How to Install Slab Backsplash

Installing a slab backsplash can add an attractive, low-maintenance accent to your kitchen or bathroom. Slab backsplashes are made from materials like granite, marble, quartz, or porcelain, cut into a large single piece to cover the backsplash area. Installing a slab backsplash yourself can save significant cost compared to having it professionally installed. With careful planning and preparation, you can achieve beautiful results. This comprehensive guide will walk you through the entire slab backsplash installation process.

Choose the Right Slab Backsplash Material

The first step is to select your ideal slab backsplash material. Consider the pros and cons of each option:


Pros: Extremely durable, heat resistant, natural stone beauty

Cons: Expensive, can stain, needs yearly sealing


Pros: Elegant veining, heat resistant, natural material

Cons: Stains easily, etching from acids, yearly sealing needed


Pros: Resistant to stains and scratches, low maintenance

Cons: Manmade material, fewer color/pattern options


Pros: Impervious to stains, durable, various styles

Cons: Can chip if hit hard, prone to cracking if not installed properly

Granite and marble have the most natural appeal, but require yearly sealing. Quartz and porcelain are lower maintenance. Visit slab yards to view options in person.

Choose the Right Size Slab

Measure the existing backsplash area to determine the size needed. Include inside corners and allow an extra 1/4″ on all sides for adjustments. Standard slab sizes are:

  • 30″ x 72″
  • 30″ x 84″
  • 30″ x 96″

Avoid seams by using a single large slab if possible. Larger slabs reduce grout lines and give a sleek, seamless look. Custom slab sizes are also available.

Gather the Right Installation Supplies

Installing the slab backsplash yourself will require some specialty supplies. Be sure to have the following on hand:

  • 100% silicone adhesive caulk
  • Non-sanded grout in a color matching slab
  • Grout sealer
  • 1/4″ spacers
  • 2-part epoxy thinset mortar
  • Notched trowel
  • Stone sealer (for granite, marble)
  • Dust masks
  • Gloves
  • Safety goggles

Purchase high quality materials from reputable brands to avoid issues.

Prepare the Surface

Proper preparation is crucial for proper slab installation.

Remove Existing Backsplash

Carefully detach and pry off any existing tile backsplash. Be sure to wear goggles and gloves to protect from falling debris. Completely remove old thinset mortar down to the bare wall surface.

Deep Clean

Thoroughly wash the backsplash area with an appropriate cleaner degreaser. Scrub away all dirt, debris, soap residue and oils. Rinse several times. Allow to fully dry.

Evaluate Wall Surface

Wall surface must be 100% clean, dry and smooth to adhere slab. Fill any holes or cracks with hydraulic cement. Sand down high spots. Prime very porous drywall.

Mark Outlets

Carefully measure and mark the exact position of any outlets or switches on the wall. These will need to be cut out later.

Prepping the surface properly will ensure long-lasting bond strength.

Dry Fit the Slab Backsplash

Do a dry run before attaching the slab permanently.

  • Hold slab in place against wall. Have someone assist with large pieces.
  • Use spacers to leave 1/8″ gap between slab and wall. This allows room for adhesive and grout.
  • Mark cutting lines where outlet boxes protrude.
  • Test-fit all edges and corners. Make sure joints align evenly.
  • If needed, have slab professionally cut or trimmed to fit properly.

Dry fitting ensures you have the most accurate template for installation.

Mix Thinset Mortar

Follow all directions on thinset packaging closely to mix properly. Key steps:

  • Pour exactly the right amount of clean water in a bucket.
  • Slowly add powdered thinset mortar while mixing continuously with a paddle mixer.
  • Mix to a smooth, lump-free consistency.
  • Let sit 5 minutes then remix before using. This allows chemicals to react.

Proper thinset mixing prevents issues like cracking or bond failure later.

Spread Thinset Evenly

Use the notched trowel to spread a thin, even layer of thinset mortar on the wall area. Hold trowel at a 45 degree angle to rake across surface. Key tips:

  • Only spread enough thinset mortar that can be covered with slab within 15 minutes.
  • Maintain a consistent depth of thinset of 3/16″ to 1/4″.
  • Take extra care to fully fill the outlet cut-out areas.
  • Knock down any high ridges in thinset surface.

Applying thinset mortar evenly prevents voids behind the slab.

Set and Adhere the Slab Backsplash

Once thinset is prepared, carefully lift and set the slab:

  • Place spacers on countertop where slab will rest.
  • Lift slab with another person assisting if needed. Carry vertically so mortar doesn’t slip.
  • Gently place against wall, resting on spacers. Apply steady even pressure.
  • Slowly press and slide slab into final position. Do not let it drop or slip down wall.
  • Use a level across slab to ensure it is even. Shim spacers from below if needed.
  • Let adhesive mortar fully harden for at least 48 hours before grouting.

Taking care when setting the slab prevents cracks, chips or uneven gaps.

Cut Outlets in Slab Backsplash

Once placed, outlet holes can be precisely cut:

  • Put painter’s tape around the exact area to be cut. This prevents chip out.
  • Use a diamond blade wet saw to carefully cut holes the same size as outlet boxes.
  • Make multiple shallow passes when cutting to avoid cracking slab.
  • Diamond drill holes at corners to insert a jigsaw blade if needed for tight spots.
  • Dry fit slab and test that outlet covers can seat flush.

