Specifying the right grout for the project

by Katie Daniel | July 14, 2015 2:14 pm

[1]

By Steve Taylor
The vast array of tile materials and grout colours makes tile design an exciting element of construction projects. However, this can also mean the grout type is relegated to an afterthought, instead of being planned as an integral part of the installation system.

Primarily, grout choice should be driven by the needs of a tile assembly, which is based on environment and usage. Some considerations for design professionals include:

• determining whether the tile and grout will be exposed to moisture and temperature fluctuations;
• potential damage from acidic materials and cleaning regimens; and
• owner expectations toward grout maintenance.

The demands that will be made of the tile will also affect the grout and how it will hold up as a part of the installation.

Choosing the right colour to match or contrast with the tile is only a secondary consideration once the critical specification of grout type has been made. Owners expect a tile assembly to be hard and durable, esthetically pleasing, and stain-resistant—and this includes the grout. These goals can be achieved by specifying the exact type of grout used in the installation in addition to the colour.

With advances in grout technology, there are many factors to consider when selecting the right grout. This article helps to explain the different types and how to choose the appropriate grout for specific projects. The Tile Council of North America (TCNA) and the Terrazzo, Tile, and Marble Association of Canada (TTMAC) define six types of grout based on the chemical composition and performance of each. The expected use of the tile assembly should ultimately determine which one must be specified.

Grout types
Standard cement grout is a general purpose grout traditionally used in various installation types. It is defined in the TCNA Handbook as a factory-prepared mixture of cement, fine aggregate, and other ingredients to produce a water-resistant, dense, uniformly-coloured material for joints that are 3.2 mm (1⁄8 in.) or less. The fine aggregate is generally replaced with clean, graded sand for joints greater than 3.2 mm. The coarser grout for larger joints is labelled as sanded grout and the finer-grade material suitable for joints less than 3.2 mm is referred to as non-sanded grout. Non-sanded is also preferred for highly polished tile or soft stone tiles easily scratched by sand. The performance of this type of grout is defined in American Nation Standards Institute (ANSI) in A118.6, Standard Cement Grouts for Tile Installations. Standard cement grout can be specified for interior, exterior, wet, dry, and even submerged applications.

Today, most of these grouts incorporate polymers to reduce water absorption and increase flexibility. The addition of polymer also reduces efflorescence and grout cracking. Since this grout is porous, it should be sealed regularly with a penetrating sealer to improve the stain resistance and durability. Typically, this general purpose grout has the lowest cost per pound.

High-performance cement grout should be specified wherever higher bond and flexural strength is desired or reduced water absorption is needed. This category of grout is defined by TCNA as a factory prepared mixture of cement and other ingredients, including a re-dispersible latex/polymer powder (to which water is added at the jobsite) or a liquid latex admixture (added at the jobsite in place of the water) designed for grout joints 3.2 mm (1⁄8 in.) or less. Generally clean, graded sand is added for grout joints greater than 3.2 mm. High-performance cement grout is defined by ANSI A118.7, Polymer-modified Tile Grouts for Tile Installations. In some installations, regular standard cement grout fails because it does not dry hard (compared to the tile surface). It can mottle or shade in the joints and cure with efflorescence on the grout’s surface.

[2]

High-performance cement grouts were developed with improved curing technology and advanced polymers to minimize these issues. These products use unique cements, polymers, and modifiers that help complete the hydration process in a short time to develop hard, dense, and uniformly coloured grout joints. While specifying high-performance cement grout will eliminate many of the concerns of traditional cement-based grout, it is still porous and must be regularly sealed with a penetrating sealer to prevent staining by common household materials. High-performance cement grout is approximately twice the cost of its standard counterpart.

Since all cement-based grout is sensitive to acidic chemicals, they do not hold up well in environments exposed to strong chemicals or rigorous cleaning schedules. Developed to provide the required chemical resistance in demanding installations is 100 per cent solids epoxy grout. The TCNA Handbook defines epoxy grout as a grouting system employing epoxy resin and hardener portions, often containing coarse silica filler. These are formulated for industrial and commercial installations where chemical resistance is important.

