CTI Movement Joints & Expansion Joints 2

Question 1

What material should be installed inside a movement joint before applying sealant to control joint depth and prevent three-sided adhesion?

Accepted Answer

Polyethylene foam backer rod

Answer

A polyethylene foam backer rod is inserted into the joint to control sealant depth and prevent three-sided adhesion, allowing the sealant to flex properly under movement.

Question 2

For exterior tile installations, what is the maximum recommended spacing between movement joints per TCNA EJ171?

Accepted Answer

8–12 feet in each direction

Answer

Exterior installations are subject to greater thermal cycling, so TCNA EJ171 requires closer movement joint spacing of 8–12 feet in each direction.

Question 3

A CTI inspector observes a 30×30 foot interior tiled floor with no movement joints anywhere. What deficiency does this represent?

Accepted Answer

A code and standards violation with risk of cracking or tile failure

Answer

A 30×30 foot floor without movement joints far exceeds the 20–25 foot maximum spacing required by TCNA EJ171, creating a high risk of tile cracking or delamination.

Question 4

Which material must NEVER be used to fill or close a movement joint in a tile installation?

Accepted Answer

Portland cement grout or mortar

Answer

Portland cement grout and mortar are rigid and will not flex with movement, defeating the purpose of the joint and causing the surrounding tile to crack or debond.

Question 5

What is the purpose of a 'soft joint' (movement joint) installed at changes in plane, such as where a floor meets a wall?

Accepted Answer

To accommodate differential movement between horizontal and vertical tile planes

Answer

Changes in plane experience different movement vectors; a soft joint at the transition allows each plane to move independently without cracking either the tile or the substrate.

CTI - Certified Tile Inspector Practice Test

CTI - Certified Tile Inspector Practice Test

CTI Movement Joints & Expansion Joints 2