Thursday, July 21, 2011

Technical Advisory - Movement Joints

This Technical Advisory deals with the TCNA 2011 handbook methods for Movement Joints

This Technical Advisory deals with one of the most important topics in our industry – Movement Joints.
EJ171 Movement Joint Guidelines for Ceramic, Glass and Stone – pages 271 – 275
The same 10 movement joint details carryover from the 2009 TCNA Handbook, however, the narrative has changed.
A discussion of the importance of movement joints now appears in the section.
Some critical changes are as follows:
1. Above ground concrete slab structures now require movement joints placed every 8’ to 12’ (2.4-3.6m) in each direction.
2. A caution is provided concerning the use of crack isolation membranes and relocating movement joints. Typically saw cut / control joints and cold joints can be relocated when utilizing a crack isolation membrane. The tile contractor is not held responsible for cracking when movement joints are relocated. The crack isolation manufacturer must provide clear direction when movement joints are relocated. The LATICRETE guidelines on this issue are to treat saw cut joints with our crack isolation membranes covering the movement joints a minimum of three times the width of the tile / stone finish and then to install a flexible sealant in the joint closest to the movement joint. Consult the individual product data sheet for more information as the type each membrane type may have some unique installation methods associated with it (e.g. fabric reinforced membranes versus non-fabric reinforced membrane types). We basically treat cold, saw-cut control and non-structural shrinkage cracks in accord with F-125 and F-125A by locating a soft, sealant filled joint at the next available joint.
3. A caution is provided concerning the installation of “saw-tooth” movement joints used to relocate movement joints for tile patterns that fall diagonally across movement joints. The preferred treatment is to place the movement joint where it falls. Sealant performance diminishes when installed in a saw tooth pattern.
4. A caution is provided concerning the potential staining of natural stones when using silicone sealants.
Expanded definitions of the various joint types (with a corresponding detail) are now included in this section:
Construction / cold joint
Contraction / control joint
Expansion joint
Isolation joint
Movement joints have been the subject of much debate as they pertain to the installation of adhered concrete masonry veneer (ACMV). Many ACMV manufacturers are silent on the inclusion and / or placement of movement joints. Laticrete Technical Services has recommended the exterior movement joint guidelines of the TCNA in the absence of project specific designed movement joints. However, at times ACMV manufactures have stated that the TCNA guidelines may be too conservative for their finishes. Therefore, in some instances, the Brick Institute of America (BIA) placement of movement joints has been prescribed (e.g. every 20 to 25 ft [6-7.5m] vertically spaced and at every floor [~ 10’ – 12’ (3-3.6m)] horizontally. Therefore, movement joints must be placed at corresponding joints in the substrate and in accord with either the Design Professional’s or ACMV manufacturer’s prescriptive guidelines.
Natural stone veneers fall under the guidelines of the TCNA manual for movement joints.
Let me know if you have questions or concerns.
Arthur Mintie
Technical Services Director
LATICRETE International
Tel. +1.203.393.0010 ext. 326

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