CSLB C-54 Ceramic and Mosaic Tile (Trade Exam) — All Questions

An installer ties a loose-lay shower pan liner to an uncoupling membrane from a different maker, and it leaks. What does industry guidance say about this?

• a.Any two membranes are interchangeable with each other
• b.Mixed systems invite failure outside the warranty✓
• c.Leaks come only from poor tile cutting at the drain
• d.The manufacturer warranty will cover any mixed system

Guidance says combining products or methods from various manufacturers is a recipe for failure that the manufacturer's warranty will not cover, and its example of a pan liner joined to an uncoupling membrane leaked at once. Membranes are not interchangeable, and tile cutting was not the cause.CTEF, wet areas

Why is staying back from the layout chalk line, to avoid mortar squeezing up in the joint, a mistake?

• a.It leaves voids at the tile edges and risks failure✓
• b.It makes the joints too wide to be grouted later
• c.It lets the mortar skin over much sooner
• d.It prevents the tile from being properly beaten in

Guidance says installers who avoid squeeze-up by staying off the chalk line leave dangerous voids that can lead to catastrophic failure. Joint width, mortar skinning and beating in are not what staying back affects.CTEF, troweling

Natural stone tile is set in a dry area to the 95 percent coverage requirement. What limit applies to any single void under it?

• a.No void larger than 6 square inches
• b.No void larger than 2 square inches✓
• c.No void larger than 10 square inches
• d.Larger voids are fine away from the corners

The stone rule allows no voids exceeding 2 square inches, and none within 2 inches of tile corners. Larger limits break the rule, and a size-free allowance outside corners would let a large unsupported area form.ANSI A108.5 via CTEF

What is the first step in troweling thin-set mortar, according to industry guidance?

• a.Comb ridges in a swirling pattern across the whole area
• b.Wet the back of the tile with a sponge first
• c.Key in a thin coat with the flat side of the trowel✓
• d.Press the tile in before the ridges are combed

Keying in a coat with the flat side forces mortar into the substrate for a mechanical bond. Swirled ridges leave voids, wetting the tile back does not replace keying, and setting before combing skips the mortar placement entirely.CTEF, troweling

Which type of mixer does industry guidance say to avoid for tile mortars?

• a.A box mixer✓
• b.A drill with a paddle at about 300 rpm
• c.A bucket mixer fitted with a dust shroud
• d.A low-speed mixing drill

Guidance says to stay away from box mixers because they are not effective for tiling. A paddle drill near 300 rpm is the normal tool, a dust shroud is a suggested accessory, and a low-speed drill is acceptable within the maker's speed range.CTEF, mixing

A tile is set into ridges from a 1/2 x 1/2 inch trowel. About how far should it be slid perpendicular to the ridges?

• a.About 1/8 inch
• b.About 6 inches
• c.Straight down with no sliding
• d.About 1 inch✓

Industry guidance says the tile should move about the width of the notch each way, so a 1/2 inch trowel needs about 1 inch of travel to collapse the ridges. 1/8 inch is too little, 6 inches slides the tile past its spot, and no movement leaves voids between ridges.CTEF, troweling

When setting begins and periodically after that, what should the installer do to check mortar coverage?

• a.Tap each tile with a trowel handle and listen
• b.Lift a tile and look at the mortar contact✓
• c.Check the label on the mortar bag for coverage
• d.Measure the grout joint

Pulling up a tile shows the real coverage on the back and the bed, and guidance says to do this at the start and periodically. Tapping gives only a rough sound, the bag label states the product, and joint width does not measure contact.CTEF, troweling

How does industry guidance say to choose the right trowel notch?

• a.Use one standard notch size for consistency
• b.Pick the smallest notch that avoids squeeze-up
• c.Take the notch size printed on the tile carton
• d.Try different notches and check the coverage✓

Guidance says there is no one-size-fits-all trowel, and the way to decide is to try different notch designs and depths and check the coverage. One notch for all jobs ignores tile differences, the smallest notch sacrifices coverage, and a carton has no coverage test.CTEF, troweling

Wind has skinned the surface of combed mortar before the tile is placed. What should the installer do?

• a.Mist it with water and set the tile
• b.Remove it and comb fresh mortar✓
• c.Press the tile harder into the skin
• d.Set the tile quickly before it dries more

Tile is not to be set on skinned-over mortar, because skinned mortar will not transfer to the back of the tile. Misting, pressing and rushing all leave a weak bond.ANSI A108.5 via CTEF

Does buttering the back of a tile by itself satisfy the mortar coverage requirement?

