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

Which is one of the three jobs thin-set mortar does in a tile assembly?

• a.Levels an uneven slab
• b.Supports the tile✓
• c.Waterproofs the substrate
• d.Colors the grout joint

Mortar bonds to the substrate, supports the tile and bonds to the tile back. It is not a leveling or waterproofing material.CTEF, troweling

What happens during the slaking step of mixing mortar?

• a.The mix rests✓
• b.Latex is poured on top
• c.Extra water is added
• d.It is mixed at high speed

Mixing has three phases: initial mix, slaking (the materials rest) and remixing. Adding water during slaking changes the mix the maker designed.CTEF, mixing

An installer mixes thin-set at high drill speed. What problem does industry guidance warn about?

• a.Better flow into the notches
• b.Air whipped in, weakening it✓
• c.No effect on strength
• d.Faster curing and better bond

Speeds above about 300 rpm can whip or entrain air, making the mortar light and weak. Faster mixing does not improve bond.CTEF, mixing

What minimum mortar thickness must remain between tile and backing after the tile is beaten in?

• a.3/32 inch✓
• b.1/4 inch
• c.1/2 inch
• d.1/32 inch

The ANSI method requires sufficient mortar for a minimum of 3/32 inch after embedding. 1/4 inch is the typical maximum for thin-set.ANSI A108.5 via CTEF

For 8 × 48 inch planks, which way should the trowel ridges run?

• a.In circles
• b.Diagonally
• c.Parallel to the 48-inch side
• d.Parallel to the 8-inch side✓

Ridges run in the same direction as the short side so trapped air has the shortest path to escape.CTEF, troweling

What minimum coverage applies to porcelain tile on an exterior wall?

• a.85 percent
• b.80 percent
• c.70 percent
• d.95 percent✓

ANSI A108.5 raises the 80 percent minimum to 95 percent on exterior and shower installations.ANSI A108.5 via CTEF

Under the TCNA Handbook's stone rule, where may no voids occur under natural stone tile?

• a.Within 6 inches of the edges
• b.Only at the center
• c.Anywhere under dry-area tile
• d.Within 2 inches of corners✓

Stone requires 95 percent coverage with no void over 2 square inches and none within 2 inches of the corners.TCNA Handbook via CTEF

For which tile does industry guidance recommend back buttering?

• a.Glass tile✓
• b.Small unglazed mosaics on a dry floor
• c.Tile set in organic adhesive
• d.Any 4 × 4 wall tile

Back buttering is recommended for large format tile, glass tile, natural stone and exterior tile. It adds bond, not coverage.CTEF, troweling

Why does industry guidance advise against a V-notch trowel for setting floor tile?

• a.It leaves too much mortar
• b.Too little support✓
• c.It scratches porcelain
• d.It is only for epoxy

The narrow point of V-notch mortar does not provide the coverage needed to support the tile. The tempting belief that it leaves excess mortar is backward.CTEF, troweling

A 6 × 24 plank will be set in running bond. Without a manufacturer's other limit, what is the maximum offset?

• a.10 percent
• b.33 percent✓
• c.66 percent
• d.50 percent

ANSI A108.02 limits offsets to 33 percent where the offset side exceeds 15 inches, unless the manufacturer specifies otherwise. 50 percent amplifies warpage.ANSI A108.02-4.3.8.2 via CTEF

A porcelain floor has 1/16 inch grout joints. What is the allowable lippage?

• a.1/16 inch
• b.3/16 inch
• c.1/8 inch
• d.1/32 inch✓

For joints from 1/16 to under 1/4 inch, allowable lippage is 1/32 inch; 1/16 inch applies to joints 1/4 inch and wider.ANSI A108.02 via CTEF

What is the absolute minimum grout joint width under ANSI A108.02?

• a.1/8 inch
• b.1/32 inch
• c.No minimum
• d.1/16 inch✓

In no circumstances shall the grout joint be less than 1/16 inch, and it must also be at least three times the tile's size variation.ANSI A108.02-4.3.8 via CTEF

A 20 × 20 inch rectified tile is being set. What average minimum grout joint does ANSI require?

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

Tiles with any side over 15 inches need an average minimum of 1/8 inch if rectified and 3/16 inch if calibrated.ANSI A108.02-4.3.8.1 via CTEF

What tool is used to pack 100 percent solids epoxy grout into the joints?

• a.Hard rubber float✓
• b.A caulk gun
• c.A margin trowel
• d.A soft sponge

A118.3 epoxy grout is installed with sufficient pressure using a hard rubber float. A soft sponge or float pulls grout out of joints.ANSI A118.3 via CTEF

When should cleanup begin on a portland cement grout?

• a.Immediately, while wet
• b.After it sets up✓
• c.After 7 days of curing
• d.Only after acid washing

Cement grout must set up so moisture can hydrate out before cleaning; washing too early pulls grout from the joints.CTEF, low grout joints

A white tile floor is grouted in a contrasting dark gray. What does the NTCA Reference Manual say about the result?

• a.It emphasizes variations✓
• b.It hides size variations
• c.It makes lippage disappear
• d.It has no visual effect

A contrasting grout emphasizes the joint and any variation in tile size and position; a matching grout de-emphasizes them.NTCA Reference Manual via CTEF

A slab has a 1/2 inch expansion joint under a new tile floor. How wide must the tile's movement joint be?

• a.No joint is needed
• b.At least 1/2 inch✓
• c.At least 1/4 inch
• d.Grout-joint width only

Joints through tile over structural joints must never be narrower than the structural joint.TCNA Handbook via CTEF

Under the VA specification, what space is left at the lip of a tub where backer board meets it?

