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.
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.
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.
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.
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!