The Quick Answer
Yes, Block paving CAN sink, the real question is will your Block Paved driveway end up sinking? Providing the installation has been carried out by a genuine contractor who’s in it for the long run, your driveway should stand the test of time and should not start to sink.
Block paving has been around thousands of years so it stands to reason that there would be a lot of competition. This high saturation of Block Paving contractors has caused prices to reduce. This is obviously good news for homeowners like yourself, however you do need to be extra careful when choosing your contractor. With increased popularity comes increased rogue trading. Sometimes the reduction in industry prices will mean a reduction in quality of workmanship as some contractors cut corners in order to match the lower end of the pricing scale.
3 TOP CAUSES OF BLOCK PAVING DISTURBANCES
- Shallow Base – Insufficient base material is the top reason for sinking in Block Paving. There are too many contractors using either the incorrect base build up, or not enough base material to support a vehicle over time.
- Loose Blocks – A loose bond in the blocks can be formed by edges coming loose. Loose bonds cause dips over time as the blocks are continuously driven over, causing the corners of the blocks to dig into the base and gradually disturb the base.
- Ground Subsidence – Underground movements such as; low density soil settling or natural voids collapsing, can cause dips in block paving and should be investigated to understand the severity
This is a far more uncommon and completely unavoidable cause of Block Paving disturbance. The most common reason for ground subsidence is a lack of moisture in the sub grade which causes cavities to open up, eventually resulting in collapsing material. Ground Subsidence often goes undetected.
Groundwater pumping is often the cause of ground subsidence, as well as radical changes in the weather such as heatwaves.
Another way some contractors cut corners is by installing an insufficient base, or use cheap material as an alternative.
By using recycled MOT the contractor would save around £15 per tonne. Recycled MOT is built up of all sorts of materials and unfortunately some of these decompose rapidly causing voids below the surface.
Some unreliable contractors will also try and skimp on the amount of MOT they use. They will order just enough to cover the surface so it looks well prepared to the untrained eye. This shallow scattering will not hold up and will soon begin to cause movement which will resul in dips. Check out our recommended base here.
All reliable contractors should use Geo-Textile Membrane in the ground preparation. Geo-Textile Membrane is a permeable product used to separate the sub-base and the base material. The woven material helps prevent contamination of the base layer as well as keeping the base layer from falling downwards. Some contractors will leave this out of their groundworks preparation to save money. This will cause serious issues over time.
Check out our diagrams below for a better understanding of how this works:
With Geo-Textile Membrane
Without Geo-textile Membrane
If the edging isn’t cemented in correctly and loosens, the whole driveway can be effected. Think of it like a dam, the edging kerbs/ blocks are the walls and the rest of the blocks are the water. If there is a hole in the wall, the water will come pouring out. Sure, it’s not going to be as drastic as 1,000,000’s of litres of water pouring out destroying villages, but it will eventually cause disturbance of the blocks. This is a very common reason for block disturbance and can easily be avoided by ensuring the edging kerbs/blocks are installed correctly.
Tree roots are among the most common reasons for damaging block paving. Instead of dips, they more commonly cause humps and bumps. Remedial work can be done by lifting up the effected area, removing the tree root, re-compacting the area and re-laying the blocks.