ACT Mortar (Mud) Walls

Which TCNA Handbook method covers tile installation over a Portland cement plaster scratch and brown coat applied to metal lath on a wall?

• AW201
• BW244
• CF113
• DB414

Why is a cleavage membrane installed behind metal lath in TCNA Method W201?

• ATo bond the mortar bed to the structural wall
• BTo isolate the mortar bed from substrate movement and protect the backing from moisture
• CTo replace the need for a separate vapor barrier
• DTo increase the strength of the mortar bed

TCNA Method W221 is selected when the existing wall substrate is which of the following?

• AA flat, plumb, structurally sound surface ready for direct-bond tile
• BSeverely out-of-plumb or out-of-flat and requires a thicker mortar bed for correction
• CAn exterior glazed brick veneer in a freeze-thaw climate
• DA waterproof shower receptor pre-formed in resin

An installer applies a Portland cement plaster scratch and brown coat directly over moisture-resistant gypsum board to true a wall before tile. Which TCNA wall method describes this assembly?

• AW201
• BW221
• CW222
• DW244C

Which of the following is the most accurate description of TCNA Method W244C?

• AThick-bed mortar over metal lath with cleavage membrane
• BThin-set tile installation over cementitious backer units on wood or metal studs
• CDirect-bond tile to moisture-resistant gypsum board in dry areas only
• DFloat mortar bed bonded directly to CMU without lath

In TCNA W201, the metal lath is installed so that the cups (open mesh openings) face which direction on a wall?

• ADownward, so mortar slides off cleanly
• BUpward, so the cups hold and key the mortar
• CFlat against the substrate with no orientation requirement
• DEither direction; only fastener spacing matters

What is the minimum expanded metal lath weight specified for wall mortar bed applications under TCNA wall methods?

• A1.75 pounds per square yard
• B2.5 pounds per square yard
• C3.4 pounds per square yard
• D5.4 pounds per square yard

When using 2.5 lb expanded diamond-mesh lath on a wall under TCNA W201, which fastener spacing along studs is most appropriate?

• AEvery 4 inches along each stud
• BEvery 6 inches along each stud
• CEvery 16 inches along each stud
• DAt top and bottom of the sheet only

On a wood-stud wall under TCNA W201, what minimum penetration into the framing should each lath fastener achieve?

• A1/4 inch
• B1/2 inch
• C3/4 inch
• D1 inch

Behind the metal lath in TCNA W201, the installer must place a continuous moisture-control layer. Which material is most commonly specified?

• A6 mil polyethylene sheet with no overlap
• B15 lb (No. 15) asphalt-saturated roofing felt or 4 mil polyethylene, lapped 2 inches hori…
• CSelf-adhered roofing membrane stapled to the studs
• DLatex paint coating on the studs

Which finish of metal lath is required for tile mortar bed applications in damp or wet locations?

• AMill (black) steel lath
• BGalvanized (zinc-coated) lath
• CPainted steel lath
• DAluminum lath

When lapping adjacent sheets of expanded metal lath on a wall, the recommended minimum side lap and end lap are:

• A1/2 inch sides, 1 inch ends
• B1 inch sides, 2 inches ends
• C2 inches sides, 2 inches ends, tied at the lap
• DNo lap required if sheets butt tightly

Self-furring diamond mesh lath is used on walls to:

• AEliminate the need for any moisture barrier
• BHold the lath approximately 1/4 inch off the substrate so mortar can fully embed behind t…
• CAllow direct bonding of the lath to the structural wall
• DIncrease the weight of the bed by 50%

How many strands of metal lath should each fastener engage when fastening lath to studs?

• AOne strand
• BAt least two strands
• CAt least three strands
• DAt least five strands

Which fastener type is acceptable for attaching metal lath through a vapor barrier to wood studs in a tile mortar bed wall assembly?

• AStandard interior drywall screws
• BGalvanized roofing nails or galvanized lath staples of sufficient length
• CAluminum brads
• DSmooth-shank steel finish nails

On metal stud framing, lath is most often attached with which type of fastener?

• AHot-dipped galvanized roofing nails
• BSelf-drilling, self-tapping pan-head screws compatible with the stud gauge
• CPowder-actuated fasteners only
• DConstruction adhesive in lieu of mechanical fasteners

What Portland cement plaster mix is typically specified for the scratch coat of a wall mortar bed?

