How to Grout a Backsplash: Grout Types, Steps and Sealing

Grout covers a sliver of a backsplash by area and tends to be the first thing you notice when the job goes wrong: uneven lines, a chalky film on the tile, a crack along the counter a few months later. If you are working out how to grout a backsplash for the first time, most of the skill is in the timing: when to mix, when to wipe, and when to leave the wall alone. This guide covers the choice of grout, the work itself, and the joints that should never see grout at all.

Before the grout: is the wall ready?

Grout goes in only after the tile adhesive has cured. For a standard thinset mortar, grout makers typically ask for 24 to 48 hours. Premixed tile adhesive can need up to three days, and rapid-setting mortars much less. The data sheet for your adhesive outranks any rule of thumb. Our guide to whether the countertop or the backsplash goes in first lays out the order of work.

Then prepare the joints. Pull every spacer. Scrape out mortar that squeezed up between tiles so that roughly two thirds of the tile's depth is open for grout; a shallow spot cures to a different shade. Vacuum the dust, wipe the tile faces, cover the countertop, and switch off power to any outlets in the backsplash before you work a wet sponge around them. Porous stone and matte or textured tile can stain permanently, so check whether yours needs a sealer or grout release first.

Which grout to use on a backsplash

Start with the width of the joint, then consider how easily the tile face scratches.

• Unsanded cement grout. The classic choice for joints up to 1/8 inch. With no sand grains to bridge a narrow gap, it packs fully into tight vertical joints, and it is the safer pick for polished stone, glass and other faces that scratch.
• Sanded cement grout. Sand gives it body for joints of 1/8 inch and wider, where an unsanded mix can crack. The same sand can scratch some glass, metal, marble and glazed tile, so test a spare piece first.
• High-performance cement grout. Polymer-modified blends, many of them rated for joints from 1/16 to 1/2 inch, with more consistent color. Some are sold as needing no sealer.
• Premixed, ready-to-use grout. Sold in a tub with no mixing, and generally no sealing afterward. It is spread over a small area and cleaned almost immediately, and because it cures by drying, some products ask for about a week before the wall gets wet.
• Epoxy grout. Highly stain-resistant and in no need of sealer, but the least forgiving to apply. It works on a fixed clock, and any film left on the tile has to come off before it cures.

The 1/8-inch dividing line is the traditional rule, and newer formulas blur it, so read the joint range printed on the package. A mosaic that pairs glass with metal caps is a case for unsanded grout, as we cover in our comparison of the glass and metal tile backsplash.

On color: grout close to the tile color reads as one surface, while a contrasting grout outlines every tile and every wandering line.

How to grout a backsplash, step by step

You need a rubber grout float, a margin trowel, two buckets, a grout sponge and cheesecloth or soft cloths, plus nitrile gloves, safety glasses and a dust mask for mixing. The steps below are for powdered cement grout. Premixed and epoxy grouts run on a different clock, with cleanup starting within minutes, so follow the label for those. Small mosaics, with many more joints, take several times the grout that large tile does, so check the coverage chart before you buy.

1. Mix to the bag. Measure the water, add the powder to it, and stir to a smooth, creamy paste. Let it rest for the slake time on the bag, commonly about five minutes, then stir again. Never loosen a stiffening batch with more water. That weakens the grout and causes blotchy color.
2. Pack the joints. Hold the float at roughly 45 degrees and push the grout across the joints diagonally, pressing so it fills the full depth instead of bridging the top. Spread only as much as you can clean within about half an hour.
3. Strike off the excess. Turn the float nearly upright and pull it diagonally across the tile, like a squeegee. Moving on the diagonal keeps the edge from digging grout back out.
4. Wait, then sponge. Let the grout firm up, typically 15 to 30 minutes, or until none transfers to a fingertip. Then wipe lightly with a sponge wrung until it no longer drips, rinsing often in clean water. Too much water at this stage washes out pigment and leaves joints soft and powdery.
5. Shape the lines. A final light pass with the sponge along each joint evens the depth.
6. Buff off the haze. Once a pale film shows on the tile, usually one to three hours in depending on the product, polish it away with cheesecloth or a barely damp sponge. Haze left for days hardens and may call for a dedicated remover.