The performance of epoxy grout is defined in ANSI A118.3, Chemical Resistant, Water Cleanable Tile-setting and Grouting Epoxy and Water Cleanable Tile-setting Epoxy Adhesive. These two- and three-component grouts are composed of water-cleanable epoxy resins, special hardeners (curing agents) and clean, graded aggregates. They do not contain volatile solvents or water and are considered 100 per cent solids. The epoxy resin binder in these grouts has more chemical resistance (primarily to acidic materials) than the more common cement grouts. Due to their ability to resist chemicals, epoxy grouts are commonly used in commercial applications routinely exposed to corrosive chemicals or foods for extended periods, such as commercial kitchens, dairies, and beverage bottlers.

[3]

Since epoxy grouts eliminate many of the issues experienced with cement grouts and have stain-resistant properties, they have also found use in some non-commercial tile installations like residential kitchens and baths. Many installers remember when epoxy grouts were hard to spread and clean up. There have been considerable improvements to the formula and today’s epoxy grout is easy to use. While these grouts solve nearly all the concerns of cement-based grouts, they are expensive and can run 10 times the cost of a standard cement grout.

According to the TCNA Handbook, epoxy emulsion grout is a grout system employing epoxy resin and hardener portions, both of which contain additional water to form an emulsion. The coarse sand filler portion also contains portland cement and this grout meets the performance of ANSI A118.8, Modified Epoxy Emulsion Mortar/Grout. Epoxy emulsion grouts are a hybrid of the 100 per cent epoxy grout and the portland cement grout. Generally, they cost less than a 100 per cent epoxy grout because they are extended with water. These grouts rely on the hydration of the portland cement in addition to the cured epoxy resin for their ultimate strength. However, because performance depends on the hydration of the portland cement, they can be prone to the same issues plaguing standard cement grouts. They are still somewhat porous and can be stained when exposed to common household materials. At one time, these were preferred for bonding ceramic tile to plywood, but with the development of polymer-modified cement mortars, they are rarely used for this purpose and are not readily available. Today, few epoxy emulsion grouts can be found on the market, as they have been replaced with easier-to-use 100 per cent solids epoxy grout, higher-performance cement grout, and recently developed premixed grout.

[4]

TCNA defines furan resin grout as a grout system consisting of furan resin and hardener portions. It is specialized and used in industrial and commercial installations that may require chemical resistance. Furan is a thermosetting polymer that can withstand continuous exposure to temperatures up to 176 C (350 F). As a grout, it is primarily used in applications such as dairies, that require resistance to routine exposure to organic acids (contained in milk products) and elevated temperatures. Furan is a reactive polymer-like epoxy. These grouts require special installation techniques and should not be attempted by a novice. They cannot be cleaned from the surface of the tile with water alone during the installation process. The performance of furan grout is defined in ANSI A118.5, Chemical-resistant Furan Mortars and Grouts for Tile Installation.

While furan is not widely used, many tile installation product manufacturers have developed improved epoxy grouts meeting the performance requirements of ANSI A118.5. These epoxy grouts have improved chemical resistance and will hold up when exposed to high temperatures. They are ideal for use in commercial kitchens routinely cleaned with steam and harsh chemical cleaning agents, including the no-rinse enzymatic cleaners.

The most recent addition to the grout selection in the TCNA Handbook is premixed polymer resin grout and is defined as a one-part liquid ready-to-use grout requiring no mixing with water. These easy-to-use grouts are generally a mixture of polymer (acrylic, silicone, or urethane), fine fillers, and water. They are pre-blended at the factory and can be applied to the joints between the installed tiles straight from the container; no mixing is required. While these premixed grouts are recognized by TCNA and the tile industry, they do not have an ANSI specification at this time and performance can vary from manufacturer to manufacturer. However, the pre-mixed or single component grouts have been specifically formulated to eliminate the issues seen with traditional cement and epoxy grouts. When fully dried, they can be hard, uniformly coloured, and completely stain resistant.

