Choosing the right sub-base material can make or break a groundworks project, and it’s one of the most common questions our team here at NWTH gets asked by contractors and self-builders across Cheshire. MOT Type 1 and MOT Type 3 look similar on paper, but they behave very differently once compacted, and picking the wrong one can lead to drainage problems, settlement or a sub-base that simply doesn’t perform.
MOT Type 1 is a crushed limestone or granite aggregate that includes a mix of particle sizes down to dust. Those fines fill the gaps between the larger stones, creating a dense, tightly packed layer once compacted. It’s the standard choice for driveways, roads, car parks and patios, anywhere that needs a firm, load-bearing sub-base.
MOT Type 3 is also crushed stone, but with the fine particles largely screened out. Without dust clogging the gaps, water passes through the layer rather than sitting on top of it. Type 3 is built for permeable applications, particularly Sustainable Drainage Systems (SuDS), where managing surface water is part of the planning requirement rather than an afterthought.
The key difference:
- Type 1 is fully graded, including fines, and compacts into a dense, low-permeability layer
- Type 3 has the fines removed, so it drains freely and stays permeable under load
Type 1 gives you strength and stability. Type 3 gives you strength with drainage.
Type 1 suits standard sub-bases: driveways, footpaths, patios and trench backfill where drainage isn’t a specific requirement. Type 3 comes into its own where planning conditions demand it, such as permeable paving, soakaways and SuDS-compliant driveways, since local authorities increasingly expect developments to manage their own surface water.
Using Type 1 where drainage was specified can leave standing water and a sub-base that fails a SuDS inspection. Using Type 3 where strength was the priority can leave the layer less stable under heavy traffic. Check the specification before ordering, since the wrong sub-base is expensive to correct once it’s down.
NWTH supplies both MOT Type 1 and MOT Type 3 in bulk across Cheshire and Staffordshire, with next-day delivery. Browse our full range of quarry aggregates or get in touch to talk through your specification. Call 01606 663816, email transport@nwth.co.uk, or visit our contact page and we’ll get the right material to site on time.