The joints you do not grout

Three places on a backsplash get a flexible sealant instead: the line where tile meets the countertop, the inside corners where two walls meet, and any edge where tile ends against a cabinet, a window frame or another material. Grout manufacturers and the tile industry's own guidelines treat every change of plane as a movement joint. Counter and wall shift independently, and rigid grout in that seam is a classic cause of the crack that later opens along the counter.

Leave those joints open while you grout, then fill them once the grout has cured, usually the next day. A 100 percent silicone sealant is the usual recommendation, and several grout makers sell color-matched caulk.

Curing, sealing and the first weeks

Cement grout is firm by the next day and goes on curing well after that. Keep the wall dry and skip the routine cleaning for as long as your product states; published figures run from three days to three weeks.

Sealing depends on the grout. Standard cement grout is porous, and many makers list a sealer as optional; many tilers still apply a penetrating one in a kitchen. Use it only after the grout has cured. Most instructions quote 48 to 72 hours, and the sealer's own label has the final word. Epoxy, premixed grouts and several high-performance cement formulas are made to go without. How often to reseal depends on the sealer, so go by its label.

Regrouting a backsplash that has seen better days

Stained or crumbling grout does not mean the tile has to come out. A thin skim of new grout over old does not hold, though. The tile industry's guidance is to remove at least two thirds of the old grout's depth, and one major manufacturer accepts half, provided what remains is sound. A carbide grout saw or an oscillating tool with a grout blade does the raking. Wear eye protection and a dust mask, and work slowly so the blade does not chip the tile edges.

The backsplash with nothing to grout

Everything above belongs to mortared tile, and it adds up to several days of setting, grouting and curing before a few square feet of wall are finished. Some backsplashes skip the sequence entirely. WallWear's metal tiles are real, water-resistant aluminum, 8 by 8 inches, embossed, with an adhesive backing. The product page puts it in one line: no grout, no special tools, and no professional help required. Tiles sit edge to edge and trim to fit with a box cutter or scissors.

What you get is a field of embossed metal with tight seams where grout lines would be. Rustic Farmhouse sets intricate gold ornamental detailing on a soft green background, Silver Fleur has a polished silver finish with fleur-de-lis inspired patterns, and Patina Copper pairs a rich copper tone with a weathered patina finish. The tiles need a clean, dry, smooth wall, are not suitable for textured ones, and should sit at least 10 inches from the stovetop, per the product page. We answer whether you ever grout peel and stick metal tile in a separate piece, and the full method is in our guide on how to install peel and stick metal tile.

Frequently Asked Questions

Do you use sanded or unsanded grout for a backsplash?

It depends on the joint. Unsanded grout suits joints up to 1/8 inch and is the safer choice on polished stone, glass and other surfaces that scratch. Sanded grout is made for joints of 1/8 inch and wider. Some newer grouts are rated for both ranges, so check the joint width printed on the package before you buy.

Do you grout between the backsplash and the countertop?

No. That seam is a change of plane, where the counter and the wall move independently, and rigid grout there tends to crack. Keep grout out of the joint and fill it with a flexible sealant, usually 100 percent silicone, once the grout has cured. Inside corners and edges against cabinets get the same treatment.

How long does backsplash grout take to dry?

Cement grout is usually firm by the next day, but curing takes longer and varies by product. Follow the package for when the wall can get wet and when routine cleaning can start. Most instructions allow sealing after 48 to 72 hours. Premixed grouts cure by drying and can need about a week before they see water.

Do you have to seal grout on a kitchen backsplash?

Not always. Standard cement grout is porous, and although many makers call sealing optional, many tilers still apply a penetrating sealer in a kitchen, particularly behind the cooktop. Epoxy, premixed grouts and several high-performance cement grouts are made to go without sealer. Check the label on yours, and let the grout cure before sealing.

Can you put new grout over old grout?

Not as a thin skim, which does not hold. Tile industry guidance is to rake out at least two thirds of the old grout's depth first, using a grout saw or an oscillating tool with a grout blade, then vacuum and regrout. The tile itself can stay where it is.