Installers also benefit from not having to use a full container of product. At the end of the day, they reseal the lid for the next day or the next job. Traditional cement and epoxy will harden in the mixing container and need to be disposed of the next day. This also reduces waste in the field. Premixed grouts are easy to spread and will completely fill the joints between the tiles. The grout can be used in most applications where a cement or epoxy grout is used. While premixed grout may be twice the cost of a high-performance cement grout, it is much less than an epoxy grout, and may not require the use of a grout sealer.

[5]

Caulking movement joints
While caulks and sealant are not classified as a grout, they do fill the movement joints between tiles in a correctly installed tile assembly. They are defined in the TCNA Handbook as suitable sealants/caulks that include silicone-, urethane-, and polysulfide-based materials. The sealant/caulk must meet the requirements of ASTM C-920, Standard Specification for Elastomeric Joint Sealants:

• Type S (single-component) or M (multi-component);
• Grade P (pourable) or NS (non-slump);
• Class 25 or 12.5 (i.e. allowable per cent movement); and
• Use T (traffic) or NT (non-traffic), M (use on mortar), and G (use on grout).

Sealant/caulk for use in traffic areas requires a shore hardness of 35 or greater.

The tile installation is not complete until the soft movement joints are properly installed. There is movement in every floor and wall, which can be caused by curing of cement/concrete surface, thermal changes, or even settling of the structure. Wherever movement is suspected, an elastomeric sealant or caulk should be installed in place of the rigid grouts previously described.

[6]

Placement of movement joints in the tile assembly is described in ANSI and the TCNA Handbook. They should be placed every 6 to 7.6 m (20 to 25 ft) in interior spaces and every 2.4 to 3.6 m (8 to 12 ft) in exterior installations and areas exposed to direct sunlight. Soft joints should also be installed wherever there is a change of plane or independent movement of two surfaces is suspected. With some of the large-format tiles, up to 1.5 x 3 m  (5 x 10 ft), it is best to fill all the joints around the tile with the elastomeric sealant to meet the industry recommendations. Caulk and sealant are formulated in nearly every colour to match the hard cement and epoxy grouts available.

Conclusion
Selecting the right grout may seem daunting with so many choices, but proper selection will ensure the tile assembly’s longevity. In the past, cost was a major consideration in product selection and using a specialty grout that was several times more expensive was out of the question. Now, an increasing amount of large-format tiles are specified, and the amount of grout required for the job has been significantly reduced.

For instance, to tile 93 m² (1000 sf) with 203 x 203 mm (8 x 8 in.) tile and a 6.35-mm (¼-in.) joint spacing requires about 90 kg (200 lb) of cement grout. If the tile size is increased to 609 x 609 mm (24 x 24 in.), the project only needs 34 kg (75 lb) to fill the joints in 93 m² (1000 sf). With the market trend toward larger tiles, the cost of the grout becomes less important. This makes it easier to justify an appropriate grout that provides uniform appearance, consistent colour, crack resistance, and stain-proofing at a higher price.

When specifying tile on a project, one should go beyond colour and analyze how the installation is going to be used. Designers and project teams want the artistic quality of the installation to be visible for years to come, so it is important to select materials that stand the test of time. For demanding installations, a high-performance epoxy grout or one of the newer premixed or ready-to-use grouts should be considered, rather than a lower-cost traditional grout.

The same grout should not be repeated out of convenience, unless this installation is identical to the last. Every installation has its own unique needs and deserves a full evaluation. Many grout manufacturers have professionals on staff that understand the different grout types and can help with the best selection for any tile project.

[7]Steve Taylor is director of architecture and technical marketing for Custom Building Products. With more than 30 years of experience developing products for the construction industry, he is on the board of the Tile Council of North America (TCNA), a member of Material and Methods Standards Association (MMSA), and American National Standards Institute (ANSI). In these roles, Taylor helps to determine proper tile installation methods and product standards. He can be contacted at stevet@cbpmail.net[8].

Source URL: https://www.constructioncanada.net/specifying-the-right-grout-for-the-project/

---