Understanding Mortars and Grouts

Once upon a time tile floors were installed and grouted with a single mortar mix. This type of installation required a very highly skilled installer who could work quickly and accurately. The curing time was rather lengthy and involved misting the surface one, two or three times a day for about a week or longer.

Today’s materials are more flexible and do not need long periods of damp curing nor expert tradesmen. The newer adhesive products may cost more but the labor time is significantly reduced. Here’s a run-down of what you can choose from.

Dry-set thinset mortar:
A combination of sand, Portland cement and other additives that help this mix retain water. Dry-set thinset mortar has high compressive strength and a good bond strength for dry- and wet-areas and for tiles that will be submerged. some manufacturers offer a non-sanded version  of dry-set thinset for small tiles (1″ or less).

Modified thinset mortar:
Modified thinset mortar refers to a thinset mortar that has latex added. The latex can be added on-site as a liquid mixed with dry-set thinset powder. Modified thinset can also have the latex added at the factory: this is referred to as polymer-modified thinset and it is mixed on-site with water. There are some high-strength polymer-modified thinset mortars that require a liquid latex be added, in place of the  water, on-site.

Epoxy thinset mortar:
There are two types of epoxy thinset. Ones is a mixture of sand, Portland cement, epoxy resin and epoxy hardener and it is called epoxy-emulsion thinset. The other is made of sand, epoxy resin and epoxy hardener and it is called 100% solids-epoxy. It can be used as both tile adhesive and grout.

Regular Grout:
Regular grout comes sanded and unsanded. Generally, unsanded  grout is used for joints less than 1/8″ wide, while sanded grout is used to fill wider joints. Regular grout is composed primarily of sand and cement with a colorant and other trace ingredients that help retard setup. Regular grout is mixed with water and should be damp cured for 3-4 days. One note of caution: Sanded grout may scratch polished stone tile and while the correct choice for the joint size an epoxy grout would be better suited. If you really want to use a sanded grout it’s best to rest a sample first to see if it scratches.

Modified Grout:
Modified grout is  regular grout  mixed with latex instead of water. Dry polymer modified grout  has several advantages over a regular grout with liquid additive. They weigh less and it is hard to cheat by diluting the liquid latex with too much water. Modified grout has many benefits including more flexural strength, better color retention and limited damp curing requirements. Some modified grouts require no damp curing at all.

Epoxy Grout:
Epoxy grout is a waterless two-part grout made with epoxy resins (Part A) and a hardener (Part B). Epoxy grout is more difficult to apply and can be quite messy during applications. Epoxy grouts are generally used in wet areas such as kitchen and bathrooms because, once cured, they are water-resistant and easy to clean. Epoxy grouts can replace sanded and nonsanded grouts. While epoxy grout is the most expensive, many say the low maintenance and high durability is worth it. Installation tip: They say you can place half of your epoxy grout mix in the freezer to help slow the curing time because, as you know, once it becomes too stiff to work with you have to pitch it.

Lastly, I want to mention a product that is a double-sided adhesive sheet that replaces mortar. You peel and stick the sheet to the wall, add your tile and you are ready to grout. This can cut the time it takes to put up a backsplash in half. It’s best to use the companion seam tape on joints to ensure a tight seal. Caution: read the specifications carefully. Some of these products are only intended for ultra-thin tiles. If you use standard tiles they may fall off the wall leaving you with a mess that requires you to replace your drywall.

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