• a.Yes, it ensures 100 percent coverage on its own
• b.Yes, if the layer is over 1/4 inch
• c.No, only full contact with the substrate counts✓
• d.Yes, but only when used on wall tile

Coverage is the area where mortar contacts both tile and substrate, and a coated back alone does not establish it. A buttered back does not assure contact, extra thickness does not change that, and walls are held to the same test.CTEF, back buttering

Which tool does the VA stone specification call for to tamp and beat stone into the setting bed?

• a.A wooden block or rubber mallet✓
• b.A steel hammer on the face of the stone
• c.A pneumatic chipping hammer
• d.A bare trowel handle

The specification says to tamp and beat stone with a wooden block or rubber mallet, which seats it without damaging the face. A steel hammer or chipping hammer would chip or crack stone, and a trowel handle gives no even seating force.VA 09 63 40

Under the VA specification, how should tile layout be planned around the edges of a room?

• a.Small cuts placed at the center of the room for balance
• b.Cuts split evenly along every wall of the room to keep it level
• c.Any cut size is acceptable as long as each tile sits level
• d.No tile under half size, with cuts at the outer edge✓

The specification lays out the work so that no tile is less than half of full size, and makes all cuts on the outer edge of the field. Cuts at the center or any size produce a poor, unbalanced pattern.VA 09 30 13

What joint width does the VA specification give for glazed wall tile and mosaic tile work?

• a.1/8 inch
• b.1/16 inch✓
• c.1/4 inch
• d.3/8 inch

The specification makes joints 2 mm (1/16 inch) wide for glazed wall tile and mosaic work. 1/8 inch is the porcelain paver maximum, and 1/4 to 3/8 inch is the quarry tile range.VA 09 30 13

For how long should stone grout be kept damp under the VA specification?

• a.24 hours
• b.Seven days✓
• c.Three days
• d.28 days

The specification says to maintain grout in a damp condition for seven days. 24 hours and three days cut the cure short, and 28 days is longer than stated.VA 09 63 40

What does industry guidance suggest to lessen the effect of tile warpage on lippage?

• a.Narrow the grout joint to 1/32 inch
• b.Use a darker grout so it is not noticed
• c.Use a smaller trowel notch
• d.Widen the grout joint✓

Guidance says the joint size should be widened to help lessen the effects of lippage caused by actual warpage. A narrower joint makes lippage more visible, a darker grout only contrasts the edges, and a smaller notch cuts coverage.CTEF, warped tile

A cured epoxy grout in a 1/4 inch joint may have a contoured depression of what depth?

• a.No greater than 1/8 inch
• b.No greater than 3/64 inch✓
• c.No greater than 1/16 inch
• d.The joint must stand slightly raised

Epoxy grout can have a contour of no greater than 3/64 inch (1 mm) for a 1/4 inch joint. 1/8 and 1/16 inch are deeper than the limit, and a raised crown is not what the standard describes.CTEF, grout joints

A crew wants to tint grout on site with pigment to match a tile. What does the VA specification say?

• a.Any pigment may be added to the grout if mixed thoroughly
• b.Pigment is allowed for floor grout but not for wall grout
• c.Pigment may be added only by the manufacturer✓
• d.Pigment is allowed if it is tested first on one joint

The specification allows coloring pigments only at the factory, and job-colored grout is not accepted. A thorough mix, a floor-only exception and a one-joint test are not provisions in it.VA 09 30 13

Which joint finish is generally desired on square-edged tile, including rectified tile?

• a.A recessed joint 1/16 inch below the surface
• b.A raised crown above the tile
• c.A joint filled halfway
• d.A flush joint✓

Guidance says a flush joint is generally desired on any square-edged tile. Recessed, crowned or half-filled joints are failures or defects, and cushion-edge tile is a different case.CTEF, grout joints

Under ANSI movement joint rules, how far must a movement joint opening extend in tilework?

• a.Completely through the tilework to the structural backing✓
• b.Through the tile only, leaving the mortar bed intact below
• c.Only to the top of the setting bed beneath the tile
• d.Halfway through the mortar bed under the tile

Openings for movement joints must go completely and directly through tilework down to structural backing. Cutting only the tile or part of the bed leaves a hard path that carries movement into the tile.CTEF, honoring expansion joints

What must be present at changes of plane, such as inside corners and floor-to-wall transitions, according to industry guidance?

