Treating Static vs Dynamic Joints


The difference between static & dynamic joints

Static cracks and control joints are non-moving parts, which makes them easier to work with during installation. Dynamic cracks and expansion joints, however, are moving parts and need much more attention. Let’s take a look at some of the differences between static joints and dynamic joints.

Start with thorough preparation

Of course, all substrates must be structurally sound and free from any contaminants that may inhibit bond, including oil, grease, dust, paint, sealers, floor finishes, curing compounds, adhesives, etc. For the specific treatment of joints, follow the appropriate industry standards and the flooring manufacturer’s recommendations. The first step, regardless of whether it’s a static or dynamic joint, is to remove any dirt, debris or existing sealant. 

Apply the penetrating moisture vapor barrier

Once the cracks or joints have been thoroughly cleaned, apply TEC® LiquiDAM™, a penetrating moisture vapor barrier. Spread the blue mixture into the joint with a paint brush to completely coat the walls of the cavity. LiquiDAM works with all types of static and dynamic joints and cracks

For static cracks and control joints greater than 1mm, you’ll need LiquiDAM along with silica sand and a small bucket. Blend in a one-to-one ratio of LiquiDAM and silica sand into the bucket and mix. Larger cracks may require a different ratio, so check the manufacturer’s data sheet for the proper ratio. Immediately pour the blend into the coated control joints and cracks, then level it out with the concrete surface. 

Be especially aware of dynamic joints

Expansion joints and dynamic cracks are treated differently. After coating the cavity with LiquiDAM, allow it to cure. Then, fill the joints with sand or a backer rod while leaving the top of the joint open for proper treatment with a sealant. 

Remember that expansion joints are going to move since they’re designed to expand and contract with the concrete. You cannot pour a self-leveling underlayment directly over one. You also can’t tile, cement or apply patch directly over an expansion joint because sooner or later that crack will go through to the surface. Basically, you can’t put any product directly over the expansion joints.  


This is an example of what can happen when you don’t honor the movement joints.


Once you’ve treated the dynamic joint with LiquiDAM, you’ll need to add the same soft joint throughout the entire installation. You can either line up the grout joint lines or cut the tile to fit the expansion joint through the entire tile installation. However you choose to do it, dynamic and expansion joints demand your attention to avoid future problems.

Crack isolation membrane over saw cut and static joints

One other option to consider for static and saw cut joints is to apply a crack isolation membrane, HydraFlex™. Without this membrane, any tile installed over saw-cut joints is normally at risk because eventually it will lead to a crack. HydraFlex provides assurance and flexibility for architects, contractors and customers to be less concerned that saw cut joints or static cracks will transfer through the tile. 

Need some technical advice or product information? Contact our Technical Services Team for answers. You can also call 1-800-832-9023, Mon-Fri 7 a.m. - 6 p.m. CST.

Posted by
TEC Staff