You’ve probably heard the terms mortar and grout used interchangeably before, but you may not know these products actually differ significantly. While mortar and grout are both cement-based construction materials, they differ significantly in terms of usage, makeup, texture, and strength.
If you’re planning a DIY project involving tile installation, then you’ll need to be familiar with both of these materials. Using mortar instead of grout (or visa-versa) will result in a poor-quality installation which may need to be completely re-done.
Let’s take a closer look at mortar vs grout, so you’ll be well prepared to complete that DIY project you’ve been putting off.
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Mortar
Mortar is an adhesive cement used to stick one material to another. It’s made from a mixture of cement, sand, water, and additives for increasing bonding, flexibility, and water resistance. It forms a smooth, buttery consistency that sticks to a trowel almost like peanut butter to a spoon.
When compared with typical concrete, mortar has several major differences. It doesn’t have the same level of strength as concrete, has a higher air content, and also has the ability to retain more water.
The reason mortar doesn’t need to have the same strength level as concrete is that you generally want mortar to be the weak point in your masonry job. That way, if things shift over time, it’s the mortar that breaks instead of the bricks or the tile. Then, repairing the masonry is as simple as cleaning out crumbling mortar and replacing it with fresh mortar.
One of the most commonly used mortars in DIY is thinset mortar. This is a mortar specifically formulated for securing tiles to cement, stone, or backer board. It’s designed to be used in relatively thin layers and has excellent bonding capabilities.
Grout
Grout is a cement-based filler product designed to flow and fill gaps left in tiles as well as for sealing sections of precast concrete. Unlike mortar, it’s not primarily an adhesive, rather it’s a sealer and gap-filler.
Because it’s designed to flow into small gaps, it’s much thinner and more viscous than mortar. This viscosity makes it ideal for filling in tiny gaps that would be difficult or impossible to get mortar into. You’ll find some type of grout in between tiles on your bathroom or shower floor.
Grout comes in a variety of colors and as well as either powdered or pre-mixed forms. There are also several different types of grout, which are tailored for slightly different applications.
Types of Grout
- Unsanded grout: Unsanded grout is used for tiles with gaps of less than 1/8”. The lack of sand makes it stickier than other grouts, which is why it’s used for tiling vertical surfaces like shower and bathroom walls.
- Finely sanded grout: This grout is used for floor tiling where the joints are between 1/8” and 3/8” wide. It features a fine aggregate inside the mixture, which makes a good general use grout for a variety of tiling jobs.
- Quarry-type grout: Quarry-type grout contains a coarser grade of sand, and is used for filling joints up to ½” wide. Its makeup is nearly the same as finely sanded grout, except it uses grainier sand.
- Epoxy grout: This grout is slightly different from the above types. It contains both an epoxy resin and a hardener, which makes it extremely strong as well as being moisture and stain-resistant. It’s often used for kitchen countertops, or other areas where stains frequently occur.
Mortar vs Grout Comparison
Now that you’ve got a solid grasp on the basics of mortar vs grout, let’s take a closer look at the differences between the two materials.
| Mortar | Grout | |
| Primary Use | Adhesive for brick, stone, and tile. | Filler material for gaps between tiles. |
| Viscosity | Low | High |
| Workability | Easy to work with, sticks to a trowel like a fluffy paste. | Less workable, difficult to work with a trowel. |
| Water Content | Low | High. Needs more water to achieve desired consistency. |
| Drying Time | Higher | Lower |
| Strength | Lower | Higher |
Applications of Mortar vs Grout
Both mortar and grout are cement-based construction materials, but that’s where the similarities end.
Mortar is a bonding material used to joint bricks, blocks, or ceramic tile. It’s highly workable and achieves a consistency similar to smooth peanut butter or bondo. In fact, one of the ways you know your mortar has achieved the right consistency is when the trowel will stand upright without falling over in the mixture. Mortar can be made in a variety of different ways, with some methods utilizing lime or other additives.
Grout is a gap-filler and sealer designed to flow between the narrow gaps between ceramic tile. It’s thin and viscous and is trickier to work with a trowel than mortar is.
Strength
When it comes to the strength of the two materials, you might be surprised to learn that grout is generally stronger than mortar.
This might seem counterintuitive, as you might think the stuff needed for building brick walls would be stronger than the gap filler for the tile in your bathroom. The reason for this is you generally want the mortar to be the weak point in any masonry project. That way, if anything fails, it’s the easy-to-fix mortar rather than the difficult to repair brick.
Compressive strength is the metric used to measure cement-based materials. It’s a measurement of a material’s ability to withstand pressure and is measured in pounds per square inch (PSI).
Typical mortar strength after curing falls somewhere between 750 and 2500 PSI depending on the specific type. Grout on the other hand generally falls somewhere between 2,500 and 5,000 PSI.
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