241A Tilesetter Practice Quiz
Free · 174 Questions.

• A full-facepiece respirator or a powered air-purifying respirator with 100-series filters (assigned protection factor 50)
• A half-mask respirator with 100-series filters (assigned protection factor 10), which suits any power-tool dust
• A disposable paper dust mask, since concrete dust calls for the nuisance-dust level of protection
• A supplied-air hood of the kind used for abrasive blasting (assigned protection factor of 1000 or more)

Why: Using a power tool to cut, grind or polish concrete, masonry or terrazzo is Type 2 silica work, which needs a respirator with an assigned protection factor of 50: full-facepiece or powered air-purifying with 100-series filters. A half-mask (APF 10) is the Type 1 level and a supplied-air hood is for Type 3 abrasive blasting.

• L/360 is the general limit for tile, but stone needs the stricter L/720, so this floor is too flexible
• L/360 is the limit for stone, while tile needs the stricter L/720, so the floor suits marble
• L/360 is acceptable for any tile or stone, since the limit depends on the joist spacing
• L/360 is acceptable for marble when the tile is set over a membrane that absorbs the movement

Why: The TTMAC guide gives L/360 as the general maximum deflection for tile and L/720 for natural stone. A floor built to L/360 is too flexible for marble, and a membrane does not cure deflection.

• The room is out of square, since a true rectangle has equal diagonals
• The room is square, since both diagonals are within 20 mm of 5,000 mm
• The room is square, since 3,000 and 4,000 mm give a 5,000 mm diagonal
• The walls are out of level, so the floor elevations must be rechecked

Why: A 3-4-5 rectangle of 3,000 x 4,000 mm has two 5,000 mm diagonals. Unequal diagonals (an 18 mm difference) mean the area is not square, so the layout must be adapted. Diagonals test squareness, not level.

• At least 95 percent contact, back buttering the tile where needed
• At least 80 percent contact, the same as for interior dry floors
• At least 60 percent contact, with the corners left empty to vent moisture
• At least 50 percent contact, concentrated under the tile corners

Why: TTMAC calls for a minimum 95% contact on exterior installations and in wet areas, with 80% accepted for interior dry installations. Back buttering is the usual way to reach the higher figure.

• Forced into the joints with a rubber float, packed free of voids and gaps
• Brushed over the surface with a stiff broom and lightly compacted afterward
• Troweled in with a steel trowel and finished flush using a damp sponge
• Poured on as a thin slurry and left to flow into the joints on its own

Why: The guide specification forces grout into the joints with a rubber grout float so every joint is well compacted and free of voids and gaps. Excess grout is then removed and the tile polished with clean cloths.