Sand looks like the least interesting thing on a building site. It's also behind some very expensive problems. The wrong sand in mortar gives you crumbling joints and white staining on your brickwork. Poorly compacted fill under a slab can settle and crack it. And you'd never know which sand went where unless you asked.
Here are the sands you'll actually hear about on a Queensland house build, where they go, and what to look out for.
Why the type of sand matters
Sands differ in grain size, grain shape and how much clay, silt and salt they carry. Those differences decide:
- How workable a mix is. Fine, slightly clayey sand makes smooth mortar. Coarse, clean sand makes stronger concrete.
- How strong and durable the result is. Too much clay or silt weakens concrete and mortar and increases shrinkage.
- How well it compacts and drains. Fill and bedding sands need to compact firmly and, in some cases, let water through.
The sands on a house build
Brickies' sand
A fine sand with a small amount of natural clay, which makes mortar "fatty" and easy to work. It's what your bricklayer uses with cement and lime for mortar. Colour varies by quarry, so it's also part of why mortar colour can change between batches. It should be clean, without lumps, roots or rubbish, and not so clayey that the mortar shrinks and cracks.
Where you'll see it: brickwork and blockwork mortar.
Washed sand (concrete sand)
A coarser sand that's been washed to remove clay, silt and organic matter. Concrete sand is graded to AS 2758.1 so it packs tightly with the cement and stone. In South-East Queensland it's commonly a blend of washed natural sand and manufactured sand.
Where you'll see it: in the premixed concrete for your slab and footings (you won't see it separately, as it arrives in the truck), and in render and screed mixes.
Manufactured sand
Made by crushing hard rock to sand size. The grains are more angular and consistent than natural sand, and supply doesn't depend on river or dune extraction. It's widely blended into concrete sand, and some is used in mortar and render.
Where you'll see it: mostly in premixed concrete and blended sands from the supplier.
Plasterers' sand
A fine, clean, well-graded sand for render, often a washed river sand. Too coarse and the render is hard to finish; too much clay and it can crack.
Where you'll see it: cement render on blockwork or brick walls.
Packing or fill sand
Used to build up levels under slabs, behind retaining walls and around footings. It's only as good as its compaction. Fill must be placed in layers and compacted, and under a slab it should be tested and certified as required by your engineer. Sand fill with a lot of clay or organic matter compacts poorly and can settle later.
Where you'll see it: under the slab, in levelling the building pad, backfilling around the house.
Paver bedding sand
A coarse, clean sand screeded flat as the bed for pavers. Fine or clayey sand holds water and lets pavers move and sink.
Where you'll see it: driveways, paths and patios.
Pipe bedding sand
A clean, coarse sand or fine aggregate laid around stormwater and sewer pipes so they're evenly supported and protected from rocks. Plumbing standards and your local water authority set what's acceptable.
Where you'll see it: in the trenches before they're backfilled, usually during site works and drainage.
What to check on your build
You don't need to identify sand by sight, but you can ask the right questions at the right time.
At slab stage
- Fill under the slab. Ask how deep it is and whether it's been placed and compacted in layers. Where your engineer requires it, ask for the compaction test results or certificate.
- Pipe trenches. Pipes should be bedded and surrounded in clean sand, not dumped straight on rocky spoil.
- Concrete dockets. Check the grade on the delivery docket matches the engineering. That covers the sand you can't see.
Our C5 Pre Pour Slab checklist covers fill, plumbing and pre-pour checks.
At brick stage
- Mortar ingredients. Brickies' sand, cement and lime (or a proper additive) should be on site. Our post on mortar mixes explains what the mix should be.
- Consistent colour. Patchy mortar colour across walls usually means inconsistent sand or measuring.
- Firm joints once cured. Mortar you can scrape out with a key is a problem.
- White staining (efflorescence) soon after laying can point to salts in the sand or bricks, or too much water.
The C11 Enclosed Stage checklist covers brickwork and mortar. Both checklists are at constructor.net.au/checklists.
At landscaping
Check paver bedding is a proper coarse bedding sand, screeded and compacted, over a compacted base. Pavers laid on whatever was left in the yard won't stay flat.
Natural sand and the environment
Extracting sand from rivers and coastal areas is tightly controlled because of its environmental impact. That's one reason manufactured sand and blends are now so common in concrete. Recycled crushed concrete and glass are also used in some fill and drainage applications. For homeowners, the point is simple: the sand should suit the job and meet the relevant standard, whatever its source.
The bottom line
Different jobs need different sands. Brickies' sand goes in mortar, washed and manufactured sand go in concrete, and fill sand is only as good as its compaction. Ask what's going where at slab and brick stages, and you'll avoid some of the most common and most expensive surprises.
Test yourself
Three quick questions on this topic. Click a question to see the answer.
Why is the choice of sand type crucial in construction projects?
Different sand types have unique properties affecting durability and strength.
What makes river sand particularly suitable for plastering?
Its fine, smooth texture and uniform grain size.
How does the quality of sand affect concrete strength?
Impurities in sand can weaken the concrete mix.
Anthony Painter
Anthony Painter
