MOT Type 1 paving sub-base

Laying paving is a huge investment, and it’s important to get it right the first time. That’s why it’s essential to ensure all the preparation and groundwork have been done correctly. And this includes using a sub-base—a layer of material placed beneath the paving. But why is a sub-base necessary? What are its benefits? This blog post looks into the reasons behind why you should use a sub-base when laying paving, helping you make an informed decision. Read on to learn more!

What is a Sub-Base?

A sub-base is a layer of material that you place underneath your paving. It is made up of either crushed stone or specific angular gravel, and its main purpose is to provide a stable foundation for your paving. A sub-base will help to prevent the pavers from shifting or moving over time, and will also improve drainage around the paving.

The Benefits of Using a Sub-Base

Installing a sub-base is one of the most important steps in any paving project. A sub-base provides a stable foundation for your pavers, and helps to distribute weight evenly. It also prevents the pavers from shifting or settling over time.

There are many benefits to using a sub-base:

1. A sub-base helps to distribute weight evenly, preventing the pavers from shifting, sinking or settling over time.

2. A sub-base provides a stable foundation for your paving slabs, ensuring that they will last for many years to come.

3. A sub-base helps to prevent weeds and grass from growing through the pavers.

4. A sub-base can help to improve drainage around your paving area, preventing water pooling and flooding.


What Happens when a Sub-Base is Not Used

If you choose not to use a sub-base when laying paving, you run the risk of the paving shifting and settling over time. This can lead to cracking, chipping, and overall damage to the paving. The paving slabs will gradually lift in some places causing trip hazards. Furthermore, where larger gaps emerge between the stones, these will be pronone to weed growth. In addition, without a sub-base, water can pool on top of the paving and cause even further damage.

Ultimately, if you do not use a sub-base at all or, in fact, if you use the wrong type of sub-base, you will need to replace your patio within a short period of time. 

In many cases, contractors will skimp on sub-base when laying a driveway for example. How often have you seen block paving driveways with sunken areas, especially under vehcile weight - this has been caused by the wrong type of sub-base or a shortcut on the quantity actually needed to undertake the job properly. 


The Different Types of Sub-Bases

There are three different types of sub-bases that are commonly used when laying paving: hardcore, sand blinding and MOT Type 1.

Hardcore is the most commonly used type of sub-base and is made up of broken bricks, concrete or stone. It is important to make sure that the hardcore used is well compacted to provide a stable base for the paving.

Sand blinding is a less common type of sub-base and is made up of a fine layer of sand. It is often used in conjunction with hardcore to provide a level surface for the paving.

MOT Type 1 is a crushed limestone, concrete or granite that contains no fines. It is the highest quality sub-base available and provides an excellent base for paving.

Let us explore the different types of sub-base commonly used and explain why some of the most popular products should never be used under your patio. 




Example of MOT Type 1

Example of MOT Type 1

Wrong Types of Sub-Base

If you're planning on laying paving in your garden or driveway, it's important to use a sub-base. This will help to support the paving and prevent it from moving or sinking over time. However, not all sub-bases are created equal, and using the wrong type can actually do more harm than good.

One of the most common mistakes is using sand as a sub-base. While sand may seem like an ideal material, it's actually quite unstable and can easily shift under the weight of the paving. This can cause the paving to sink, crack or break over time. When laying driveway block paving, it's usual for this to be laid on sharp sand, however the critical point is that this is laid on top of an MOT Type 1 sub-base. It's best practice for the sub-base to be constructed at 150mm depth aftercompacting. 

Another common mistake is using topsoil as a sub-base. Topsoil is too soft and loose to provide adequate support for paving, and will eventually lead to sinking and movement. With movement of paving slabs comes trip hazards, broken joints and weed growth. 

Cheaper materials such as crushed hardcore are often used, however these are often seen to contain a wide range of materials that will not compact down to create a firm bonded base. Much of this material is recycled from building sites and when inspected, can contain rubbish, broken glass and non-angular stone. When compacted, this will continue to move and not perform as required. 

The best type of sub-base to use is crushed stone certified and guaranteed as MOT Type 1. This material is strong and stable, making it ideal for supporting paving. It also drains well, which helps to prevent water pooling beneath the paving. As it is approved by the Ministry of Tranport (DTP1 = Department of Transport as a more current term), it means it has been tested to withstand extremes of temperature and both wet and dry conditions - as the same suggests, it's tested for use as part of the construction of roadways. It's an angular material designed to lock together when compacted and provides a stable base for your patio. Often made from crushed limestone, granite or even concrete, it is a specially made product conforming to strict standards and is not the same as 'hardcore'.


Inconsistent pieces in non MOT Type 1 product

Recycled materials are often contained in non MOT Type 1 products

How to Install a Sub-Base

If you are planning on laying paving in your garden, driveway or patio, then you will need to create a sub-base. This is a layer of material that sits underneath the paving and provides a stable foundation.

You will need to dig out an area that is slightly larger than the paving you are going to lay. The depth of the hole will depend on the thickness of the sub-base layer you want to create and the thickness of your paving slabs. As a rough guide, for a domestic patio, you will want a finished 'compacted' thickness of MOT Type 1 at 100mm and for domestic driveway paving, 150mm. Combine this with the mortar bed layer (or sand for block paving) allowing around 50mm for this, plus the thickness of your paving slabs and you then have the required depth to dig to.  

Once you have dug out the area, spread a layer of MOT Type 1 over it and compact it down using a wacka plate. Gradually build up the layers of MOT Type 1 and again compact it. Continue adding and compacting layers until you have reached the desired thickness.

When installing a sub-base, it is important to make sure that it slopes away from any buildings. This will help to prevent water from pooling on top of the paving and causing problems later on. Plan the direction any suface water needs to run and create a very gentle slope in this direction away from the property. 


We hope that this article has provided you with the information necessary to understand why using a sub-base when laying paving is so important. Not only does it help prevent future problems like weed growth, cracking and subsidence but it also creates an even base for your paving slabs to be laid on. With the right preparation, you can ensure a long-lasting and reliable foundation for whatever type of paving project you are looking to undertake. It is important to note that some contractors will cut corners on MOT Type 1 when quoting for a job, so be sure to check on this before and during work. The key to a long lasting patio is built on the foundations used, so always use the correct materials and don't skimp on quantity if you want lasting results.

Thanks for taking the time to read, we wish you all the best with your upcoming project!