Sand, Gravel & Base Rock: Which Aggregate for Concrete, Pavers, Mortar and Drainage

Most aggregate mistakes are not about quality, they are about picking the wrong shape. Sand that is perfect under pavers will weaken a mortar joint. Rock that drains beautifully behind a retaining wall will never compact under a slab. The material all looks like sand and rock in the yard, but each one is graded and shaped for a specific job, and swapping them is what causes settled pavers, crumbling joints and slabs that crack in the first wet winter. This guide covers what each aggregate is actually for, and how to order it for an LA project.

Aggregate does three different jobs

Every aggregate on the list below is doing one of three things, and knowing which one tells you most of what you need. It is either filling out a cementitious mix, forming a compacted layer that carries load, or creating void space that lets water move. A material that is excellent at one of those is usually poor at the other two.

Two things the table cannot hold. The first is that "sand" is not one product; it is at least four, separated by how fine the grains are and whether the material has been washed. The second is the round-versus-angular distinction that decides everything about compaction. Rounded pebbles roll past each other forever and never lock up, which is exactly what you want in a French drain and exactly what you do not want under a driveway. Crushed angular rock interlocks and holds a compacted grade, which is why base material is always crushed.

Sand is four products wearing the same name

Start with the general-purpose material. All-purpose sand and medium grade sand are the everyday bagged sands for mixing concrete from Portland cement and aggregate, for bedding small flatwork, and for general fill. They are graded for mixing, not for a finished surface.

Plaster and masonry work want something cleaner and finer. Washed plaster sand is the material that goes into stucco base coats and mortar mixed on site, and the washing matters: silt and clay fines coat the grains and interfere with the cement paste bonding to them, which shows up later as weak joints and dusting surfaces. For volume masonry work, bulk washed masonry sand comes by the supersack rather than by the bag. If you are mixing your own rather than buying premixed, our mortar types guide covers what Type S, N and M actually change.

Hardscape sand is a third category entirely. Paver sand is the thin loose setting bed the pavers sit in, screeded flat and never compacted before the units go down. Polymeric sand is the opposite: it goes into the joints after the pavers are set and locks up when it is wetted, which is what keeps weeds out and stops the joints washing out in the first heavy rain. Using one in the other's place is the single most common paver failure, and our concrete paver guide covers the full assembly.

Finally there are the graded silica sands, sold by mesh number rather than by description, for filtration, blasting, sport surfaces and specialty mixes. Those are a topic of their own and we cover the numbering in our silica sand grades guide. Pool sand sits in the same family.

Gravel, crushed rock and what compacts

On the rock side the question is whether the material is round or crushed. All-purpose gravel and 3/4 in. gravel are the coarse aggregate that goes into concrete you mix on site with Portland cement and sand, and they are also the standard fill around perforated pipe in a French drain.

Crushed material is what you use when the layer has to hold a grade. Crushed rock in 3/4 in. comes by the supersack for the volumes a driveway, patio or wall backfill actually needs, and the angular faces are what let it compact and stay compacted. For hardscape specifically, paver base is the bagged version of that compacted subbase layer.

If the aggregate is going into concrete rather than under it, pre-mixed sand and rock saves proportioning two materials on site, and pairs with Type I/II Portland cement. For anything smaller than a footing or two, bagged premix is usually the better call, and our bagged concrete mix comparison covers which bag to reach for.

The Los Angeles cases that come up most

Three project types drive most aggregate orders here, and each one has a specific failure mode.

Hillside retaining walls are first. The backfill behind a wall is not decoration; it is the drainage system that keeps hydrostatic pressure from pushing the wall over, and it wants clean open crushed rock rather than native soil or fine sand. Our retaining wall guide covers the footing, drain and backfill sequence together.

Driveways and patios are second. Southern California soils move with moisture, and a slab or paver field over an uncompacted or undersized base is the one that telegraphs cracks by the second winter. Base depth and compaction do more for longevity than slab thickness does, and on the concrete side our slab reinforcement comparison covers what goes inside the pour.

Drought-tolerant yard conversions are third, and they are largely an aggregate purchase: base under decomposed granite paths, drainage rock in dry creek beds, and rock mulch where lawn used to be. Water still has to go somewhere when the rains come, which is where the gravel-filled drain line earns its keep rather than simply looking good.

Ordering: bags, sacks and the coverage math

The break point between bagged and bulk is roughly where carrying bags stops being the cheap part of the job. Bagged sand and gravel make sense for repairs, small footings, setting a few posts and topping up a bedding layer. Once you are covering an area rather than filling a hole, supersacks of masonry sand or crushed rock move the same material with far less handling.

Calculate by volume, not by area. Multiply the square footage by the depth in feet to get cubic feet, then convert: a 4 in. base layer is one third of a foot, so 100 sq. ft. of it is roughly 33 cubic feet before compaction. Add ten to fifteen percent for compaction on any base layer, because a compacted layer occupies meaningfully less volume than the loose material you ordered. Hardscape products such as paver base and paver sand are rated in square feet at a stated depth, which takes that math off your hands.

Order the sand, the rock, the cement and the Type S lime together where a mix calls for all of them, so a single missing component does not stop a pour. The full ranges are in the concrete aggregates collection and the wider mortars and aggregates collection. We deliver across Los Angeles County; send the square footage and the depth and we will work out the tonnage and put it on one truck.

Frequently asked questions

What is the difference between paver sand and paver base?

Paver base is the crushed, angular material that gets compacted under the pavers to carry load and hold grade. Paver sand is the thin loose layer screeded on top of it that the pavers actually bed into, and it is never compacted before the units go down. You need both, in that order.

Can I use all-purpose sand for mortar or stucco?

Use washed plaster sand instead. Mortar and stucco want a clean, finer, washed grade, because silt and clay fines interfere with the cement paste bonding to the grains and produce weak joints and dusting surfaces.

What gravel do I use for a French drain?

Clean, open-graded rock around the perforated pipe, wrapped in filter fabric. The whole point is void space for water to move through, so avoid material with a lot of fines, and avoid anything that will compact tight.

Is polymeric sand the same as paver sand?

No. Paver sand is the bedding layer under the pavers. Polymeric sand goes into the joints between them after they are set and hardens when wetted, which is what resists weeds and stops joints washing out in heavy rain.

How much base rock do I need under a patio?

Work it out by volume: square footage times depth in feet gives cubic feet. Add roughly ten to fifteen percent for compaction, since a compacted base occupies less volume than the loose material. Depth itself depends on soil and use, so check what your plans or the paver manufacturer call for.

Should I buy aggregate in bags or bulk?

Bags suit repairs, post setting, small footings and topping up a bedding layer. Once you are covering an area rather than filling a hole, supersacks move the same material with much less handling and far fewer trips.