Concrete vs Mortar vs Grout: What's the Difference?

Here's what makes each product different and when to use which one.

The Quick Comparison

Property	Concrete	Mortar	Grout
Main ingredients	Cement + sand + gravel + water	Cement + sand + water	Cement + fine sand + water (no coarse aggregate)
Aggregate size	Coarse (3/8"–3/4" gravel)	Fine sand	Very fine sand or none
Typical strength	3000–5000 PSI	750–2500 PSI	750–3000 PSI
Primary use	Slabs, footings, structural	Bonding masonry, setting tile	Filling joints between tiles or pavers
Thickness	4"+ for slabs	3/8"–1" mortar beds	1/16"–1/2" joints

Concrete — For Structural Work and Slabs

Concrete is the structural workhorse. It contains Portland cement, fine sand, coarse aggregate (gravel), and water. The coarse aggregate gives concrete its strength — those pieces of gravel interlock under load and prevent the slab from cracking under compression.

Use concrete for:

• Slabs (patios, driveways, garage floors, sidewalks)
• Foundation footings
• Fence posts and anchor footings
• Retaining walls
• Steps

What concrete cannot do:

• Spread into thin joints (gravel is too coarse)
• Bond masonry units together (wrong adhesion properties)
• Fill tile grout joints (way too coarse)

For guidance on concrete strength and project matching, see what PSI concrete do I need and types of concrete.

Mortar — For Bonding Masonry and Setting Tile

Mortar contains cement and fine sand only — no coarse gravel. This lets it spread into thin, even layers and creates strong adhesion between materials. The lack of aggregate allows it to grip porous surfaces like brick and block more effectively than concrete.

Types of mortar:

• Type S mortar: High strength (1,800 PSI); for below-grade masonry, heavy stone, and outdoor applications. Most common for residential exterior work.
• Type N mortar: Medium strength (750 PSI); for above-grade masonry walls and veneers.
• Thinset mortar: Polymer-modified; specifically for setting tile. Available as gray or white.

Use mortar for:

• Laying bricks, blocks, and stone
• Setting ceramic, porcelain, or stone tile
• Repointing masonry joints (replacing old, crumbling mortar)
• Setting pavers with a mortar bed

What mortar cannot do:

• Replace concrete for structural slabs (not strong enough; no aggregate)
• Fill tile grout joints (wrong texture and porosity)

Grout — For Filling Tile Joints

Grout fills the spaces between tiles after they've been set in mortar. It contains cement, very fine sand (or no aggregate at all), and water. Some grout types include epoxy resins for stain resistance.

Types of grout:

• Sanded grout: Contains very fine sand; for joints 1/8 inch or wider.
• Unsanded grout: No sand; for narrow joints under 1/8 inch (polished tile surfaces).
• Epoxy grout: Most stain- and chemical-resistant; used in wet areas and commercial kitchens.

Use grout for:

• Filling joints between floor or wall tiles
• Filling joints between pavers (polymeric sand is often used instead)
• Finishing decorative concrete work

What grout cannot do:

• Set tiles (that's mortar's job)
• Replace structural concrete or mortar

Can You Substitute One for Another?

Concrete instead of mortar? No. Coarse gravel prevents concrete from spreading into masonry joints. The bond properties are also different.

Mortar instead of concrete? Not for slabs or structural work. Mortar lacks aggregate and achieves only a fraction of concrete's compressive strength. For thin applications (overlays under 1/2 inch), mortar-based products exist — but they're specialty items, not standard masonry mortar.

Grout instead of mortar? No. Grout has no adhesive function — it fills, it doesn't bond.

Concrete patching compound instead of grout? Definitely no. Way too coarse.

At the Hardware Store

You'll see these on the shelf together, which is why people confuse them:

• "Concrete mix" / "All-purpose concrete": Concrete. For slabs and structural work.
• "Sand mix" / "Mortar mix": Mortar-type product (cement + sand, no gravel). For overlays, masonry.
• "Masonry cement": Pre-mixed cement for mortar — you add sand yourself.
• "Thinset mortar": Tile-setting mortar. Comes in gray or white, standard or large-format.
• "Grout": Tile joint filler. Usually sold near tile.
• "Hydraulic cement": Fast-setting specialty cement for stopping water leaks. Not a general-purpose product.

The safest rule: match the product to the application. If the bag says "for slabs," it's concrete. If it says "for tile setting," it's thinset mortar. If it says "for joint filling," it's grout.

Related Guides

• Concrete vs Cement: What's the Difference? — The confusion between the binder and the finished product
• Types of Concrete — Specialty concrete mixes and when to use them
• How to Mix Concrete — Mixing procedure for bagged concrete