Well and properly placed concrete has joints placed throughout the slab to allow different sections of concrete to move due to stress, like temperature changes and drying shrinkage, so that cracks don’t form. The two most common types of joints in decorative concrete are contraction (or “control”) joints and isolation joints. Contraction joints are found in the interior, main body of the concrete and are usually ⅛” or 3/16” wide, and 1” to 1.5” deep. Isolation joints are usually located around the perimeter of the concrete (and near posts or columns) and are usually about ¾” wide and extend through to the sub-grade.
Contraction joints are saw-cut by the concrete contractor just after the concrete is poured, and they are left empty, while isolation joints are formed before the pour and filled with a temporary or inexpensive material. Both joints present potential problems for a decorative concrete floor in terms of maintenance, moisture intrusion, chipping and spalling, durability, longevity and overall appearance, if they are not filled and with a quality, lasting material. Contraction and isolation joints can also present problems, and make matters worse, especially in appearance, if they are filled with the wrong material or not properly cleaned and prepped beforehand.
The decision on whether and how to permanently fill isolation and control fill joints most significantly depends on whether the concrete is indoors or outside, and whether it is in a commercial or industrial setting versus residential. It may also depend on a customer’s personal preferences and budget. Filling joints in a decorative concrete floor with a colored material that complements, matches or accents the main color of the floor is a way to enhance and embellish a great looking floor. This can be important if the project space is in an upscale location or setting, or is an area of a building that has a lot of activity.
There types of materials are used for filling joints in a decorative concrete floor: 1) standard tile grout; 2) elastomeric urethane joint sealant; and 3) semi-rigid epoxy or polyurea joint filler. Most contractors, if they offer this service, will use colored tile grout because it’s the simplest method. But grout is difficult to clean, and it cracks and comes loose over time. Premier Veneers uses colored, high quality urethane joint sealant from Sika and polyurea joint filler from Metzger/McGuire to fill isolation and contraction joints, because these products look much better, are dirt- and stain-resistant, and last indefinitely. We also use these materials to fill saw-cuts we may make in a floor during the course of a project for design purposes (see "Decorative Scoring").
Premier Veneers is trained and certified in joint filling, and we make recommendations at the outset of every acid-stained or decorative concrete flooring project about whether to fill joints and with what type and color of material.