Pick up a bag of builders sand and rub a pinch between your fingers. It should feel almost silky, with no grit catching on your skin. That softness is the whole point. Builders sand is bred for smoothness, not strength, and understanding that one fact tells you almost everything about when to use it and when to leave it on the shelf.
What Is Builders Sand?
Builders sand, also known as soft sand or bricklaying sand, is a fine, screened sand made up of small, rounded particles. It's washed and graded to remove stones, clay lumps and larger debris, which is why a good bag of it looks almost uniform in colour and texture.
The rounded grain shape is what sets it apart from sharp sand, which is coarser and made of angular particles. Rounded grains slide past each other easily when wet, which gives builders sand its smooth, buttery workability. That's brilliant for finishing a wall neatly. It's less brilliant if you need something to hold firm under a driveway, which is why the two sands aren't interchangeable no matter how similar they look in the bag.
What Is Builders Sand Used For?
Mixing Mortar for Bricklaying
This is the job builders sand was made for. Mixed with cement, usually at a ratio of around 4 or 5 parts sand to 1 part cement, it produces a mortar that spreads smoothly off the trowel and grips brick or block without slumping. Too coarse a sand here and you'll fight the mix all day, with mortar that tears rather than smooths as you point each joint.
Rendering Walls
External rendering needs the same fine, workable quality, often with a slightly richer mix and sometimes a plasticiser added to improve workability further. A render mixed with sharp sand will look lumpy and pitted once it's dried, no matter how carefully you trowel it, because those larger angular grains show through the finish.
Pointing and Finishing Joints
Whether it's brickwork or the joints on a patio, builders sand gives a neat, tight finish that doesn't look gritty once it's dry. Most repointing jobs on older Wiltshire cottages and terraces use a lime mortar mix with builders sand for exactly this reason, since the fine texture matches the softer, more forgiving look of traditional pointing.
Play Sand
Builders sand is sometimes used for filling children's sandpits, but this needs a word of caution. Standard builders sand hasn't been through the same hygiene testing as dedicated play sand, and it can be dustier and hold more moisture. If it's for a sandpit, spend the extra few pounds on a proper washed and graded play sand rather than assuming any soft sand will do.
Grades of Builders Sand
Not all builders sand is identical. It's typically supplied in a few grades depending on how finely it's been screened:
| Grade | Typical use |
| Fine, washed | Rendering, fine pointing, decorative finishes |
| Standard bricklaying grade | General mortar mixing for brick and block work |
| Bulk/unwashed | Larger backfill or levelling jobs where finish doesn't matter |
If you're not sure which grade a job needs, tell us what you're building rather than the grade you think you want. We'd rather ask a couple of questions at the counter than have you back a week later with a wall that won't trowel up properly.
Why Choose Builders Sand Over Sharp Sand?
It comes down to what the finished job needs to do. If it needs to look smooth and hold shape without bearing serious weight, builders sand wins every time. If it needs to compact hard and resist movement, like the bedding under a patio or the concrete around a fence post, sharp sand is the right call instead. Reach for builders sand on anything decorative or structural-but-light, and reach for sharp sand on anything load-bearing.
One thing we see a lot at the yard: DIYers who buy one bag of "sand" for an entire project without realising a patio and a garden wall need two different products. It's a quick fix if you catch it before mixing, and a much bigger headache if you've already laid a bed with the wrong material.
Getting the Right Sand for Your Job
If you're planning a bricklaying, rendering or pointing job anywhere around Swindon or the surrounding villages, it's worth having a rough idea of quantity before you call, even if it's just the wall dimensions or how many bricks you're laying. Browse the full range of building aggregates online, or if you're local, pop into our Swindon yard and we'll help you work out exactly what you need and how much of it.