Tile Flooring Basics: Porcelain, Ceramic, Stone and What Goes Under It

Tile is one of the longest-lasting floors you can install. It's hard, waterproof when properly installed, easy to clean and available in endless looks, including convincing wood-look planks. It's also the least forgiving of flooring materials when it comes to the structure underneath. Tile doesn't flex, so if the floor below moves, the tile or grout cracks.

Porcelain, ceramic and stone

Porcelain

Porcelain tile is made from fine clay fired at high temperatures, making it dense with very low water absorption. It's very durable and suitable for floors throughout the home, including entries and bathrooms. Through-body porcelain carries color all the way through, so chips are less visible.

Ceramic

Ceramic tile is softer and more absorbent than porcelain, and typically easier to cut. Many ceramic tiles are rated for floors, but some are for walls only. Check the product's rating.

Natural stone

Marble, travertine, slate and granite are beautiful and unique. They require sealing, can etch or scratch depending on the stone, and need stiffer floors than ceramic or porcelain.

Deflection: why the floor's stiffness matters

Deflection is how much a floor bends under load. Industry guidelines from the Tile Council of North America (TCNA) are commonly summarized as L/360 for ceramic and porcelain and L/720 for natural stone, where L is the joist span. A floor that's fine for carpet or LVP may be too bouncy for tile. Joist size, spacing and span, plus the thickness of the subfloor, all matter. Larger tiles, especially large-format tiles, also need flatter floors.

What goes under tile

Tile isn't installed directly on plywood in most cases. Common underlayments include:

• Cement backer board, screwed and set in thinset over the subfloor.
• Uncoupling membranes, thin plastic membranes that help isolate tile from minor movement.
• Mortar beds over appropriate subfloors, a traditional method.
• Directly over concrete, when the slab is sound, flat and has no moving cracks; crack isolation membranes can help over minor cracks.

Each system has a specific installation method, so follow the manufacturer's instructions.

Thinset and coverage

Tile is set in thinset mortar with a notched trowel. Good coverage, meaning the mortar contacts most of the back of the tile, is essential, especially in wet areas and with large tiles. Pros "back butter" large tiles and check coverage by lifting a tile occasionally. Hollow spots under tile lead to cracks.

Layout

Good layout makes tile look professional:

• Start from the center of the room or a focal point so cut tiles at the edges are balanced.
• Avoid thin slivers at doorways and visible walls.
• Plan around toilets, cabinets and transitions.
• For wood-look plank tile, use offsets the manufacturer recommends; long planks often need a smaller offset to avoid lippage (uneven edges).

Grout

Grout fills the joints between tiles. Cement grouts come sanded or unsanded depending on joint width. Epoxy and other high-performance grouts offer better stain resistance. Narrow joints look sleek but need flatter tile and floors. Cement grouts may need sealing; follow the product instructions.

Heated floors

Electric radiant floor heating mats or cables can be installed under tile, a popular upgrade in Wisconsin bathrooms and basements. They need a dedicated circuit and a thermostat installed by an electrician, and they go into the thinset layer according to the system's instructions.

Tile vs LVP

Maintenance

Sweep or vacuum grit often and clean with a pH-neutral cleaner. Keep extra tiles from the same production lot for repairs. Reseal natural stone and cement grout as recommended.