• A1 part cement to 1 part sand by volume
• B1 part cement to 2 to 3 parts sand by volume
• C1 part cement to 6 parts sand by volume
• DPure cement paste with no sand

Type S masonry cement is sometimes used to make a mortar bed because it provides:

• AA faster set than Portland cement scratch coats
• BBuilt-in plasticizers and a balanced cement-lime mix for workability and bond
• CHigher compressive strength than Portland-sand mixes
• DInherent waterproofing without a membrane

Adding a latex (polymer) admixture in lieu of part of the gauging water in a Portland cement scratch and brown coat primarily:

• AIncreases bond strength and reduces water absorption
• BReplaces the need for metal lath
• CAllows tile to be applied within 30 minutes
• DEliminates the need for movement joints

Sand for a wall mortar bed should generally meet which gradation standard?

• AASTM C144 graded masonry sand
• BASTM C33 concrete coarse aggregate
• CDune or beach sand with rounded grains
• DCrusher fines with up to 20% silt

What is the most common reason mortar bed mixes fail prematurely in wall applications?

• AUsing galvanized lath instead of mill-finish lath
• BExcessive water (over-tempering) in mixing or retempering
• CUsing sand graded per ASTM C144
• DApplying scratch and brown coats on the same day

Retempering a mortar bed batch with additional water is:

• AAlways permitted because mortar bed work is forgiving
• BPermitted only to restore workability lost to evaporation, never to revive set mortar, an…
• CStrictly prohibited under all TCNA wall methods
• DRequired after every 30 minutes of placement

Which ANSI specification governs the dry-set Portland cement mortars commonly used as the bond coat between the cured float bed and the tile?

• AANSI A118.1
• BANSI A118.6
• CANSI A118.9
• DANSI A118.12

Why is potable water specified for mixing mortar bed cement?

• AIt looks cleaner on the jobsite
• BNon-potable water can introduce salts, organics, or acids that affect set and durability
• CLocal codes always prohibit non-potable water
• DPotable water sets faster

Which set of practices keeps a wall mortar bed mix at consistent quality across a workday?

• ABatch by volume with a measured bucket or box, keep sand under a tarp, use potable water,…
• BMix by shovel-count using bagged cement and any nearby sand
• CUse leftover thinset mixed with sand
• DPre-mix and store batches in sealed buckets overnight for next-day use

Cement-lime mortar (ASTM C270 Type S) used for a mortar bed contains, by volume, approximately:

• A1 part Portland cement, 0 parts lime, 3 parts sand
• B1 part Portland cement, 1/4 to 1/2 part hydrated lime, 3-1/2 to 4-1/2 parts sand
• C2 parts Portland cement, 1 part lime, 8 parts sand
• DNo Portland cement, 1 part lime, 3 parts sand

When mixing a Portland cement mortar bed with a paddle mixer, mortar should be allowed to slake (rest) for approximately:

• ANo rest is needed
• B5 to 10 minutes, then remix briefly
• C30 to 45 minutes before use
• DOvernight

The brown (float) coat of a wall mortar bed is typically:

• ARicher in cement than the scratch coat
• BSimilar to or slightly leaner than the scratch coat in cement content
• CPure lime
• DIdentical in composition to the bond coat that follows

Which property of a properly proportioned wall mortar bed is most important to long-term tile bond?

• AMaximum compressive strength regardless of shrinkage
• BBalanced strength, low shrinkage, and a textured surface compatible with the chosen bond…
• CHigh water absorption so the bond coat sticks
• DA smooth, polished steel-troweled finish

An installer is mixing a wall scratch coat. Approximately how should the mortar drape from the trowel when correctly tempered?

• APour like a slurry off the trowel
• BHang in a soft ridge, slightly stiff, that does not slough off a vertical lath
• CCrumble dry off the trowel
• DStick to the trowel and refuse to release at all

Beyond a richer cement ratio, the scratch coat differs from the brown coat principally because it is:

• AFinished with a steel trowel to a polished surface
• BCombed or scratched with horizontal grooves while still plastic to provide a mechanical k…
• CAlways thicker than the brown coat
• DAllowed to cure for at least 7 days before any further work

Approximately what thickness is the scratch coat in a wall mortar bed assembly?

