CTI Grouting & Finishing Techniques 3 — Questions and Answers
Question 1: According to the Tile Council of North America (TCNA), movement joints (expansion joints) in tile work should be placed:
- Only at the perimeter of the installation
- Wherever the tile field changes direction or at structural joints, plus every 8-12 feet in large fields (Correct answer)
- Only over control joints in the substrate
- Every 4 feet in all directions regardless of substrate
Correct answer: Wherever the tile field changes direction or at structural joints, plus every 8-12 feet in large fields
TCNA guidelines call for movement joints at changes in direction, over structural joints, and within large fields (every 8–12 feet interior, 8–10 feet exterior) to accommodate thermal and structural movement.
Question 2: What is the correct procedure when grout is starting to set up in the bucket before you finish the job?
- Add water to re-temper the grout and continue working
- Discard the batch and mix a fresh, smaller quantity (Correct answer)
- Add more grout powder to stiffen it back up
- Refrigerate the bucket to slow the set
Correct answer: Discard the batch and mix a fresh, smaller quantity
Re-tempering grout by adding water after initial set compromises its strength and bond; the proper solution is to discard and mix a fresh batch.
Question 3: A tile installer notices that grout joints on a newly completed wall installation appear sunken or concave. This most likely indicates:
- The grout was tooled too aggressively with the float
- The grout was not packed sufficiently into the joint depth (Correct answer)
- The grout was mixed too wet
- The tiles were set too deeply into the mortar bed
Correct answer: The grout was not packed sufficiently into the joint depth
Sunken or concave grout joints result from insufficient packing during application, leaving the grout below the tile face rather than flush with it.
Question 4: Which type of grout is most appropriate for a food-preparation countertop installation where stain and chemical resistance are paramount?
- Sanded portland cement grout
- Unsanded latex-modified grout
- Epoxy grout (Correct answer)
- Furan resin grout
Correct answer: Epoxy grout
Epoxy grout is non-porous, highly stain-resistant, and resists most chemicals, making it the preferred choice for food-preparation countertops.
Question 5: During grout cleanup, the tile installer should change the rinse water in the bucket:
- Only when it turns completely opaque
- Frequently to prevent redepositing dissolved grout back onto the tile surface (Correct answer)
- Once per grouting session
- Only after each tile row is cleaned
Correct answer: Frequently to prevent redepositing dissolved grout back onto the tile surface
Dirty rinse water contains dissolved grout solids that will redeposit and harden on tile surfaces as a haze if not changed frequently.
Question 6: What is the recommended minimum cure time before sealing a cementitious grout in a typical interior application?
- 24 hours
- 48 hours
- 72 hours
- 7 days (168 hours) (Correct answer)
Correct answer: 7 days (168 hours)
Most grout sealers require cementitious grout to cure for a minimum of 72 hours, though many manufacturers and industry guidelines recommend waiting 7 days for full cure before sealing.
Question 7: A specifier calls for 'unsanded grout' on a project. At what joint width would you flag this as potentially problematic?
- 1/16 inch
- 3/32 inch
- 1/8 inch
- 3/16 inch (Correct answer)
Correct answer: 3/16 inch
Unsanded grout is recommended for joints up to 1/8 inch; joints at 3/16 inch or wider risk excessive shrinkage and cracking without sand as aggregate filler.
CTI Grouting & Finishing Techniques 3
According to the Tile Council of North America (TCNA), movement joints (expansion joints) in tile work should be placed: