How Much Mortar for Backsplash

Backsplashes are a great way to add visual interest and protect the walls behind kitchen counters, bathroom vanities, and more. When installing a backsplash, it’s important to use the right amount of mortar. Using too little mortar can result in tiles that aren’t adhered properly and may fall off. Using too much mortar creates a mess and leads to uneven tiles. So how much mortar should you use for a backsplash? Here’s a comprehensive guide on determining the right amount of mortar for backsplash projects.

Factors That Determine How Much Mortar is Needed

Several key factors impact how much mortar you need for a backsplash installation:

Tile Size

  • Smaller tiles require more mortar since there are more grout lines to fill.
  • Larger tiles require less mortar since they have fewer grout lines relative to the surface area.
  • As a general guideline, use about 1/4” thickness of mortar for tiles smaller than 4”x4”. Use 1/8” to 1/4” thickness for larger tiles.

Tile Type

  • Textured tiles with uneven backs require more mortar to fully adhere and prevent voids.
  • Smoother tiles can be adhered with a thinner mortar bed.

Surface Flatness

  • Surfaces that are perfectly flat and plumb require less mortar.
  • Surfaces with more inconsistencies need more mortar to fill gaps and create a level tile base.

Mortar Type

  • Mortar that needs to be mixed to a thinner consistency requires more volume to achieve the right thickness.
  • Pre-mixed mortar that is thicker may require less material.

Trowel Size

  • The size of the trowel’s notches determines mortar thickness per application. Bigger notches lay down more mortar in each pass.

Environmental Factors

  • Hot, dry climates cause mortar to dry out faster, potentially requiring fresh batches more frequently.
  • Cool, humid climates keep mortar workable longer before drying.

How to Calculate Exact Mortar Needs

While the above factors impact mortar needs for backsplash installation, you can use some simple calculations to determine amounts even more precisely.

Calculate Surface Area

First, measure the length and height of the backsplash area to find the total surface area in square feet. This is done by multiplying the length x height.

For example, if the backsplash is 8 feet long and 4 feet high, the area is 8 x 4 = 32 square feet.

Be sure to calculate the total area of all surfaces receiving tile, such as multiple walls in an L-shaped backsplash.

Estimate Thickness

Next, estimate the mortar thickness needed. As a starting point, use 1/4″ thickness for small mosaic tiles and 1/8″ for larger tiles. Then adjust depending on tile type, surface flatness, and other factors.

If 1/4″ thickness is needed, for example, then for each square foot you’ll need 0.25″ of mortar.

Calculate Volume

With the area and thickness estimates, you can now calculate the volume of mortar needed in cubic feet. Simply multiply the area by the thickness.

For our 32 square foot backsplash that needs 1/4″ mortar, the calculation would be:

32 square feet x 0.25″ (converted to feet) = 8 cubic feet

This gives the total volume of mortar required for full coverage at the desired thickness.

Convert to Mortar Amount

Finally, convert the cubic feet result to the actual amount of mortar product needed according to the manufacturer specifications.

Bagged mortar mixes will indicate coverage amounts, such as 50-60 sq ft per 50 lbs. With our example of an 8 cubic foot job, if the product covers 60 sq ft per bag, you would need approximately 2 bags (8 ft3 / 60 ft2 per bag = 0.13 bags).

For premixed buckets, verify coverage in cubic feet or inches per gallon. Calculate how many gallons or buckets are needed for the full volume.

Carefully measuring the space and doing these volume calculations will help ensure you buy the right amount of mortar for efficient backsplash installation. Allow a little extra as a buffer.

How to Apply the Right Amount of Mortar

With the right quantity of mortar materials on hand, now you need to properly apply it to achieve an optimal backsplash. Here are some tips:

  • Mix to a toothpaste consistency. Mortar that is too thin will slide right off the wall. Mortar that is too thick will be hard to evenly spread. Aim for a sticky, pasty consistency similar to toothpaste.
  • Force it into the surface. Don’t lightly sprinkle dry mortar or just gently smear it on. Really press and compact the mortar into the surface for maximum adhesion.
  • Use the notched edge. Hold the trowel at a 45 degree angle and scrape the notched edge firmly down the substrate to leave evenly thick ridges of mortar.
  • Check thickness with a tile. Place a tile into the mortar bed to make sure the notches have left enough depth for proper contact and adhesion on the back of the tile.
  • Apply in sections. Work in 2-3 square foot sections so the mortar doesn’t dry out before tiles are set.
  • Replenish as needed. Be prepared to mix up fresh mortar as you go to maintain the ideal texture for application.

Taking the time to regularly check application thickness and consistency will help guarantee proper installation.

Troubleshooting Mortar Issues

No matter how carefully you calculate and apply mortar, occasional issues can arise. Here are some common problems and solutions:

Problem: Tiles sliding out of position

Solution: Mortar is too thin or hasn’t properly cured. Remove tiles and mix up stiffer mortar, then reapply.

Problem: Mortar drying too quickly

Solution: Mix in smaller batches and work in smaller sections to ensure it stays workable. Tent area with plastic to prevent fast evaporation.

Problem: Gaps behind tiles

Solution: Mortar wasn’t pressed into the wall sufficiently. Remove tiles and increase mortar thickness by applying more force.

Problem: Uneven tile faces

Solution: Mortar layer was inconsistent. Use larger notched trowel and maintain even 45 degree angle as you spread mortar.

Monitoring application and being willing to redo sections will reduce headaches once tiles are set. Careful prep leads to quality long-lasting installations.

Tips for Efficient Mortar Application

Proper planning, preparation, and application techniques will keep your backsplash mortar needs and usage on track:

  • Carefully measure all surfaces receiving tile and make precise calculations before mixing or purchasing materials.
  • Gather all necessary supplies – mortar, trowels, sponges, buckets – before starting so you can work efficiently.
  • Prepare the surface thoroughly by cleaning and scoring glossy substrates.
  • Opt for large notched trowels to achieve the right thickness more quickly.
  • Mix mortar in small batches to prevent premature drying before use.
  • Apply mortar inManageable sections of 2-3 square feet.
  • Have a helper prepare fresh mixes as needed to avoid lapses.
  • Work methodically and attentively to achieve even consistent adhesion.
  • Be willing to redo areas if the results aren’t satisfactory.

Proper planning, preparation, and application techniques will keep your project on track and avoid tile disasters. With the right amount of quality mortar and some diligent effort, you can achieve beautiful backsplash results. Let the above guide equip you with knowledge to complete this project like a pro.

Frequently Asked Questions About Mortar for Backsplashes

Many questions come up when calculating needs, purchasing, and working with mortar on backsplash installations. Here are answers to some of the most common questions.

How much mortar do I need for a standard backsplash?

For a typical 4×8 foot backsplash made of 4 inch tiles, you will need about 5-6 bags of dry mortar mix or 2-3 buckets of premixed mortar. Make sure to calculate your exact area and thickness needs based on the specific tile to get an accurate estimate.

What type of mortar should I use?

Use white unmodified thinset mortar that meets ANSI A118.1 specifications. This high bond mortar is ideal for backsplashes. Avoid multipurpose or premixed organic mastic, which has lower bond strength.

Is mortar and thinset the same thing?

Yes, the terms mortar and thinset are used interchangeably to refer to cement-based mixes used for bonding tile. Thinset gets its name from the thin layer of application – usually 1/4″ or less.

Can I use leftover thinset mortar if it is still workable?

Only mix up as much mortar as you can use in about 2 hours. Fully dried mortar cannot be reused. Partially dried mortar can potentially be reconstituted if it hasn’t hardened significantly. But fresh mixes are always preferred.

How long does mortar take to dry before grouting?

Wait 24-48 hours after applying tiles before grouting. Drying time depends on temperature, humidity, and mortar thickness. Test by firmly pressing on a tile – if it no longer moves, the mortar has dried.

Should I mix mortar by hand or use a drill mixer?

Using a drill with a mixing paddle attachment makes mixing mortar much faster and easier. Just be sure to blend for the time specified on the packaging instructions. Hand mixing in small batches is more laborious but can be done when needed.

How can I tell if mortar coverage is adequate?

Remove a tile and inspect it after embedding it in the mortar. There should be full contact between mortar and tile, without any gaps, and mortar should cover at least 80% of the tile back to be considered sufficient.


Installing a stunning backsplash brings functionality and style to kitchens, bathrooms, and other rooms throughout your home. With proper planning and application of mortar, this relatively simple upgrade can be completed successfully by DIYers. Determining how much mortar to purchase and apply for backsplashes requires careful surface measurements, volume calculations, and thickness estimates based on your specific tile selection. Mixing mortar to toothpaste consistency and forcibly applying it to the wall in manageable sections will allow you to embed tiles in a durable, lasting bond. With the techniques outlined here, you can feel confident tackling this project and gaining satisfaction from enhancing your living spaces with beautiful backsplashes.