or baseboards, creating an acoustic bridge (*pont phonique*) Correct answer.
  2. Using white tiles instead of dark tiles
  3. Installing tiles in a straight pattern instead of diagonal
  4. Leaving the room well ventilated during application

Explanation

A rigid contact across an intended acoustic separation can create a sound bridge and reduce the system’s performance. The degree depends on the actual construction and frequency conditions; it is not necessarily complete loss of all acoustic benefit. Verify the specified separation and workmanship.

Question 17Tiling substrates, adhesive systems, water management and movement

How are water supply pipe outlets (*sorties de tuyauterie*) in shower walls sealed to ensure watertightness before tiling?

  1. By placing elastic sealing collars (*manchettes d'étanchéité*) with flexible rubber gaskets over the pipes and embedding their fleece rims into the SPEC/SEL membrane Correct answer.
  2. By wrapping the pipes in dry cotton rags
  3. By filling the wall cavity with expanding foam and cutting it flush with a knife
  4. By leaving an open 2 cm gap around the pipe for ventilation

Explanation

The specified compatible collars can connect penetrations to the membrane system under the actual approved detail. Other systems may use different validated arrangements. A collar’s presence alone does not prove continuous watertightness, proper installation or complete acceptance.

Question 18Engineering models, drawings, evidence and project decisions

What is the primary technical and aesthetic objective of 'calepinage' in professional tiling practice?

  1. Calculating tile quantities, establishing reference layout axes, and planning symmetrical tile placement to avoid narrow unsightly cut pieces at perimeter edges Correct answer.
  2. Writing the invoice for the customer before beginning work
  3. Mixing tile adhesive powder in large buckets
  4. Selecting the color of the tiler's work overalls

Explanation

*Le calepinage* is the preparatory design, calculation, and layout process where the tiler plans tile positions on blueprint and substrate. It determines reference axes, establishes aesthetic symmetry relative to doors, windows, and focal points, and ensures perimeter cut tiles (*rives*) are balanced and equal, avoiding narrow cut slivers.

Question 19Engineering models, drawings, evidence and project decisions

When laying out two perpendicular reference lines (*axes orthogonaux*) on an out-of-square room floor, what classic geometrical rule does the tiler apply?

  1. The 3-4-5 rule based on the Pythagorean theorem (3 m on one leg, 4 m on the other, yielding a 5 m hypotenuse for a true 90° right angle) Correct answer.
  2. The 2-2-2 rule
  3. Aligning by eye with the most crooked wall
  4. Using a magnetic compass pointed toward magnetic north

Explanation

Room walls are rarely perfectly square. To establish two reference lines meeting at an exact 90° right angle, tilers use the 3-4-5 rule (Pythagoras: 3² + 4² = 9 + 16 = 25 = 5²). Measuring 3 m along one axis and 4 m along the other, the distance between the two points must measure exactly 5 m for the corner to be square.

Question 20Engineering models, drawings, evidence and project decisions

What material must be used to caulk the junction between a floor tile and wall skirting if no baseboard is installed, or between floor and sanitary fixtures?

  1. Rigid cementitious mortar grout
  2. A permanently flexible elastomeric silicone or polyurethane mastic (*mastic élastomère neutre*) Correct answer.
  3. Plaster of Paris
  4. Epoxy resin grout

Explanation

The actual movement-joint specification calls for an appropriate compatible flexible system rather than rigid cement grout. Sealant, backing, geometry, substrate and exposure must match the approved detail; silicone and polyurethane are not automatically interchangeable or suitable for every stone and service.

Question 21Engineering models, drawings, evidence and project decisions

How must structural building expansion joints (*joints de dilatation du gros œuvre*) present in the concrete slab be handled in the tiling installation?

  1. They can be covered over with wire mesh and tiled directly without a joint
  2. They must be strictly respected and carried through the entire screed, adhesive bed, and tile finish in exact vertical alignment, using a specialized preformed profile or elastomeric mastic Correct answer.
  3. They should be filled with hydraulic Portland cement to seal them shut
  4. They should be shifted 50 cm to the side to hide them under a rug

Explanation

Relevant structural movement must be accommodated in the tile assembly through the actual designed joint/detail. Bridging it rigidly can transfer distress into the finish. Exact position, geometry and materials must follow the approved design, not an improvised generic sealant recipe.

