How to Grout Mosaic Backsplash

Grouting a mosaic backsplash can seem daunting, but with some planning and the right tools, it can be a fun DIY project that really makes your kitchen pop. Here are some tips on how to properly grout a mosaic tile backsplash.

Selecting Grout

When grouting mosaic tiles, it’s important to choose the right type of grout. Here are some things to consider:

  • Sanded vs. unsanded – Sanded grout is best for joints wider than 1/8 inch. It provides strength and durability. Unsanded grout is best for smaller mosaic tiles with narrow grout lines. It can get into intricate crevices more easily.
  • Polymer modified grout – This contains polymers that make it more flexible, resistant to cracking and impervious to water. Great for kitchens.
  • Epoxy grout – Extremely durable and stain resistant but difficult to work with. Best for floors.
  • Color – Select a grout color that matches or complements your tile. Contrasting grout lines can make the design pop.

For most mosaic backsplashes, an unsanded polymer-modified grout is recommended. White or gray are popular colors.

Preparing the Surface

Proper prep is crucial for successful grouting:

  • Make sure tiles are firmly attached – Press on each tile to ensure it’s securely attached to the wall. Re-attach any loose tiles.
  • Clean tiles – Use a clean, damp sponge to wipe away any dirt, grease or dust. Ensure tiles are completely clean before grouting.
  • Remove spacers – Carefully remove any plastic tile spacers from between the tiles with needle nose pliers.
  • Wait for thinset to cure – Don’t grout until the thinset mortar has cured, usually 24-48 hours. Grout can pull away uncured thinset.

Mixing and Applying Grout

Mixing and applying grout takes some practice:

  • Mix grout – In a bucket, mix grout powder with water per manufacturer instructions. Let sit 5-10 minutes then re-mix. Proper consistency is thick but still spreadable.
  • Apply grout – Use a rubber grout float or squeegee. Push grout diagonally across the tiles to fill the joints. Apply even pressure and keep float at a 90° angle.
  • Work in small sections – Don’t grout a large area at once. Work in 3-4 sq. ft. sections so grout doesn’t dry before you can clean it.
  • Remove excess grout – Once applied, hold float edge at a 45° angle and scrape it diagonally across tiles to remove excess grout.
  • Clean with damp sponge – Once excess grout is removed, use a damp sponge to wipe diagonally across tiles to clean remaining film/haze. Rinse sponge frequently.
  • Check for missed spots – Scan for any areas you may have missed and touch up with grout as needed.

Curing and Sealing Grout

To finish:

  • Let cure – Don’t wipe or scrub tiles for 24-48 hours while grout cures. Just lightly damp sponge if haze appears.
  • Seal grout – Once cured, apply a penetrating grout sealer with a small paintbrush. This will protect from stains and water damage.
  • Avoid messes – Be careful not to spill foods, oils or cleaners on grout until sealed. Stains are difficult to remove once set.

With some careful prep and patience during application, you can achieve beautiful, professional-looking grouted mosaic backsplash. Maintain it well and your kitchen will enjoy a stylish, resilient accent wall.

Frequently Asked Questions About Grouting Mosaic Backsplashes

How long should I wait before grouting a mosaic backsplash?

It’s important to allow the tile thinset adhesive to fully cure before applying grout. This usually takes 24-48 hours. Grout applied too soon can be pulled out by uncured thinset leading to weak grout joints.

What’s the best grout color for a mosaic backsplash?

The most popular grout colors for mosaics are white and various shades of gray. Choose a color that matches or complements your tile colors. Contrasting grout can make the design stand out while matching grout creates a more seamless look.

Is epoxy grout good for kitchen backsplash?

Epoxy grout is extremely durable and resistant to stains. However, it can be tricky to work with. Regular polymer modified grouts are easier to apply and sufficient for kitchen use. Reserve epoxy grout for heavy-use areas like floors.

How do I prevent staining on my mosaic backsplash grout?

Sealing your grout after it fully cures is the best way to protect it from stains. Use a penetrating grout sealer formulated for your specific type of grout. Reapply yearly or as needed based on usage and wear. Also be cautious about spilling oils, sauces and cleaners on it.

Can I change the color of my existing mosaic backsplash grout?

Yes, you can apply a colorant to change existing grout. Clean thoroughly and make sure grout is in good condition first. Use a penetrating grout colorant formulated for mosaics following the product instructions. Test in an inconspicuous spot first.

How do I clean grease and soap scum from mosaic tile grout?

Gently scrub with an oxygen bleach cleaner and soft nylon brush. Baking soda or hydrogen peroxide pastes also work. Rinse well afterward and reseal cleaned areas. Avoid harsh chemical cleaners which can damage grout.


Grouting a mosaic tile backsplash brings this stunning design element together and really makes it pop. With some careful prep work, thoughtful material selection, and proper technique, you can achieve clean, uniform grout lines that complement the tile itself. Maintain the grout well with regular sealing and gentle cleaning and your mosaic backsplash will provide beauty and function for many years. With a little patience and TLC, you can handle this satisfying DIY project.