How to Grout Uneven Stone Backsplash

Grouting a stone backsplash can seem daunting, especially if the stones are uneven. However, with some preparation and the right techniques, it is possible to achieve a beautiful, professional-looking finish. Here is a step-by-step guide on how to grout an uneven stone backsplash.

Clean and Prepare the Surface

Before grouting, it is important to make sure the stone and grout joints are clean and free of dust, dirt, oil, and sealers. Use a damp sponge to wipe down the surface. For a more thorough clean, use a grout cleaner or mix up a solution of 1 part white vinegar to 1 part water and scrub with a stiff bristle brush. Rinse thoroughly and allow to dry completely.

Apply Grout Release/Sealer

Applying a grout release or sealer along the edges of the stone tiles before grouting will make clean-up much easier. Use a small paintbrush to brush the sealer along the tile edges and wipe off any excess. This will prevent the grout from sticking to the surface of the tiles.

Mix the Grout

For unsanded grout, mix the grout powder with water or a grout additive according to the manufacturer’s instructions. The grout should have a thick, creamy consistency. For sanded grout, mix the grout powder with water until it has a stiff, dough-like consistency. Allow the grout to sit or “slake” for 5-10 minutes before using. This allows the grout to fully absorb the water.

Apply the Grout

Using a grout float or rubber grout float, apply the grout diagonally across the joints, pressing firmly to fill any gaps. Make sure to fully pack the grout into the joints, keeping it flush with the surface of the tiles. Apply grout in small sections so it stays workable.

For uneven tiles, you may need to apply a bit more pressure with the float to fill wider or deeper joints. Take care not to scrape the edges of the tiles. Wipe off any excess grout from the surface of the tiles with a damp sponge as you work.

Clean Up and Finish

Once the grout in a section starts to firm up, after about 15-30 minutes, begin the clean-up process. Using a damp sponge, wipe diagonally across the tiles to remove any grout haze. Rinse the sponge frequently and change the water often.

For a smooth finish, wait for the grout to fully cure, usually 24-48 hours, then buff the grouted area with a soft cloth. Avoid any harsh scrubbing during clean-up or you may pull grout out of the joints.

Sealing the grout once fully cured will add protection and waterproofing. Use a grout sealer recommended for stone and apply according to product directions.

With some care and patience, it is possible to achieve beautiful results when grouting an uneven stone backsplash. Proper preparation, technique, and clean-up will help ensure your grout lines come out looking perfect.

Tips for Grouting Uneven Stone Backsplash

  • Use unsanded grout for joints 1/8 inch or smaller and sanded grout for wider joints up to 1/2 inch. The sand in sanded grout helps fill larger gaps.
  • Choose a grout color that matches or complements the color variation in the stone. Lighter grout colors work well with busy stone patterns.
  • Cut rigid foam board or cardboard to size and place in the openings of cabinets or outlets. This prevents grout from falling in while providing a uniform grout line.
  • Grout small sections at a time, no more than 4-5 square feet. This prevents the grout from drying too quickly before it can be cleaned up.
  • To help fill in any low spots, use the edge or point of the grout float to firmly pack the grout into the joint.
  • Grout release agents help minimize staining or hazing on porous, absorbent stones like limestone, travertine, and sandstone.
  • For wider joints, press sanded grout into the gap in layers, letting each layer dry before adding more. This prevents sagging or cracking in wider grout lines.

Common Issues When Grouting Uneven Stone

Grouting uneven stone does take a bit more skill and effort compared to grouting smooth tile. Here are some common issues that may arise and how to avoid them:

Cracking or Crumbling Grout – If the grout mixture is too thin or tiles are not fully adhered, grout may crack or crumble out of joints. Be sure to mix grout to the proper consistency and allow adequate cure time.

Pitted, Low Grout Lines – Grout may sink into deeper joints and low spots in uneven stone. Carefully pack grout into low areas with the grout float and allow each layer to dry before adding more.

Grout Haze – Grout residue left on the surface of textured stone can be difficult to remove. Work in small sections, wiping up excess before it dries. Use grout release and sealers to minimize hazing.

Staining or Discoloration – Pigmented grout that is not properly sealed can stain porous stone over time. Use a compatible grout and tile sealer to protect against staining.

Grout Cracking Over Time – Improper grout curing or repeated heating/cooling cycles may cause hairline cracks. Allow new grout to cure fully before exposing to elements. Use flexible epoxy grout for higher-movement areas.

Frequently Asked Questions

What type of grout should I use for an uneven stone backsplash?

For most stone backsplashes, unsanded grout is recommended for joints up to 1/8 inch wide. It is smoother and flows easily into narrow, uneven joints. Use sanded grout for wider grout lines between 1/8 and 1/2 inch.

How do I get the grout into low spots and holes in uneven stone?

Use the pointed corner of the grout float to firmly pack the grout into low areas and holes. Allow each layer of grout to dry for 30 minutes, then apply another layer until it is flush with the tile surface.

Should I seal my stone backsplash before or after grouting?

Sealing prior to grouting will help minimize staining from the pigment in colored grouts. Be sure to allow sealer to fully cure before grouting, usually 24-72 hours. An additional seal after grouting adds further protection.

What is the best way to remove grout haze from textured stone?

Use a grout haze remover formulated for natural stone or a mild acid-based cleaner after initial grout clean-up. Agitate with a stiff nylon brush, then rinse thoroughly. Avoid acidic cleaners on polished marble, limestone or travertine.

How long should I wait before sealing grout on a stone backsplash?

Grout should cure fully for a minimum of 72 hours before applying any sealer or finishing treatments. This allows moisture to evaporate so the sealer can properly bond to the surface.


Grouting stone with an uneven surface presents some unique challenges, but is definitely achievable with the right approach. The keys are proper tile prep, using the right grout for the joint size, applying in thin layers, packing tightly into low spots, and thorough final cleaning. Sealing both before and after grouting will help ensure the finish resists staining and holds up beautifully over time. With some patience and the proper techniques, an uneven stone backsplash can be transformed into a stunning focal point in the kitchen.