CTI Movement Joints & Expansion Joints 3

Question 1

Which ANSI standard section contains general requirements for movement joints in tile work, complementing TCNA EJ171?

Accepted Answer

ANSI A108.01

Answer

ANSI A118.7

Answer

ANSI A137.1

Answer

ANSI A108.10

Question 2

Which installation condition most commonly requires movement joints to be spaced closer together than the standard 20–25 foot interior recommendation?

Accepted Answer

Radiant floor heating systems

Answer

Dark-colored tile selections

Answer

Porcelain tile over ceramic substrate

Answer

Recycled-content backer board

Question 3

A CTI inspector finds that a contractor has tiled and grouted directly over an existing movement joint, sealing it shut. How should this be documented?

Accepted Answer

As a deficiency requiring remediation to restore the joint function

Answer

As acceptable if the grout remains uncracked

Answer

As normal practice for thin-bed tile installations

Answer

As acceptable in dry interior applications only

Question 4

Why do diagonal tile layouts typically require movement joints at reduced spacing compared to straight grid layouts?

Accepted Answer

Diagonal patterns create greater shear stress concentration and reduce the effective span between joints

Answer

Diagonal cuts weaken the tile corners, increasing breakage risk

Answer

Diagonal layouts use more adhesive, increasing thermal mass

Answer

Building codes mandate closer joints for any non-90-degree pattern

Question 5

When inspecting a tile installation, which condition at a movement joint would indicate sealant failure requiring remediation?

Accepted Answer

Cohesive or adhesive splitting, cracking, or pull-away from tile edges

Answer

Sealant color slightly lighter than the grout

Answer

Slightly convex sealant surface above the tile plane

Answer

Sealant installed flush with the tile surface

Question 6

A movement joint is specified at 3/8 inch wide. What is the correct backer rod diameter to use before applying sealant?

Accepted Answer

1/2 inch (slightly larger than the joint width)

Answer

1/4 inch (smaller than the joint width)

Answer

3/8 inch (same as the joint width)

Answer

3/4 inch (twice the joint width)

Question 7

Per TCNA EJ171, where are movement joints required in relation to changes in substrate type within a tiled floor?

Accepted Answer

Directly over the transition between different substrates, regardless of thickness difference

Answer

Only if the substrates are more than 2 inches different in thickness

Answer

Only in exterior or wet area applications

Answer

Only when dissimilar metals are used as substrate supports