• a.No space; butt it tight
• b.1/16 inch for thin-set
• c.1 inch for grout
• d.1/4 inch for sealant✓

The VA specification leaves a 1/4 inch space for sealant at lips of tubs, sinks and plumbing receptors.VA 09 30 13

What is the purpose of a foam backer rod in a sealant joint?

• a.Hold grout in place
• b.Waterproof the substrate
• c.Fill the joint instead of sealant
• d.Set depth; stop three-sided bond✓

Backing forms a joint enclosed on three sides at the specified depth, and sealant must bond only to two opposing surfaces.VA 07 92 00

A sealant joint is 1/4 inch wide. How deep should the sealant be under the VA specification?

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

At widths up to 1/4 inch, sealant depth equals width. Half-depth applies only to wider joints.VA 07 92 00

Why do acrylic latex caulks fail in tile movement joints, according to industry guidance?

• a.They stain the grout
• b.They are too flexible
• c.They cure too slowly
• d.They harden and shrink✓

Acrylic and siliconized latex caulks dry hard, shrink and fall out when the structure moves. Silicone, urethane and polysulfide are suitable.ANSI A108.01 via CTEF

White powder appears on grout lines over a slab-on-grade after a wet winter. What does it indicate?

• a.Grout that was mixed too dry
• b.Water carrying up minerals✓
• c.A sealer that is curing
• d.Normal cement dust

Efflorescence requires water to carry minerals to the surface, evaporate and leave salts. The water source must be found.CTEF, efflorescence

Under the VA stone specification, how is a damaged stone repaired?

• a.Per the stone producer✓
• b.With any color-matched epoxy
• c.By sanding it flat
• d.By sealing over the damage

Stone is repaired using methods recommended by the stone producer, and replacement stone must not show evidence of replacement.VA 09 63 40

A heated tile floor fails where a toilet was bolted down after tiling. What is the likely cause?

• a.Grout that is too thick
• b.A fastener hit the cable✓
• c.A thermostat set too low
• d.Tile that is too dense

Screws and fasteners from later trades, such as toilet bolts and door stops, are a common cause of heating cable failures.CTEF, radiant heating

A new tile floor over concrete floods 20 days after installation. What does industry guidance recommend?

• a.Ask the mortar maker✓
• b.Tear out all tile at once
• c.Seal the grout immediately
• d.Ignore it; tile is waterproof

For installations within 28 days of flooding, contact the setting materials manufacturer for an opinion on how to proceed.CTEF, flooded installations

Which shower size fails the California minimum listed in city handouts for the 2025 codes?

• a.30 × 60 inches
• b.36 × 36 inches
• c.30 × 30 inches✓
• d.32 × 32 inches

A compartment needs at least 1,024 in² and a 30-inch circle; 30 × 30 is only 900 in². A 30 × 60 receptor is exempt.CPC shower size per city handouts (2025 codes)

What minimum drain and trap size do city handouts list for a shower?

• a.2 inches✓
• b.3 inches
• c.1-1/4 inches
• d.1-1/2 inches

Showers require a minimum 2-inch drain and trap; tub-to-shower conversions increase smaller waste outlets to 2 inches.CPC per city handouts (2025 codes)

A tiled niche shelf in a shower is set dead level. What does the ANSI standard require?

• a.Slope it away from the drain
• b.Seal it instead of sloping
• c.Level is correct for shelves
• d.Slope it toward the drain✓

All horizontal ledges and rims shall slope so fluid flows toward the drain, and TCNA details extend this to seats, sills and curbs.ANSI A108.01-3.6.4 via CTEF

Why does the TCNA Handbook require a pre-slope under the pan liner of a clamping-ring drain shower?

• a.To thicken the tile bed
• b.To hold the liner flat
• c.To feed the weep holes✓
• d.To replace the mortar bed

The sloped fill under the liner lets water that passes the tile reach the drain's weep holes; without it, trapped water eventually smells.TCNA Handbook via CTEF

What slope do industry sources give for a steam shower bench?

• a.1/4 inch per 12 inches to the drain✓
• b.2 inches per foot
• c.Level
• d.1 inch per foot away from the drain

Benches and horizontal surfaces in a steam shower slope 1/4 inch per 12 inches to the drain; 2 inches per foot is the ceiling slope.TCNA SR613 via CTEF

How thick is the mortar bed placed on top of a shower pan liner under ANSI A108.01A?

• a.Thicker at the drain
• b.Tapered from 3 inches to zero
• c.A uniform 1-1/2 inches✓
• d.1/4 inch

The mortar bed over the membrane is the same thickness at the walls and at the drain, 1-1/2 inches; the pre-slope below provides the pitch.ANSI A108.01A via CTEF

In one California city's curbless-shower guideline, where must the top of the drain inlet sit?

• a.At least 1/2 inch above the floor
• b.Level with the threshold
• c.2 inches below the threshold top✓
• d.Anywhere, if sloped

The guideline requires the drain inlet top to be a minimum of 2 inches below the top of the finished threshold, so the receptor holds water.City of Mill Valley curbless shower guideline

A homeowner reports a musty odor from a shower that does not leak. What does industry guidance link this to?

• a.Epoxy grout
• b.Glass tile
• c.Too much grout sealer
• d.No pre-slope✓

Without a pre-slope, trapped and stagnant water on the liner eventually emits an offensive odor even if nothing leaks.CTEF, slope to drain

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