How to Choose the Right Sub-Base Type

Whether you are creating a patio, driveway or any other type of paving, adding the right sub-base is essential. A sub-base is the layer below the base layer that usually consists of crushed aggregates or recycled aggregates. This extra layer provides strength and support to the overlying surface. Plus, it helps to spread the load evenly over the subgrade. Best practice: Between the sub-base layer and the sub-grade layer, it is recommended to add a geotextile membrane to act as a separation layer. Types of sub-bases. The most common types of aggregate sub-bases include MOT Type 1, also known as Type 1 DOT, and MOT Type 3, also referred to as DOT Type 3. These are both crushed stone sub-bases. Type 1 MOT MOT Type 1 consists generally of crushed granite, limestone, gritstone or basalt. This sub-base is crushed to 40mm down to dust, creating small particles easy to compact. MOT Type 1 is often used for high traffic areas, such as highways, car parks and building bases, as it features excellent load-bearing qualities. Type 3 MOT Type 3 MOT consists of pure crushed limestone, granite or basalt. This sub-base might be 75mm or 40mm down depending on the location it is quarried. MOT Type 3 is most commonly used in areas where reduced fines are required to reduce drain blockages, including sub-bases for equestrian areas and sports pitches. What does MOT and DOT mean? When speaking about aggregates, MOT refers to the Ministry of Transport (MOT) and DOT refers to the Department of Transport (DOT). All aggregates sold with these acronyms are approved to be used in the construction of pavements and highways. In order for a product to be classed as 'Type 1' or ‘Type 3’ quality it must comply with the Department of Transport Specification for Highway Works, clause 803 (SHW 803) or clause 805 (SHW 805), respectively. We recommend choosing one of these certified sub-bases for your project. Having a high-quality sub-base will be a step forward setting a great foundation for your project. So, a certified sub-base will be a good choice. At Mainland Aggregates, we also supply other sub-bases, including recycled sub-bases and quarried sub base aggregates. For more information about our products, contact us today.