• A1/16 inch
• BApproximately 3/8 inch (1/4 to 1/2 inch range)
• C1 inch
• DWhatever is needed to bring the wall plumb

What is the typical total thickness of a wall mortar bed (scratch + brown coats combined) under TCNA W201?

• A1/8 inch
• BApproximately 3/4 inch
• C1-1/2 to 2 inches
• DWhatever the substrate happens to need with no maximum

Approximately how long should the scratch coat be allowed to cure before the brown coat is applied?

• AApply the brown coat immediately while the scratch coat is still wet
• BAllow the scratch coat to reach initial set; many specifications call for moist-curing th…
• CWait a minimum of 7 days
• DCure for 28 days like structural concrete

Which surface texture is correct for the cured brown coat that will receive a bond coat and tile?

• APolished, steel-troweled glossy surface
• BHard, plumb, flat surface with a uniform sandpaper-like texture (typically wood- or spong…
• CHeavily grooved with horizontal striations like the scratch coat
• DLoose, dusty surface with surface laitance

Approximate maximum per-lift thickness for the brown coat is:

• A1/16 inch
• BAbout 5/8 inch per lift
• C1-1/2 inches per lift
• DUnlimited if the lath holds it

When the brown coat is built up in multiple lifts to correct a severely out-of-plumb wall, the installer should:

• APolish each lift smooth before the next
• BScore or scratch each intermediate lift before the next lift is applied
• CAllow each lift to dry fully and dust before adding the next
• DApply each lift in vertical bands and never horizontal

Which tool is the primary device the installer uses to bring the brown coat plumb and flat?

• ASharp pointing trowel
• BLong darby or featheredge (rod) screeded against vertical and horizontal floats/screeds
• CSmall margin trowel
• DNotched trowel

Screed rails or floated guide strips placed plumb on a wall are used to:

• AReplace the need for a level or straightedge
• BEstablish the finished plane that the brown coat will be screeded to
• CConceal poor lath fastening
• DLimit the curing of the bed

If the brown coat dries too quickly in hot weather before it has gained strength, the most likely defect is:

• AExcess polymer migration
• BPlastic shrinkage cracking and weak surface dusting
• CGalvanic corrosion of the lath
• DLoss of vapor barrier function

After the brown coat has cured to a hard, plumb surface, before the bond coat is applied, the installer should:

• AApply a curing compound to seal the surface
• BLightly dampen the surface and remove any laitance or loose material
• CCoat the entire surface with latex primer
• DApply a thinned coat of paint as a bond agent

Tile may be set into a wall mortar bed while the bed is 'green'. What does that mean?

• AThe bed is at least 28 days old and fully cured
• BThe bed has just been floated and is still plastic enough to receive tile pressed directl…
• CThe bed has been painted green for inspection
• DThe bed has been chemically treated with green dye

Two installers debate how to test the scratch coat for set before applying the brown coat. The correct field check is:

• APressing a thumb in deep enough to leave a mark
• BScratching the surface lightly with a nail or screwdriver; the surface should resist scra…
• CPouring a cup of water and timing absorption
• DStriking the surface with a hammer to test for hardness

Moist-curing the brown coat for an extended period in hot, dry weather principally:

• AIncreases compressive strength and reduces shrinkage cracking
• BSlows the working time of the bond coat
• CChanges the color of the cured mortar to gray
• DReduces the need for movement joints

TCNA Handbook industry standard for a finished tile substrate plane on a wall under standard (≤15 inch edge) tile is no more than:

• A1/2 inch in 10 feet
• B1/4 inch in 10 feet
• C1/8 inch in 10 feet
• D1/16 inch in 12 inches

For large-format tile with any edge longer than 15 inches, the substrate flatness must be no more than:

• A1/4 inch in 10 feet
• B1/8 inch in 10 feet with no more than 1/16 inch in 12 inches
• C3/8 inch in 8 feet
• DWhatever the manufacturer prefers

Industry guidance for framing plumb before float work is that framing should not be out of plumb by more than:

• A1/4 inch in 8 feet
• B1/2 inch in 8 feet
• C1 inch in 8 feet
• DThere is no industry plumb tolerance for framing