What Is MOT Type 1? And When Should You NOT Use It?

What Exactly Is MOT Type 1 and What Is It Made Of?

• ✔ Crushed stone graded down to dust
  
  MOT Type 1 is made from crushed rock — usually granite, limestone, or recycled concrete — that ranges from roughly 40mm chunks down to fine dust. This mix helps it compact solidly.
• ✔ Packs tight and locks together
  
  The range of sizes means it knits together well when compacted. The big bits provide structure, while the fine dust fills the gaps and locks everything down into a hard, stable layer.
• ✔ MOT stands for Ministry of Transport
  
  It meets road-building standards, which means it's strong enough to go under highways — and more than tough enough for patios, driveways, garden bases, or concrete slabs.
• ✔ Ideal under paving, concrete, or slabs
  
  MOT Type 1 is the go-to choice for sub-bases. Whether you're laying block paving, pouring concrete, or prepping for a garden room, it gives you a solid foundation that won’t shift.
• ✔ It’s not pretty — but it performs
  
  You won’t win design awards with MOT Type 1, but it does exactly what you need: forms a rock-solid, long-lasting base that holds up under pressure without sinking or shifting.

Why Is MOT Type 1 Commonly Used Under Driveways and Slabs

MOT Type 1 is commonly used under driveways and slabs because it compacts well and creates a strong stable base. The mix of crushed stone and fine dust allows it to lock together tightly once compacted which helps spread the weight of whatever is built on top. That makes it ideal for supporting concrete and block paving without the risk of sinking or shifting.

It also allows water to drain through instead of pooling which helps prevent problems like frost damage or soft spots forming under the surface. MOT Type 1 meets a recognised standard so you know it is consistent and reliable. It is widely available, easy to use and suitable for most ground conditions which is why it is used on everything from domestic driveways to major roadworks.

When Should You Avoid Using MOT Type 1 Altogether?

• ✔ The ground underneath is soft, wet, or unstable
  
  On very soft or soggy ground, MOT Type 1 can sink and mix with the soil, weakening the base and causing dips or slab movement over time.
• ✔ You need a free-draining base
  
  MOT Type 1 contains fines that bind together when compacted, which is great for strength but poor for drainage. It's not ideal for soakaways or gravel paths where water needs to flow freely.
• ✔ You're laying resin bound or decorative finishes
  
  Some surface finishes require a cleaner, open-graded stone underneath. MOT Type 1 might not meet those product specs, especially if permeability or precision is needed.
• ✔ You're working in tight depth conditions
  
  MOT Type 1 needs a good thickness to compact properly. If your build-up is limited, you may need a thinner alternative that still offers load support without eating into the final slab depth.

How Thick Should MOT Type 1 Be Laid for Different Jobs

How thick MOT Type 1 should be laid depends on what you are building on top of it and how much weight it needs to handle. For light jobs like garden paths or small shed bases you can usually get away with around 75 to 100 millimetres compacted. That gives you enough strength without going overboard.

For driveways patios or anything taking regular use from vehicles you want at least 150 millimetres compacted and sometimes more if the soil underneath is soft or the ground sees a lot of use. For heavier builds or where there is poor ground you might go up to 200 or even 250 millimetres to make sure the base stays solid over time. Always lay it in layers and compact each pass properly. Do not throw it all in at once and hope the whacker plate gets through it.

Should You Always Use a Geotextile Fabric with MOT Type 1

You do not always need geotextile fabric with MOT Type 1 but it is a smart idea if the ground underneath is soft clay damp or a bit unpredictable. The fabric acts as a barrier stopping the MOT from sinking into the soil or mixing with it over time which helps the base stay level and strong. On firm well drained ground you can sometimes skip it but if there is any doubt it is better to put it in.

It also helps with drainage and keeps things from shifting about underneath the slab or blocks. It does not take long to lay and once it is down it gives that extra bit of protection that can save you problems later on. If you are not sure what the soil is like or you are working on a new bit of ground it is worth adding the fabric just to be safe.