THE QUICK ANSWER
The below guide will ensure a solid surface which will stand the test of time and hold the weight of everyday vehicles. If the purpose of the area requires it to withstand heavier traffic, HGVs for example, then a deeper layer of MOT sub-base should be used. This should be compacted in layers of 50mm. The ideal Block Paving base for a driveway would be the following:
- Geo-Textile Membrane
- 100-150mm of MOT type 1
- 40mm of Sharp Sand
- 50mm Block Paving
USING A GEO-TEXTILE MEMBRANE
Your contractor should install a Geo-textile Membrane on your project. By doing this they’re effectively preventing the sub base from dispersing into the sub-grade underneath. You can pick up non-woven Geo-textile membrane from most builders merchants. If you’re a contractor, use it! It’s worth it’s weight in gold. Not using a membrane will cause weeds to sprout through the mot, sand and eventually the gaps in-between the blocks. This will move the blocks and cause all kinds of structural issues.
The diagrams show a visual description of what we mean.
Top tips for installing the perfect base
- Geo-textile membrane – It’s surprising just how much of an impact the use of a membrane to retain the MOT has on the durability of the paving.
- Compact in layers – Studies show that by compacting the MOT in layers of a couple of inches at a time, you create a stronger surface.
- Sand perfection – Your contractor should be screeding the sand at a maximum depth of 50mm. Any more and it will weaken the finished product. Ensuring that the sand is completely level will make the installation of the blocks a lot easier.
- Use a heavy duty whacker plate – Contractors should be using a large enough whacker plate as to maximising the compaction of the MOT and sharp sand. This will increase the overall binding of the base, in turn, strengthening the final product.
BEST HARDCORE FOR BLOCK PAVING
Type 1 MOT is the preferred hardcore for the sub base of block paving. Type 1 is a blend of clean stone mixed with fines, which compacts to a solid surface when whacked. The preferred depth is around 100-150mm, depending on the existing sub-grade, how steep the area is and what it’s going to be used for.
Compact the MOT in layers to maximise the strength.
Type 3 MOT is also a popular option. We suggest the use of type 3 on a project where permeability is essential (even if you’re using permeable blocks you will still need a permeable base). Type 3 MOT is not as strong as Type 1 as there are no fines (tiny particles) which help bing the stone together when compacted.
So to summarise; Clean type 1 MOT should be used unless permeability has been specified, in which case type 3 is essential.
FINDING THE RIGHT CONTRACTOR
Finding a contractor who is keen to impress, trustworthy and reliable is not always easy. Unfortunately, there are many companies out there claiming to be block paving ‘specialists’ who end up cutting corners and rushing jobs. We are here to give you the information and advice you need to try and spot the good from the bad. We recommend using a contractor who is established, has good reviews online and is reasonably priced. We have a growing network of trusted contractors who we have vetted ourselves. Feel free to fill out one of the forms dotted across the website to receive ups to 3 quotes from our own vetted Block Paving contractors.