• a.A fully grouted rigid joint
• b.A clean, straight, open joint✓
• c.A mortar fillet in each corner
• d.Tile edges butted tightly together

Guidance says there must be a clean, straight, open joint at all changes of plane, to be filled with a flexible sealant. Rigid grout, a mortar fillet or butted tile edges would transfer movement into the tile.CTEF, movement joints

When tooling a freshly applied sealant joint in tile, what does one method in industry guidance spray on the sealant and tile face?

• a.Mineral spirits applied with a rag
• b.An acid cleaner diluted with water
• c.Straight acetone from a spray bottle
• d.Water mixed with dish detergent✓

The method sprays the sealant and the tile face with water and dish detergent so the sealant can be tooled smooth. Mineral spirits, acid cleaner and acetone are not part of that method and can harm sealant or surfaces.CTEF, movement joints

Which statement about movement in tile installations does industry guidance make?

• a.All installations move with temperature and humidity✓
• b.Only exterior installations move to a meaningful degree
• c.Only commercial installations move to any extent
• d.Only tile over a wood subfloor moves at all

Guidance says all tile installations, residential and commercial, move with temperature and humidity. Exterior-only, commercial-only or wood-only movement are all too narrow.CTEF, top ten requirements

Efflorescence is on the grout. When is an acid cleaner appropriate?

• a.Always, as the first treatment on any white powder
• b.Only on glazed wall tile
• c.Only when the manufacturer recommends one✓
• d.Whenever the white powder returns

Guidance says to use an acid cleaner only if the manufacturer recommends it, since acid used too early or too strongly can damage grout and glazed surfaces. Using it on every return does not remove the cause, which is moisture.CTEF, efflorescence; UFGS 09 30 10

A breathable sealer is applied over efflorescence. What does industry guidance say it does?

• a.It permanently removes the salts from the grout joints
• b.It stops water in the slab from moving upward
• c.It makes repair of the grout and tile unnecessary
• d.It may slow moisture but will not solve the cause✓

A breathable sealer may slow the travel of moisture, but the source of the water must still be eliminated. It does not remove salts or stop all water, and it is no replacement for repair.CTEF, efflorescence

Dark, damp-looking grout lines appear on shower wall tile. What is the usual cause and cure?

• a.Wrong grout color; regrout the joints in a lighter color
• b.Hard water spotting; apply a topical sealer over the grout
• c.Too much sealer; wash the wall and reseal
• d.Mortar voids at the tile edges; replace the tile✓

The cause is mostly a lack of full mortar coverage on the back edges, so water collects and bleeds through the grout. Guidance says there is no fix except removal and replacement, so sealing, recoloring or topical coats treat only the symptom.CTEF, mortar coverage

What does mortar left to dry inside a movement joint create?

• a.A flexible joint that actually works better
• b.A watertight seal against moisture entry
• c.A rigid joint that stops the installation from moving✓
• d.A stronger and more protected tile edge

Guidance says mortar left in the joint creates a hard joint that defeats the purpose of allowing the installation and the structure to move. It does not make the joint flexible, seal it against water, or strengthen the tile edge.CTEF, radiant heating (movement joints)

Under the VA specification, what is done with tile that is out of plane or misaligned?

• a.Grind the high edges flat
• b.Leave it if the grout hides it
• c.Remove and reset it✓
• d.Fill the low side with grout

The specification calls for removing and resetting tiles that are out of plane or misaligned. Grinding or hiding with grout does not correct the setting.VA 09 30 13

Which condition does the VA specification say completed work must be free from?

• a.Hollow-sounding areas and loose or cracked tile✓
• b.Joints of uniform width and consistent finish
• c.Grout flush with the tile surface along the joints
• d.Cut tile placed at the outer edge of the field

The specification calls for completed work free from hollow-sounding areas and loose, cracked or defective tile. Uniform joints, flush grout and edge cuts are normal features of acceptable work.VA 09 30 13

A failed caulk joint is replaced using the same product that failed. What is likely to happen?

• a.It will last longer because it is new
• b.The joint will fail the same way again✓
• c.It will bond better to dirty tile
• d.It will harden into a flexible joint

Repeating the same product with the same movement repeats the failure, so a suitable sealant such as silicone should be chosen. New material does not fix a wrong material, and bonding to a dirty surface is poor.CTEF, movement joints

What do tile professionals call the confirmation of a suspected shower defect by taking the shower apart?

