Thinset for Shower Floor: What it Is and Why it Matters

People put a lot of time and thought into choosing the type and design of their shower tile. Design, style, and make are the crucial features that motivate us to renovate and build. Few of us give thinset for shower floors any thought at all.

Thinset is vital for installing tile correctly. In the trade, other names for thinset are mortar, thinset mortar, thinset cement, dryset mortar, and dry bond mortar. Though the names may differ, the compound does one specific thing.

Thinset allows tile or stone to adhere to the surface material below. It’s not the same as grout filling the gap between tiles.

Match Your Thinset to the Type of Tile

If you’ve ever stood in the tile aisle at your local home building store, you’re familiar with the sacks and buckets of tile mortar. 

Thinset is an adhesive bonding material applied over waterproofing membranes, raw cement, cement, or fiber boards. The type of tile material will impact the kind of thinset you choose. 

Deciding factors for thinset:

  • Type of tiling material like ceramic, stone, metal, glass, or porcelain
  • What is below the surface of the thinset like old tile, cement, wood, backer board

Speak with your tile salesperson for the best pairing material for each type of tiling and substrate. What you want from your thinset is a quality adhesive made of fine sand, cement, and cellulose (alkyl derivate) to help retain water.

Additionally, thinset for shower floors may have additives like latex or polymers for optimum adhesiveness.

Correctly installing tile is crucial to prevent leaks and cracking and to create a barrier surface. Home renovation trends are gearing toward larger, oversized tiles. While the look is unique, what goes beneath will help wear and tear and ensure longevity.

Choosing a Thinset

Thinset does a silent but essential job. A quality thinset is easy to use and floats across the surface to diminish uneven spaces between the tile and substrate. A substrate is a fancy way of saying the surface below.

A quality thinset holds the tile in place and allows the tiler to complete the task before the compound cures or hardens. Tiling and spreading thinset takes practice, the right tools, and planning.

Thinsets have evolved too. They’re easy to use in the right environment with suitable materials.

A good thinset application:

  • Creates a perfect seal between tile and substrate
  • Mixes and applies smoothly and easily
  • Repels moisture to eliminate mold growth
  • Fills in air pockets
  • Depends on where the tile is installed (high traffic)

A poorly installed thinset application:

  • Leads to cracked tiles 
  • Causes leaking
  • Quicker wear & tear on tile
  • Looks bad and makes a hollow sound

Thinset is a common and versatile mortar for bonding indoor and outdoor tiles. When mixed according to manufacturer instructions, thinset has a smooth, pliable texture. Standard ingredients include Portland cement, silica sand, and additional water-retaining ingredients unique to each brand.

Standard Thinset

Many building sites use this version of thinset. It’s readily available from your local store. Standard thinset requires mixing with water. It’s crucial to mix smaller batches that match your tile-setting skills.

Premixed Thinset

Premixed thinset is an upgrade from standard thinset because it remains pliable in its bucket format. Since it’s premixed, it’s also easier to use for building sites with limited water resources. The downside is that premix is heavy and costly. However, it is more user-friendly for professionals and beginners.

Either choice will create the bonding material for your tile project. Premixed is cost inhibitive for large-scale tile jobs.

Applying Thinset Mortar

One of the key elements of using thinset mortar is planning ahead. Before you mix a powered thinset, arrange your trowel, spacers, and accessory tools nearby. Make sure you have a pattern tile laid out that you can easily follow.

Thinset is a flexible material that won’t shrink once it’s set. Its heat resistant and prevents mold growth. Skimping on thinset creates air pockets that will crack your tiles. Thinset is a perfect mixture for wet environments like showers, wetrooms, laundry, tub surrounds, and outdoors. 

Thinset can compensate for slightly uneven surface differentials but can’t fix highly uneven floors. To help high-traffic tile areas compensate for constant use, add a latex additive to increase the thinset’s durability.

Applying Epoxy Mortar

Epoxy tile mortar is another excellent tile mortar thinset that works well with damp surfaces and resin-backed stone materials to create a strong bond. One of the key features is its compressive strength which is excellent for higher-grade tiles.

Epoxy is usually two or three-part material that needs to be mixed right before use. Since it’s impervious to water, it doesn’t require additional latex ingredients to make it flexible. Epoxy is temperature sensitive and sets very quickly.

Professionals prefer epoxy tile mortar when installing ceramic or porcelain tile. It’s also versatile for use with glass, rock, stone, metal wood block floors, and rubber floors. It has a powerful odor, and proper ventilation is vital.

One of the key benefits of epoxy is that it cures faster and allows tilers to complete tiling jobs quicker. It sets in a few hours but costs more.

Epoxy tile mortars have many benefits and are chemical resistant, and will not stain the expensive ceramic tiles. A key caveat is that they require warm temperatures between 60- to 90F. It’s crucial to remember that new concrete requires 28 days of curing before using any thinset or epoxy.

Preventing Thinset Adhesion Problems 

Tiling is a skill. It takes planning and a ton of time on your knees. Before investing valuable resources on tiles, make sure you follow manufacturers’ guidelines. They’ve tested the product.

Here are our tips to make sure you start on the right footing.

1. Substrate

Install tile only on the correct substrate. Thinset works with cement board set on ¾” graded plywood. If any components are wrong or inferior, you’ll end up with cracked tiles.

2. Tile Grades

Not every type of tile works on the floor—manufacturers rate tiles into several categories. Floor tiles are usually a grade 1 or 2, while walls are a grade 3. Grade 3 tiles are thinner and can’t bear the weight of foot or appliance traffic. See PEI scale.

3. The Wrong Thinset

Don’t skim out on the thinset. No one will see it; that’s true. But if you don’t buy a quality thinset or a tile manufacturer-recommended thinset, you’ll weaken your tile project’s durability.

Using too little thinset will also produce a poor tiling job. Make sure the thinset application matches the recommended notch mark in the trowel. Apply tile to wet thinset.

4. Underestimating Wall & Floor Movement

Temperatures cause walls and floors to flex. If you install your tile too close to the wall without allowing joint room, your wall and floor might eventually heave. It will cause a split in the center of the floor.

5. Foundation

New builds can suffer from settlement problems if the grading below ground below is shoddy. Make sure your groundwork is solid and not prone to shrink or expand.

6. Inadequate Preparation

If you’re tiling over joined cement boards, make sure you tape the seams with the proper fiberglass mesh tape. Also, spread thinset over nail or screw indents.

7. Wrong Floor

When tiling flooring, consider the joist span beneath. Tile adds additional weight. If your joists’ spacing is more than 16” apart (center), you end up with spongy and flexible floors that will cause cracking.

8. Curing Time

Thinset of any type needs time to cure. Epoxy cures faster, but the average time before walking on tile is from 48 to 72 hours. 

Final Thoughts

Spending money on thinset for shower floor is more important than you might have realized. Replacing tile that wore out before its time is costly, messy, and time-consuming. Doing the job like a professional in the first place saves those headaches.

Thinset isn’t expensive and should match your tile choice and substrate.

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