There are a lot of steps involved to properly installing tile in a shower. This is especially true today, when a mixture of tiles including natural stone, glass, mosaics, pebble tiles and large-format porcelain are commonly used together in the same space. Of course, showers must also be waterproofed to protect the building and its occupants. In addition, ceramic tile and stone contractors are constantly pressured to meet tight schedules—while at the same time delivering a fabulous-looking result.
What is the best way to overcome these challenges for a successful shower installation every time? There are several key installation steps:
- Select a method for forming the shower pan floor. Take into consideration the finished tile elevations at the walls and drain, then create a proper pitch ≥1/4” per foot at the tile surface as well as under the waterproofing membrane.
- Create an absolutely watertight shower pan and ensure that all walls, benches and niches are waterproofed to protect adjoining areas.
- Bond the tile or stone with ≥95% mortar coverage without excessive lippage.
- Grout properly and install a flexible sealant in movement joints.
For the traditional shower pan method using a mortar bed and waterproofing membrane, there are multiple methods accepted by the Tile Council of North America (TCNA). In TCNA Detail B415, a pre-slope of mortar is placed first to create a pitch for the waterproofing membrane or liner. When this mortar dries, the membrane is applied to the pre-slope. Afterwards, the mortar bed is placed and allowed to dry.
In TCNA Detail B421, the mortar bed is placed on the substrate, with a radius around the drain left open in order to tie the waterproofing membrane into the drain collar. When the mortar bed dries, the waterproofing membrane is applied over it and the radius is filled in. In both cases, pea gravel is placed around the drain collar in order to allow water to flow through weep holes.
Based on temperature, humidity and cure rate of the product used, the mortar bed may have to cure for 72 hours prior to installation of the waterproofing membrane. After the membrane is applied, another 24 hours may be required prior to flood testing. Check with the installation material manufacturers for rapid-setting/curing mortars and waterproofing to accelerate the installation schedule.
Choose the right waterproofing for the project based on the available options:
Pros: Seamless and easy to apply, similar to painting; conforms well to changes of plane, curbs, niches, walls and ceilings; some are rapid-setting for flood testing and tiling within hours.
Cons: Installer is required to ensure monolithic coverage, minimum thickness and sufficient dry times.
Vinyl Sheets (Chloraloy)
Pros: Typically applied by licensed plumber; immediately ready for installation.
Cons: Plumbers often neglect a pre-slope, creating drainage issues in mortar bed; may need to shim out walls to accommodate vinyl thickness and folds in corners and above curb.
Adhered Sheet Membranes
Pros: Sheet is waterproof and once seam adhesive cures, it’s ready to flood test or tile.
Cons: Sheets have to be cut and fitted to size around changes of plane, curbs and niches—similar to wallpapering; seams need to be treated properly to prevent leakage.
Once the waterproofing is ready, install the tile or stone with the correct mortar. Technology has really advanced with options for high performance bond strength and deformability that is required for glass and porcelain tiles (ANSI A118.15 Improved Modified Dry-Set Cement Mortar). Many of these mortars are thixotropic and can hold very heavy tiles (more than 10 lbs./sq. ft.) firmly in place without sagging on walls and ceilings.
Natural stone tiles should always be set with white mortar to help prevent darkening. Before choosing a natural stone for a shower, confirm with the supplier that it is suitable for a wet area. Some stones have minerals that could permanently discolor or emit a rust effect.
Natural stone suppliers may recommend six-sided application of a penetrating sealer to mitigate these issues. Porous stones such as limestone may take a very long time to dispel moisture from the mortar, so rapid-setting mortars are recommended. When stone is set on a shower floor, pay particular attention to how gravel is placed at the weep holes around the drain, otherwise prolonged moisture and soap scum can cause degradation or discoloration.
To achieve required mortar coverage of 95% in wet areas, proper trowel sizes, directional combing and back-buttering of large-format tile and stone are essential steps. For valuable insight on these methods watch the National Tile Contractors Association (NTCA) “Trowel & Error” video, available on YouTube in both English and Spanish.
Choosing a grout
Completely fill joints with a suitable grout for the tile and conditions, and install sealant in movement joints in changes of plane and where required. Grout types and methods of installation are defined by the American National Standards Institute (ANSI). Product characteristics and minimum performance levels are listed in the A118 section; methods of installation in A108.
The grout joint is to be finished consistently, packing the grout firmly and to a maximum fill as much as is reasonably possible. This locks the tile in place and helps shed surface water to the drain. Cement-based grouts can be sealed to improve stain resistance. Sealant or caulk is to be placed at all changes of plane instead of grout. The joint below must also be free of mortar in order for the assembly to expand and contract due to expansion from heat and moisture.
Grout and sealant options include:
Standard Cement Grout, Sanded/Non-sanded (A118.6)
Pros: Low price; readily available; wide variety of colors. Non-sanded can be used for soft or polished tile that may otherwise scratch.
Cons: Color and hardness more easily affected by temperature, tile porosity and installer error.
High-Performance Cement Grout (A118.7)
Pros: Stronger physical characteristics; lower porosity; more color consistent due to curing process; reduces efflorescence.
Cons: Often rapid-curing and relies on installer prowess to finish in appropriate timeframe.
Epoxy Grout (A118.3)
Pros: Impervious as a porcelain tile so highly resistant to soaps, cleaners and staining.
Cons: Requires attention to instructions to prevent haze and intensive cleanup.
Single-Component/Pre-mixed (No Standard)
Pros: Color-consistent; stain-resistant; reduces errors in mixing process.
Cons: Slightly longer cure time before water exposure.
Latex Acrylic Caulk
Pros: Easy to apply; low cost; color-matched to grout.
Cons: Not recommended for floor-wall intersection; more susceptible to staining.
100% Silicone Sealant
Pros: Long-lasting (some to 50 years); resists staining and performs well even on horizontal surfaces.
Cons: More difficult to apply and finish than caulk.
Although there are many choices and challenges in shower applications, professional tile installers—especially those with industry recognized training—are up to the task. Recognized tile and stone installation certifications include National Tile Contractors Association (NTCA) Five Star Contractors, Tile Contractors Association of America (TCAA) Trowel of Excellence Contractors, International Masonry Institute (IMI) Foreman Certification, and Ceramic Tile Education Foundation (CTEF) Certified Tile Installers as well as those recognized by the U.S. Department of Labor as Journeyman Tile Layers.
Installation material manufacturers supply compatible products for the entire system and when single-sourced, may provide up to a lifetime system warranty. Using integrated systems—including the mortar bed, waterproofing, thin-set mortar and grout—can create a long-lasting installation and meet project schedules.