Q: What is MOT Type 3?
MOT Type 3 is a sub-base with reduced fines to allow water to free drain as a permeable sub base.
Q: What can I use MOT Type 3 for?
MOT Type 3 is widely used as a sub-base material for projects where a higher percentage of larger sized aggregate and a lower fines content is required for improved drainage. Examples are:
- Permeable paving on driveways
- Tennis courts
- Sports pitches
- Equestrian arenas
- Tree root protection systems
- Hard standings
- Paths and patios
Q: What is the difference between MOT Type 3 and Type 1?
MOT Type 3 has less fines than MOT Type 1 making it a more appropriate solution for permeability. MOT Type 3 is ideal for SuDS (Sustainable Urban Drainage Systems). Whilst MOT Type 1 is not compliant, MOT Type 3 can be used for SuDS when creating permeable surfaces. Our Type 3 MOT complies with the Department of Transport Specification for Highway Works, clause 805 (SHW 805).
Q: Should I compact MOT Type 3?
Both the sub-base and the laying course require adequate compaction to prevent dips and undulations from appearing in your project. We reccomend using a plate compactor, or a hand tamp. We recommend that your sub-base material is compacted to a minimum of 80% of its compaction capacity.
A typical vibrating plate compactor will only achieve 80% compaction when the sub-base material is no more than 50mm thick. Therefore, you should only ever compact 50mm of aggregate at a time. So, in the case of a 100mm sub-base layer, you’ll want to compact this in two separate layers to achieve the desired result.
Q: Why should I saturate the sub-base before compacting?
Water also has an important role to play in compaction of the sub-base material. After importing and levelling your sub-base material, be it type 1, chippings, or the granite/limestone dust laying course, we recommended saturating the aggregate. By doing so, you’ll further aid the compaction of the material.
You’ll want to ensure that the water penetrates the entire depth of the sub-base material from top to bottom, but you’ll want to avoid flooding the surface. If the base is too wet, you’ll find that your plate compactor sinks too deep into surface. If this is case, allow the aggregate to dry out.