Grout for Kitchen Tile: Cement, Epoxy and Urethane, Plus Joint Width and Colour

Grout is a small share of a tile job and a large share of how it ages. It is the part that stains, the part that cracks when something moves, and the part that decides whether a wall of tile reads as one surface or as a grid. Choosing it takes four decisions: the type, the joint width, the color, and where grout should not be used at all.

Grout types compared

The tile industry sorts grout by American National Standards maintained through the Tile Council of North America (TCNA). The standard a product meets is printed on its data sheet, and it tells you more than the name on the bag.

Cement grouts

Cement grout is Portland cement, pigment and (in sanded versions) fine aggregate, mixed with water on site. It has been the default for generations and is easy to repair. Its weakness in a kitchen is porosity. Cooking oil, coffee and red sauce soak in unless the joints are sealed, and the sealer wears.

High-performance cement grouts add polymers and modified cements for a denser joint with better color consistency. For most kitchen walls and floors this is the sensible middle: a real improvement in stain resistance without the cost or difficulty of epoxy.

Premixed and urethane grouts

Premixed grouts are sold in a bucket, ready to trowel. The binder is a resin (urethane or acrylic in most products), not cement, so there is no water to measure and no pigment to mix unevenly. They resist stains without sealing and stay slightly flexible. Their limits are cure time and water exposure while curing, and makers restrict some of them in areas that stay wet. On a backsplash those limits rarely matter.

Epoxy grout

Epoxy grout is a resin and a hardener mixed just before use. The cured joint is dense, does not absorb, and stands up to the acids and degreasers that slowly attack cement. It is the strongest choice behind a range and on a kitchen floor in a busy household. The trade-offs are cost, a firm working time, and a slightly different look: epoxy joints have a smoother, more plastic sheen than cement, which some people notice on matte tile.

Sanded or unsanded

This question applies to cement grout. TCNA's guidance is direct:

• Joints smaller than 1/8 inch generally should be grouted with unsanded grout.
• Joints of 1/8 inch and larger should be grouted with sanded grout. The sand keeps a wide joint from shrinking and cracking.
• Joints larger than 3/8 inch usually need a more heavily sanded mix.
• Sanded grout should not be used on marble or other surfaces the sand could scratch.

That last point catches people out with polished stone, glass and soft glazed tile. If the tile scratches, the joint is planned narrow enough for unsanded grout, or a grout made for scratch-prone surfaces is used. The differences between tile materials are set out in backsplash tile materials compared.

Joint width

Joint width is not purely a style choice. It has to absorb the size differences between tiles. TCNA advises a joint of at least two times the average difference between the largest and smallest tiles, and says a joint under three times the tile-to-tile variation tends to look irregular. The installation standard ANSI A108.02 puts it as a requirement: the actual joint must be at least three times the actual variation in the tile's face dimensions.

In practice:

• Rectified tile has edges ground after firing to a precise size, so it can take a narrow joint.
• Standard pressed tile varies a little more and wants a moderate joint.
• Handmade and zellige tile varies a lot. A tight joint is possible, but the lines will wander and edges will sit proud.
• Large tile can have a slight bow along its length. A narrow joint makes any difference in height between neighboring tiles more visible, and TCNA notes that a flat surface matters more as tiles get larger and joints get narrower.

Ask the tile setter to dry-lay a few tiles at the proposed joint before committing. On a floor, joint width also affects cleaning and how the floor feels under a chair leg, which is covered in tile kitchen floors.

Sealing

Only cement grout needs sealing. A penetrating sealer soaks into the joint and slows absorption, which buys time to wipe up a spill. It does not make grout stain-proof, and it wears with cleaning, so it is reapplied on the schedule the sealer maker gives. Epoxy and premixed resin grouts are not sealed.

Separate from the grout, natural stone and some crackle-glazed and unglazed tiles are sealed before grouting so the grout pigment does not stain the tile itself. That is a tile requirement, and the tile's care sheet will say so.

Color

Grout color changes how the tile reads more than most people expect.

Very dark cement grout can show a pale mineral bloom, and very light grout shows cooking stains, so the extremes are where an upgrade in grout type pays back. Always judge color from a cured sample, since wet grout is darker. The design side, including undertones and matching grout to the counter, is in backsplash and grout colors.

Where grout does not belong

Grout is rigid. Wherever two surfaces move independently, a rigid joint cracks. TCNA says caulk should be used in place of grout at joints such as floor to wall, because those surfaces move independently of each other. In a kitchen that means flexible sealant, color-matched to the grout, at:

• the joint between the countertop and the first course of backsplash tile;
• inside corners where two tiled walls meet;
• where tile meets a window frame, cabinet side or door casing;
• the perimeter of a tile floor, where it meets walls and cabinets.

TCNA adds that acrylic caulk breaks down in wet horizontal joints and that silicone, urethane or multi-polymer sealants are better there. It also recommends allowing for expansion and contraction in every tile installation. In a small room a gap at the perimeter, hidden by the baseboard, is usually enough, and larger floors need visible movement joints. A cracked grout line in a corner a year after installation is almost always a joint that should have been sealant.

What to check before the grout is chosen

• Which ANSI standard the proposed grout meets, read from its data sheet.
• Whether the tile maker restricts sanded or epoxy grout on that tile.
• The joint width, agreed with the tile setter after looking at the actual tile.
• Whether the tile itself needs sealing before grouting.
• The grout color, approved from a cured sample next to the tile and countertop.
• That a matching flexible sealant is available in the same color.
• When the joints can get wet, and when (or whether) sealer is applied.
• That leftover grout, or at least the product name and color, stays with the house for repairs.

Who should choose which

• A backsplash away from the range, glazed tile, moderate budget: high-performance cement grout.
• Behind and beside the cooktop, or a white grout you want to stay white: epoxy, or a premixed resin grout the maker approves for the location.
• A kitchen floor with children, pets or a back door onto the yard: epoxy or high-performance cement in a mid-tone color.
• Polished marble or glass tile: a narrow joint with unsanded or other non-scratching grout.
• Handmade or zellige tile: whatever the tile maker recommends, tested on a sample board, in a color close to the tile.
• You want almost no grout: larger rectified tile with narrow joints, or a slab, as described in kitchen backsplashes and wall finishes.

JDI Construction specifies the grout type, color and joint width in the written selections, so they are not left to the day of installation. To plan tile as part of a remodel, see our Vancouver kitchen remodeling page.