What Is Ballast in Construction?

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What Exactly Is Ballast?

  • ✔ A pre-mixed blend of sharp sand and gravel

    Ballast is a ready-made mix of coarse gravel and sharp sand, designed for making concrete. The sand fills gaps between the stones and binds well with cement, making it ideal for DIY concrete jobs.
  • ✔ Commonly used for bases, footings and general concrete

    Ballast is used for shed bases, fence posts, slabs, driveways, and small foundations. It’s strong enough for most non-structural builds and easy to work with on site.
  • ✔ Comes in 10mm or 20mm sizes

    You’ll find 10mm ballast for smoother concrete (like slabs and paths), and 20mm for heavier-duty work like footings or driveways.
  • ✔ Sold in bulk bags or loose loads

    Ballast is available from most builders’ merchants in jumbo bags, bulk loads or small 25kg bags — perfect for any scale of job.
  • ✔ Ideal for 5:1 concrete mixes

    The standard concrete mix ratio using ballast is 5 parts ballast to 1 part cement, with water added gradually until the mix is workable.

✔ How to Mix Concrete Using Ballast

  1. 1

    Measure out your mix

    The standard ratio for general concrete is 5 parts ballast to 1 part cement. Use a bucket or shovel to measure your mix evenly. For small jobs, a typical wheelbarrow load might include 5 full shovels of ballast to 1 shovel of cement. For larger batches, scale this up while keeping the ratio the same. Using pre-mixed ballast makes this easier than sourcing sand and gravel separately — just make sure your cement is dry and fresh.

  2. 2

    Add water slowly and mix thoroughly

    Once your dry mix is ready, add water gradually. Start slow — it’s easier to add more than take it out. Use a shovel, mixer or paddle to turn the mix until every part is wet and workable. The goal is a consistency that holds shape when shovelled but isn’t too stiff or sloppy. If it’s too wet, the mix will weaken and take longer to cure. Too dry, and it’ll be hard to finish and won’t bond well. Take your time — this part makes or breaks the final result.

  3. 3

    Pour and finish your concrete

    Once your mix is ready, pour it immediately into the prepared area. Spread it roughly into place using a shovel or rake, then tamp it down with a straight edge or board to level the surface. For slabs or bases, use a float or trowel to smooth the surface and push down any gravel. Concrete using ballast will begin setting in 1–2 hours depending on temperature, so don’t wait around. Finish your edges and cover the surface if rain or direct sun is expected during curing.

Ballast Types and Common Uses

Ballast Type Description Common Use
10mm Ballast Finer mix of sharp sand and smaller gravel Slabs, shed bases, garden paths — smoother concrete
20mm Ballast Coarser mix with larger aggregate Footings, driveways, heavy-duty bases — stronger mix
Pre-bagged Ballast Ready to go in 25kg or bulk bags DIY jobs, small pours, patch repairs
Loose Ballast (Bulk Load) Delivered loose from a merchant or yard Large jobs like foundations, slabs, and full bases
DIY Mix (Sand + Gravel) Combine sharp sand and gravel manually When you want more control over mix ratios

Using Pre-Mixed Ballast

  • Convenient — no need to source sand and gravel separately.
  • Great for small to medium DIY concrete jobs.
  • Consistent mix that’s ready to go with cement and water.
  • Available in bags or bulk for any scale of job.

Using Pre-Mixed Ballast

  • Less flexibility — you're stuck with the standard mix ratio.
  • May cost more than buying sharp sand and gravel separately.
  • Harder to tweak strength for specialist concrete mixes.

Mixing Your Own (Sand + Gravel)

  • More control over the ratio for specific strength needs.
  • Potentially cheaper if you're buying materials in bulk.
  • Better for large projects or customised concrete mixes.

Mixing Your Own (Sand + Gravel)

  • More time-consuming to measure and mix correctly.
  • Requires more effort, space, and sometimes more mess.
  • Easier to get the ratio wrong if you're not experienced.
🔹 What is the standard mix ratio for ballast and cement?
The most common mix ratio is 5:1 — that’s five parts ballast to one part cement. This gives a strong, general-purpose concrete suitable for footings, shed bases, paths, and slabs. You can go slightly stronger (4:1) for heavier loads or structural work.
🔹 Can I use ballast for concrete footings?
Yes — 20mm ballast mixed at a 5:1 or 4:1 ratio with cement is commonly used for footings. It’s easy to work with and strong enough for most garden or outbuilding foundations. Just make sure your trench is well-prepped and level.
🔹 Is ballast the same as MOT Type 1?
No — ballast is used to make concrete, while MOT Type 1 is a sub-base material made of crushed stone. MOT Type 1 is compacted under slabs or driveways to provide a stable base, but it doesn’t contain sand or cement.
🔹 Can I mix ballast and cement by hand?
Definitely — for small jobs, you can mix ballast and cement by hand using a shovel and a mixing tray or wheelbarrow. Just take your time, add water slowly, and mix thoroughly to get the right consistency before pouring.

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