• a.Thermal imaging survey
• b.Destructive testing✓
• c.Moisture meter mapping
• d.A flood test of the pan

Guidance notes that confirming an analysis by dismantling the shower is called destructive testing. Thermal imaging, moisture mapping and flood tests leave the assembly in place.CTEF, shower discoloration

Which instrument is often used to view the heat signature of electric heating wires beneath tile?

• a.A thermal imaging camera✓
• b.A moisture meter probe set
• c.A level and a long straightedge
• d.A UV lamp held over the floor

A FLIR thermal imaging camera shows where heat is or is not being produced. A moisture meter and straightedge measure other things, and a UV lamp shows nothing about wire heat.CTEF, radiant heating

A heated tile floor has a cut heating cable. What is a typical cause?

• a.A utility knife used to clean out the joints✓
• b.Over-wetting the grout when cleaning the surface
• c.Using a larger notched trowel on a heated floor
• d.A thermostat set too high for the tile

Cut cables are usually caused by cleaning joints with a utility knife before grouting, and screws driven through cables are another cause. Wet grout, trowel size and thermostat setting do not cut a cable.CTEF, radiant heating

A homeowner wants new tile over a wall with a suspected moisture leak behind it. What does industry guidance say about tiling over a water problem?

• a.Tiling will seal the leak behind the wall for good, so no repair is needed
• b.A coat of sealer under the tile will manage the moisture problem
• c.Tiling does not cure it; the source must be found and fixed✓
• d.Wait a few weeks to see whether the leak stops by itself

Guidance says tiling over a water problem does not make it go away, and any water issue must be examined and resolved first. Tile does not seal a leak, and waiting leaves the source active.CTEF, water leaks

When a cracked tile from ignored movement joints causes a callback, who typically bears the cost of the repair, according to industry guidance?

• a.The owner, as ordinary wear and tear
• b.The tile manufacturer under warranty
• c.The installer, at his or her own expense✓
• d.The mortar supplier as a goodwill gesture

Guidance describes a callback in which the installer must repair the cracked tile at his or her own expense, hoping matching tile is available. The owner, manufacturer and mortar supplier did not skip the joints.CTEF, honoring expansion joints

A round dull mark appears on polished marble where a glass once sat. What is the likely cause?

• a.Mortar showing through the stone
• b.Etching from a spilled acidic liquid✓
• c.Grout haze left on the surface
• d.Lippage between adjacent tiles

A dull ring on polished stone is typically etching from an acidic liquid, and a penetrating sealer may reduce the chance. Mortar, grout haze and lippage would not produce a ring in the shape of a glass base.CTEF, sealers

A client wants new tile laid over an existing floor with cracked tiles. What does industry guidance say about the cracks?

• a.They are cosmetic only and need no further checking
• b.They can be fixed by filling them with caulk before the new tile goes down
• c.They show only that the grout is old and worn
• d.They may signal hidden problems only full removal confirms✓

Cracks in an existing installation may reflect problems that are almost impossible to see, verified only by completely removing the old system. Calling them cosmetic or caulking them ignores the cause.CTEF, tile over tile

What is the maximum slope per foot to a shower drain under the plumbing code, as described by industry guidance?

• a.1/2 inch per foot✓
• b.1/8 inch per foot
• c.1 inch per foot
• d.1/4 inch per foot

The code calls for a minimum of 1/4 inch and a maximum of 1/2 inch per foot. 1/8 inch is too flat, 1 inch is far steeper than allowed, and 1/4 inch is the minimum, not the maximum.CPC via CTEF

Besides slope, what must a shower floor be so that water does not collect?

• a.Level in both directions
• b.Roughened by hand
• c.Concave at the center
• d.Flat, with no low spots✓

Guidance says the floor must also be flat, with no low spots, or birdbaths will retain water. A level floor has no fall to the drain, hand-roughening does not drain water, and a concave center holds it.CTEF, slope to drain

Which other shower surfaces must slope toward the drain besides the floor?

• a.None, since only the floor drains
• b.Curbs, niche shelves, seats and sills✓
• c.Only the curb at the shower entry
• d.Only surfaces wider than 12 inches

Guidance says all horizontal surfaces, including the curb or threshold, niche shelves, corner and shaving shelves, seats and windowsills, must slope to the drain. A floor-only rule, a curb-only rule or a width threshold are not in it.CTEF, slope to drain

How thick is the mortar bed above a shower pan membrane at the walls compared with the drain?

