Sand Types Used in Construction

Why sand type matters

Sand looks simple, but grain size, grading, shape and cleanliness all change how it behaves. A sand that makes excellent concrete can make poor mortar; a sand that compacts well as fill can be useless as a paver bed. Ordering by the right name — and checking what the supplier actually means by it — avoids most problems.

Concrete/mixing sand

Concrete sand is a manufactured or washed sand with a specific particle-size gradation suited to mix design, providing the fine aggregate portion of a concrete or mortar mix. Its gradation is more tightly controlled than many other sand products, since it directly affects the workability and strength of the finished concrete or mortar.

In the US, concrete sand is typically specified to ASTM C33, which sets grading limits and requires tests for fineness modulus, organic impurities, and clay lumps and friable particles, among others. It's relatively coarse and gritty, and it is usually washed to keep clay and silt within the specification's limits.

Masonry sand

Masonry (mortar) sand is finer and more uniform than concrete sand, which makes mortar smooth and easy to trowel into thin joints. It's specified under ASTM C144. Because it's fine, it isn't a good substitute for concrete sand in a concrete mix, and it's not recommended as a paver bedding layer.

Paver bedding sand

Bedding sand is the thin leveling layer directly beneath pavers. It is screeded to an even thickness, the pavers are laid on it, and the joints are then filled with a separate jointing sand.

The Concrete Masonry & Hardscapes Association (CMHA) guide specification for interlocking concrete pavement calls for bedding sand meeting ASTM C33 grading — the same grading as concrete sand — screeded to a nominal 1 in (25 mm). It says not to use stone dust or mason sand, and not to use bedding sand to fill low spots in the base. Joints are filled afterwards with a finer jointing sand or a polymeric sand.

How sand is specified

The specification tells you more than the product name. ASTM C33 covers concrete aggregates, including tests for grading and fineness modulus, organic impurities, clay lumps and friable particles, and soundness. ASTM C144 covers aggregate for masonry mortar, which must be graded within the limits it prescribes and limits deleterious substances.

Names such as 'mason sand', 'concrete sand' or 'fill sand' vary between suppliers, so ask which specification, if any, the material is tested to — especially for concrete, mortar or a paver bed.

Fill sand

Fill sand is a lower-cost, less tightly-graded sand used for general backfilling and grading where strength and precise gradation aren't critical — it's not typically suitable for concrete mixing or as a paver bedding layer, since it lacks the specific properties those applications need.

Quick reference

Why the distinction matters

Using a fill-grade sand in a concrete mix, or a mixing sand as paver bedding, can produce a weaker mix or a less stable paver surface than the application calls for. Always confirm with your supplier which product classification you're buying, especially for a structural or load-bearing use.

Worked example: bedding sand for a paver patio

A 12 × 16 ft paver patio with a 1 in bedding layer needs 12 × 16 × (1 ÷ 12) = 16 ft³ of sand, or 0.59 yd³. With the Sand Calculator's default 10% allowance, that's about 0.65 yd³ — roughly 0.88 tons at its default dry density of about 1,600 kg/m³ (about 1.35 tons per cubic yard). Wet sand weighs more, so the calculator offers a damp-sand option.

The base beneath the sand is a separate quantity. The Paver Sand Calculator and Paver Calculator cover the full build-up, and the paver sand and base guide walks through it.

Common mistakes

• Using stone dust or masonry sand as paver bedding.
• Buying unwashed fill sand for concrete or mortar.
• Converting yards to tons with a dry-sand density when the sand is wet.
• Screeding bedding sand too thick to make up for an uneven base — fix the base instead.