Careful outlet cutting allows uninterrupted slab installation.

Apply Silicone Caulk

Sealing joints and seams makes for a water-tight finish:

  • Load caulk gun with quality silicone bathroom caulk.
  • Run a smooth consistent bead along all joints between slab and wall.
  • Also caulk along the bottom where slab meets countertop.
  • Use a damp fingertip to smooth the caulk into any gaps or voids.
  • Wipe away any excess caulk with a clean rag before drying.

Caulking seals the slab installation and prevents moisture issues.

Mix and Apply Grout

Grout fills the thin spaces between the slab and walls:

  • Mix a small batch of unsanded grout per package instructions.
  • Holding grout float at a 45 degree angle, firmly press grout into seams.
  • Wipe diagonally across grout lines, cleaning off as you go.
  • Allow to dry until haze forms on surface, about 15 minutes.
  • Polish off haze with a clean, damp sponge. Rinse sponge often.
  • Clean any remaining film with a soft cloth once fully dry.

Proper grouting keeps the backsplash looking neat and new.

Seal and Polish Slab Backsplash

Sealing is an important final step:

Granite or Marble:

  • Use a premium quality stone sealer suitable for backsplashes.
  • Liberally apply sealer with a clean cloth or foam applicator.
  • Allow sealer to penetrate for 15-20 minutes.
  • Completely wipe away all excess sealer.
  • A second coat may be needed for porous granite or marble.

Quartz or Porcelain:

  • Use a cleaning polish made for the specific material.
  • Polish entire surface with a clean, soft cloth.
  • Re-polish as needed to maintain shine.

Sealing minimizes staining and makes cleaning easier.

With patience and care, a DIY slab backsplash can give your kitchen or bath a high-end, designer look. Be sure to properly seal and care for your slab backsplash. Enjoy your beautiful new accent wall for decades to come!

Frequently Asked Questions About Installing Slab Backsplashes

What tools do I need to install a slab backsplash?

You will need basic tools like a tape measure, level, mixer paddle, buckets, notched trowel, grout float, caulk gun, and non-scratch scrub pads. Specialized tools include a wet saw with a diamond blade for cutting, jigsaw, and oscillating tool. Safety gear like goggles, gloves, a dust mask, and knee pads is also recommended.

What’s the easiest slab material to install for a backsplash?

Porcelain is generally the easiest, most beginner friendly slab material to install. Porcelain has a naturally grippy surface texture that bonds well to thinset mortar. It is less prone to cracking or chipping. Porcelain also doesn’t require sealing like natural stone.

Should I get my slab backsplash professionally installed?

For high traffic kitchens or intricate designs, professional installation can ensure optimal results. Professionals have specialized tools and experience fitting and cutting slabs precisely. However, patient DIYers can certainly install their own slab backsplash successfully with proper planning and care.

What color grout should I use with a slab backsplash?

It is best aesthetically to use grout that matches the color of your slab backsplash as closely as possible. Having grout the same shade minimizes its visibility between the slab pieces. White grout can also work with lighter colored slab materials. Darker grout tends to look dirtier over time.

How do I cut holes in my slab backsplash for outlets?

Use a diamond blade wet saw to cut outlet openings following precise outlines marked with painter’s tape. Make several shallow passes when cutting to avoid cracking the slab material. You can also carefully drill holes at corners with a diamond bit before inserting a jigsaw blade to cut out the opening.

How long does slab backsplash installation take?

Expect the installation process to take 2-3 days in total. Day 1 for removal and prep work, Day 2 for actually adhering the slab and letting it set, and Day 3 for grouting, sealing, and polishing. Actual hands-on time will be around 8-12 hours depending on the size of your backsplash area.

Should I seal my natural stone slab backsplash?

Definitely seal granite, marble, travertine, or limestone backsplashes. Use a penetrating sealer made for those natural porous stones. Sealing makes them stain resistant and easier to clean. Quartz and porcelain backsplashes do not need sealing.

How do I cut a slab backsplash to fit around an outlet?

Outline the exact area to be cut with painter’s tape first. Use a wet saw with diamond blade to cut openings, making multiple shallow passes. You can also drill small holes at corners with a diamond bit before inserting a jigsaw blade to cut out the opening. Take care not to crack the slab.

What kind of thinset should I use to install a slab backsplash?

It is best to use a high quality thinset mortar designed specifically for natural stone tile or for large format tile. These “medium bed” mortars provide greater adhesion strength and flexibility needed for slabs. Make sure to mix the thinset per directions.

Can I install a slab backsplash directly over existing tile?

It is not recommended to install a slab directly over existing tile. The different planes can allow moisture to get behind the slab and cause bonding issues. It is best to remove existing tile down the bare wall and start fresh with proper preparation of the surface.


Installing a slab backsplash can take your kitchen or bathroom from basic to spectacular. With some careful planning and elbow grease, you can tackle this project yourself and save on installation costs. Focus on proper preparation, patience during cutting and setting, and proper sealing. Your new stone, quartz, or porcelain slab backsplash will bring elegance and function to your living space for many years. With this step-by-step guide, you can gain a sense of accomplishment transforming your home with a beautiful new slab backsplash installed with your own hands.