• a.Thicker at the walls
• b.Thicker at the drain
• c.Tapered to nothing at the drain
• d.The same thickness✓

The pre-slope below the membrane gives the fall, and the bed above it is the same thickness at the walls as at the drain. A bed that varies would change the slope of the surface.CTEF, slope to drain

Which receptacle protection does a city handout require for all receptacle outlets in bathrooms?

• a.AFCI protection only
• b.A dedicated 30-amp circuit
• c.Tamper-resistant covers only
• d.GFCI protection✓

The handout requires all bathroom receptacle outlets to be GFCI protected. AFCI protection addresses arc faults rather than shock near water, a 30-amp circuit is not required by it, and tamper-resistant covers alone do not give ground-fault protection.City of San Bruno handout (2025 codes)

A city handout requires nonabsorbent finish on shower compartment walls to what minimum height above the floor?

• a.4 feet
• b.6 feet✓
• c.5 feet
• d.8 feet

The handout requires nonabsorbent walls to at least 6 feet above the floor. 4 and 5 feet are too low, and 8 feet exceeds the stated minimum.City of Milpitas handout (2025 codes)

How deep is the water for a shower pan test, according to one city's handout?

• a.1/2 inch
• b.2 inches✓
• c.1 inch
• d.6 inches

The handout says shower pan tests must have 2 inches of water sitting for at least 24 hours. 1/2 and 1 inch are too shallow, and 6 inches is deeper than stated.City of Rancho Palos Verdes handout (2025 codes)

According to a city handout, a shower pan lining must be free of nails and perforations up to what height?

• a.Even with the top of the finished dam or threshold
• b.1/4 inch above the finished dam or threshold
• c.1 inch above the finished dam or threshold✓
• d.No height is set for it in the handout

The handout says no nails or perforations to a height at least 1 inch above the finished dam or threshold, so a fastener can never sit at the water line. A liner free only to the dam top, or to 1/4 inch above it, is too low, and the handout does set a height.City of Milpitas handout (2025 codes)

What must be done about subdrain weep holes in a shower pan?

• a.Seal them with caulk
• b.Fill them with thin-set
• c.Protect them from clogging✓
• d.Cover them with the pan liner

Weep holes must be protected from clogging so moisture can drain. Caulk, thin-set and liner would close them.City of Milpitas handout (2025 codes)

What type of glass does a city handout require for shower doors and partitions?

• a.Annealed float glass of any thickness
• b.Safety glass, tempered or laminated✓
• c.Wired glass rated for fire doors
• d.Acrylic of any grade or thickness

Safety glass, tempered or laminated, is required for all glass shower doors and partitions. Annealed float glass breaks into sharp shards, wired glass is a fire-rated product, and acrylic is not the stated material.City of San Bruno handout (2025 codes)

What live load must curbless shower receptor floor framing support, per one city's guideline?

• a.10 psf
• b.20 psf
• c.100 psf
• d.40 psf✓

The guideline requires framing to support a 40 psf live load and a minimum 20 psf dead load. 10 psf is too low, 20 psf is the dead load figure, and 100 psf is not stated.City of Mill Valley curbless shower guideline

A curbless shower receptor must hold how much water above the drain inlet without spilling over the threshold, per one city's guideline?

• a.6.9 gallons
• b.96 gallons
• c.9.6 gallons✓
• d.0.96 gallons

The guideline sets a minimum of 9.6 gallons above the top of the drain inlet. 0.96 and 96 gallons are off by a decimal place, and 6.9 gallons transposes the digits.City of Mill Valley curbless shower guideline

Which TCNA Handbook method covers a continuous-use steam shower installation?

• a.F250
• b.EJ171
• c.F128
• d.SR613✓

SR613 refers to the details and best practices for a continuous-use steam shower. F250 is the stone-over-wood method, EJ171 covers movement joints, and F128 is an electric radiant heating method.TCNA Handbook via CTEF

Which backer does a city handout say cannot receive tile directly in a shower?

• a.Cement backer board with seams taped and filled
• b.Fiber-cement board with sealed and taped joints
• c.Water-resistant gypsum board (purple board)✓
• d.Glass-mat gypsum backer with a waterproof coating

The handout says purple board cannot be used in a shower for direct application of tile, while cement, fiber-cement and glass-mat gypsum backers are acceptable.City of Rancho Palos Verdes handout (2025 codes)