Question 22Engineering models, drawings, evidence and project decisions

A living room floor measures 45.0 m². The tiler uses 60x60 cm tiles (0.36 m² per tile) packed 4 tiles per box (1.44 m² per box). Including a 10% allowance for cuts and waste, how many boxes of tiles must be ordered?

  1. 31 boxes
  2. 35 boxes Correct answer.
  3. 40 boxes
  4. 45 boxes

Explanation

The supplied allowance gives45×1.10=49.5m². Each boxcovers4×0.36=1.44m²;49.5/1.44=34.375, so35wholeboxes are needed. This is a supplied ordering model, not a universal waste percentage or a substitute for a cutting layout.

Question 23Engineering models, drawings, evidence and project decisions

What chronic, incurable occupational respiratory disease is caused by prolonged inhalation of airborne dust generated by dry cutting ceramic tiles?

  1. Silicosis (*la silicose*), caused by respirable crystalline silica particles scarring lung tissue Correct answer.
  2. Biliary calculus
  3. Carpal tunnel syndrome
  4. Lactose intolerance

Explanation

Ceramic tiles, porcelain, and mortar contain large quantities of crystalline silica (quartz). Dry cutting or grinding generates respirable crystalline silica (*silice cristalline alvéolaire*), microscopic dust particles that penetrate deep into the alveoli, causing irreversible fibrotic lung scarring known as silicosis (*silicose*), chronic obstructive pulmonary disease (COPD), and lung cancer.

Question 24Engineering models, drawings, evidence and project decisions

In the hierarchy of occupational risk prevention, what collective technical control is required during electric tile cutting before relying on personal masks?

  1. Using wet-cutting diamond saws or tool-shrouded angle grinders connected directly to a certified Class M or H industrial dust extraction vacuum Correct answer.
  2. Opening a small window 20 meters away
  3. Holding one's breath while making each cut
  4. Cutting tiles inside a customer's wardrobe

Explanation

French occupational health regulations (Code du travail) require collective protection at source over individual PPE. Electric cutting tools must be equipped with dedicated dust extraction hoods (*carters d'aspiration*) connected to an M-class or H-class vacuum equipped with automated filter cleaning, or cutting must be performed with wet diamond table saws.

Question 25Tiling substrates, adhesive systems, water management and movement

A bond breaker installed at internal wall/floor and wall/wall junctions before applying a liquid membrane functions to:

  1. Increase adhesion of the membrane to both surfaces
  2. Prevent the membrane bonding across the junction so it can stretch over movement Correct answer.
  3. Act as the final grout
  4. Speed up tile adhesive curing

Explanation

A bond breaker (such as a backing rod or PE tape) stops the membrane sticking right in the corner, leaving a free span that can stretch as the building moves. Without it, the membrane is pinned and tears at the junction when the structure flexes.

Question 26Tiling substrates, adhesive systems, water management and movement

Which substrate sheet is specifically manufactured for wet-area walls and floors and resists moisture better than standard plasterboard?

  1. Standard gypsum plasterboard
  2. Compressed/fibre-cement sheet Correct answer.
  3. MDF panel
  4. Particleboard

Explanation

Fibre-cement (compressed cement) sheeting is dimensionally stable and moisture-resistant, making it the preferred wet-area substrate for tiling over framing. Standard plasterboard degrades when wet and is unsuitable in showers.

Question 27Tiling substrates, adhesive systems, water management and movement

A tiler finds the existing concrete slab to be tiled has a powdery, weak surface layer. The correct action before tiling is to:

  1. Tile straight over it to save time
  2. Remove the friable laitance/loose layer and prepare a sound, clean surface Correct answer.
  3. Add extra adhesive to compensate
  4. Wet it down heavily and tile immediately

Explanation

A weak, dusty laitance layer prevents the adhesive bonding to sound concrete, causing drummy tiles and debonding. It must be mechanically removed (grinding/shotblasting) to expose a sound, clean substrate before priming and tiling.

