Most people underestimate how much the materials side of a build project matters until something goes wrong. You’ve planned the patio, sorted the contractor, maybe even picked the pointing colour, and then someone asks how much ballast you actually need and suddenly the whole thing stalls. Getting aggregate delivered in the right quantity, in a practical format, isn’t glamorous but it does dictate how smoothly a job runs.
Ballast, for anyone not deep in the building trade, is the mixed aggregate, sharp sand and gravel combined, that goes into concrete mixes for everything from footings to garden bases. It’s workhorses stuff. Nobody’s posting about it on Instagram but without it your fence post doesn’t stand, your shed base cracks, and your driveway’s a non-starter.
The Case for Buying in Bulk
Small bags from a DIY shed are fine if you’re filling a single hole. But once you’re laying anything over a few square metres, the maths shifts dramatically. Carrying twenty 25kg bags from the car to the back garden is genuinely exhausting, and you’ll likely still run short halfway through. Bulk bags, the big one-tonne woven polypropylene kind that arrive on a pallet, make much more sense once a job reaches a certain scale.
The cost per tonne drops considerably when you buy in bulk format rather than small sacks. That’s not a controversial claim, it’s just basic supply chain reality. And you’re reducing plastic waste too, since one large bag replaces forty or fifty smaller ones. Frankly it’s a better solution on almost every front once you’re past a certain volume threshold.
That said, storage is a genuine consideration. A bulk bag takes up space, and if you leave ballast exposed to heavy rain for weeks it can affect workability. A decent tarpaulin helps, or a covered area if you have one. Not a dealbreaker, just worth factoring in before delivery day.
What to Actually Look For
Not all ballast is the same, and this catches a lot of people out. The grading matters, particularly if you’re making structural concrete rather than mixing something for a garden wall. BS EN 12620 compliant aggregate is what you want for anything load-bearing, and reputable suppliers will specify this. If the listing doesn’t mention it and you can’t find the spec on request, that’s a red flag.
Moisture content is another thing worth checking. Dry ballast is easier to work with and you get more consistent mixes, whereas wet aggregate from a supplier who stores it badly means you’re guessing your water ratios. It sounds fussy but it actually affects the finished concrete quite a bit.
For self-builders and contractors in the UK, ballast jumbo bags are widely available through trade builders’ merchants online, often with next-day pallet delivery if you order early enough in the day. It’s a good idea to compare delivery charges, as some suppliers fold it into the product price but some charge separately; depending on your postcode, that difference could be £30 or more.
How to Calculate What You Need
This is where often where people go wrong. You need roughly 6 parts ballast to 1 part cement, for a basic concrete mix. Work out the volume of concrete required in cubic metres, and multiply it by around 1.75 tonnes to figure out how much ballast you need. Many people order slightly short and then have to wait for a more, which delays everything, but if you order a little over, and you’ve got material left for the next small job rather than starting again from scratch. It’s genuinely better to have surplus ballast sitting in a corner of the garden than to grind to a halt on day two.
None of this is particularly technical once you’ve done it once. The first time is where people tie themselves in knots, usually by leaving the materials planning too late or assuming they’ll be fine with small bags. Sorting the aggregate side of a project before anything else goes up is just good practice, and it saves the kind of stress nobody needs mid-build.