Question 28Tiling substrates, adhesive systems, water management and movement

Why must a new concrete slab generally be allowed to cure for a period (commonly several weeks) before tiling and applying waterproofing?

  1. To let the colour change
  2. To allow drying shrinkage and most moisture movement to occur before the rigid tile finish is bonded Correct answer.
  3. Because tiles are out of stock
  4. To increase the slab thickness

Explanation

Substrate shrinkage, moisture, stability and curing affect readiness, but elapsed time alone does not establish acceptance. Use the actual system criteria and appropriate tests. No universal waiting period or moisture percentage is supplied by this comparison.

Question 29Tiling substrates, adhesive systems, water management and movement

A flood test of a tiled shower base before tiling (or of the substrate before lining) is carried out to:

  1. Cure the adhesive
  2. Confirm the waterproof membrane and floor waste hold water with no leaks Correct answer.
  3. Test the grout colour
  4. Warm the slab

Explanation

A specified appropriate water test can provide evidence about the relevant membrane/drain arrangement under its test conditions. It does not establish permanent freedom from leaks or replace all other required inspections. Use the approved system procedure, duration and acceptance criteria.

Question 30Tiling substrates, adhesive systems, water management and movement

Tiling directly to a cement render coat on a masonry wall, the render should first be:

  1. Left wet and slippery
  2. Sound, cured, and given a keyed/scratched or primed surface for adhesion Correct answer.
  3. Sealed with gloss paint
  4. Coated with oil

Explanation

The render must be well-cured, sound and free of dust, with a keyed (scratched) or primed surface to give the adhesive a good mechanical and chemical bond. A smooth, dusty or contaminated render leads to drummy tiles.

Question 31Tiling substrates, adhesive systems, water management and movement

An uncoupling (decoupling) membrane laid under floor tiles over a problematic substrate works by:

  1. Adding waterproofing only
  2. Allowing limited in-plane movement between substrate and tiles, reducing stress and cracking Correct answer.
  3. Making the floor warmer
  4. Replacing the adhesive

Explanation

An appropriate uncoupling system can reduce transmission of certain in-plane stresses, within its specified capability. It does not repair every structural defect, accommodate arbitrary out-of-plane movement or guarantee no cracking. Assess the substrate and actual system requirements.

Question 32Tiling substrates, adhesive systems, water management and movement

A self-levelling compound (underlayment) is used before tiling primarily to:

  1. Add fall to a wet-area floor
  2. Produce a smooth, flat substrate over an uneven floor for large or thin tiles Correct answer.
  3. Waterproof the floor
  4. Colour the screed

Explanation

Self-levelling compound flows to a flat, smooth plane over a slightly uneven or rough floor, providing the flatness large-format and thin tiles need to avoid lippage. It is not a falls product and not a waterproofing layer.

Question 33Tiling substrates, adhesive systems, water management and movement

Before tiling over an existing tiled surface, the key checks are that the old tiles are:

  1. The same colour as the new tiles
  2. Sound (not drummy), well-bonded, clean and suitably keyed/primed Correct answer.
  3. Always removed regardless
  4. Heated first

Explanation

Tiling over old tiles is only acceptable when the existing tiles are firmly bonded (not drummy), clean and degreased, and the glaze is keyed or primed so the new adhesive grips. Any loose tiles must be removed and the substrate made good first.

Question 34Tiling substrates, adhesive systems, water management and movement

If a tiled bathroom floor is laid too flat (less than the minimum fall), the most likely defect is:

  1. The tiles cracking immediately
  2. Water ponding on the surface and slow draining Correct answer.
  3. The grout changing colour
  4. The adhesive setting too fast

Explanation

A fall flatter than the 1:80 minimum leaves the surface nearly level, so water collects in puddles and drains slowly or not at all. Ponding causes staining, mould, and slip hazards and is a common warranty defect.

Question 35Engineering models, drawings, evidence and project decisions

When setting out a floor that drains to a central square floor waste, the tiler often sets the grid so that cuts around the waste are formed as four diagonal 'envelope' cuts to:

  1. Avoid using a saw
  2. Create even falls running down to the waste from all sides Correct answer.
  3. Make the tiles larger
  4. Eliminate the need for waterproofing

Explanation

Diagonal (envelope) cuts radiating from a central square floor waste let the four tiled planes each fall toward the drain, giving compound falls so water reaches the waste from every direction without ponding at the corners.

Question 36Engineering models, drawings, evidence and project decisions

A linear (strip) drain is sometimes preferred over a central square waste for large-format tiles because it:

  1. Needs no fall at all
  2. Allows a single-direction fall, so large tiles can be laid without compound diagonal cuts Correct answer.
  3. Is cheaper than any waste
  4. Removes the need for a membrane

Explanation

A linear drain placed against a wall or at the shower entry lets the whole floor fall in one plane toward the strip, so large tiles can be installed flat with a simple single-direction fall instead of four compound falls to a point.

Question 37Tiling substrates, adhesive systems, water management and movement

The PEI rating system for glazed tiles primarily indicates a tile's:

  1. Water absorption
  2. Slip resistance
  3. Surface abrasion (wear) resistance Correct answer.
  4. Breaking strength

Explanation

The PEI (Porcelain Enamel Institute) rating, Classes I to V, ranks a glazed tile's resistance to surface abrasion from foot traffic. PEI I and II are wall-only; PEI III suits residential floors; PEI IV and V suit heavier commercial traffic.

Question 38Tiling substrates, adhesive systems, water management and movement

A glass mosaic sheet on a wall is best fixed with which type of adhesive?

  1. A grey, deeply pigmented cement adhesive
  2. A white, non-staining adhesive suited to translucent glass Correct answer.
  3. Bitumen-based adhesive
  4. Wood glue

Explanation

Translucent glass mosaics show the adhesive through the tile, so a white, non-staining (often C2) adhesive is used to avoid a patchy or grey appearance. Coverage must be even because shadows and trowel marks show through clear glass.

Question 39Tiling substrates, adhesive systems, water management and movement

Natural stone tiles such as marble require special care during fixing and grouting because they:

  1. Are completely non-porous
  2. Can be porous and acid-sensitive, so they stain and etch easily Correct answer.
  3. Cannot be cut with diamond blades
  4. Never need sealing

Explanation

Many natural stones (marble, limestone, travertine) are porous and calcium-based, so they absorb staining liquids and etch when exposed to acids. They are usually sealed before grouting and fixed with non-staining white adhesive.

Question 40Tiling substrates, adhesive systems, water management and movement

For external paving exposed to frost, the most important tile property to specify is:

  1. High water absorption
  2. Low water absorption / frost resistance (e.g. porcelain BIa) Correct answer.
  3. Glossy glaze
  4. Lightest possible colour

Explanation

Frost damage occurs when water absorbed into a porous tile freezes and expands, spalling the tile. Low-absorption, frost-resistant porcelain (Group BIa) is specified for frost-prone external paving so little water is taken up.

Question 41Tiling substrates, adhesive systems, water management and movement

A 'through-body' or full-body porcelain tile is valued for floors because:

  1. The colour runs through the whole thickness, so chips and wear are less visible Correct answer.
  2. It is the cheapest tile available
  3. It cannot be cut
  4. It is only for walls

Explanation

Full-body (through-body) porcelain has the same colour and composition throughout its thickness rather than only a surface glaze, so a chip or worn edge does not expose a contrasting body. This makes it durable for high-traffic and heavy-duty floors.

Question 42Tiling substrates, adhesive systems, water management and movement

A tile labelled with a higher MOR (modulus of rupture) value indicates that the tile has greater:

  1. Water absorption
  2. Bending/breaking strength Correct answer.
  3. Slip resistance
  4. Gloss level

Explanation

Modulus of rupture measures a tile's resistance to bending before it breaks; a higher MOR means a stronger tile better able to span minor voids and resist point loads on floors. It is one of the mechanical properties specified for heavy-duty tiles.

Question 43Tiling substrates, adhesive systems, water management and movement

When tiling a large-format porcelain floor tile, why is back-buttering the tile in addition to combing the bed recommended?

  1. To make the tile lighter
  2. To achieve full adhesive contact/coverage and avoid voids under the tile Correct answer.
  3. To speed up grouting
  4. To remove the need for movement joints

Explanation

Appropriate back-buttering can help achieve the specified contact in a suitable installation, but it does not guarantee coverage by itself. Tile/backing flatness, ridge direction, bedding and actual checks matter. Follow the particular tile/adhesive/system instructions rather than add uncontrolled thickness.

Question 44Tiling substrates, adhesive systems, water management and movement

The size of notched trowel used to spread tile adhesive is chosen mainly according to:

  1. The colour of the grout
  2. The size/flatness of the tile and required bed thickness Correct answer.
  3. The brand of the tile
  4. The room temperature only

Explanation

Larger and flatter-backed tiles need a deeper-notched trowel to deposit enough adhesive for full coverage and to accommodate the tile's footprint, while small mosaics use a fine notch. Matching trowel notch to tile is key to coverage and bed depth.

Question 45Tiling substrates, adhesive systems, water management and movement

Grouting is generally carried out only after the adhesive has set because grouting too early can:

  1. Improve adhesion
  2. Disturb the unset tiles and trap moisture, weakening the bond Correct answer.
  3. Change the tile size
  4. Cure the membrane

Explanation

Grouting before the adhesive has cured can shift tiles out of line, push adhesive up the joints, and seal in moisture that the adhesive needs to release, weakening the bond. The manufacturer's stated set time must be respected.

Question 46Tiling substrates, adhesive systems, water management and movement

The 'open time' of a cementitious tile adhesive refers to the period in which:

  1. The adhesive bag can be stored
  2. The combed adhesive remains workable and will still bond a tile before it skins over Correct answer.
  3. The grout takes to dry
  4. The tiler must finish the whole job

Explanation

Open time concerns placement into spread adhesive under specified conditions before surface changes prevent adequate bonding. It differs from mixed-material pot life. Temperature, airflow, substrate and product requirements affect it; a fresh bucket does not prove every previously spread area remains suitable.

Question 47Tiling substrates, adhesive systems, water management and movement

A tile that has been fixed with the adhesive squeezing up between tiles into the joints causes a problem because it:

  1. Improves grout adhesion
  2. Fills the joint depth so there is insufficient room for grout and the joint may crack Correct answer.
  3. Makes the tile waterproof
  4. Is required by AS 3958

Explanation

Adhesive forced up into the grout joints leaves no depth for the grout, which then sits thin and cracks, and can show through the joint. Tilers keep adhesive out of the joints and rake out any that squeezes up before it sets.

Question 48Tiling substrates, adhesive systems, water management and movement

Efflorescence (a white powdery deposit) appearing on grout joints is caused by:

  1. Too much sunlight
  2. Soluble salts carried to the surface by water moving through the tile bed and evaporating Correct answer.
  3. Using porcelain tiles
  4. Over-sealing the tiles

Explanation

Efflorescence forms when water moves through the bedding/grout, dissolves soluble salts, and deposits them as a white bloom when it evaporates at the surface. Controlling moisture ingress and using low-salt materials reduce it.

Question 49Tiling substrates, adhesive systems, water management and movement

When grouting, excess grout is cleaned off the tile face with a damp sponge, but over-washing the joints too soon will:

  1. Strengthen the grout
  2. Wash cement out of the joints, leaving them weak, pitted and uneven in colour Correct answer.
  3. Speed up curing
  4. Improve slip resistance

Explanation

Sponging too wet or too soon draws cement and fines out of the joints, leaving them low, porous, weak and patchy in colour. The grout should firm up first, and cleaning is done with a well-wrung sponge in light passes.

Question 50Tiling substrates, adhesive systems, water management and movement

A perimeter movement joint at the junction of a tiled floor and a wall is typically filled with:

  1. Rigid cement grout
  2. A flexible (silicone or polyurethane) sealant Correct answer.
  3. Epoxy grout to full hardness
  4. Tile adhesive

Explanation

Perimeter and movement joints must be filled with a flexible sealant such as neutral-cure silicone or polyurethane so the joint can absorb differential movement between the floor and abutting structure without cracking the tiles.