Why Is My Block Paving Sinking? Common Causes and How to Fix It
Block paving is designed to provide a strong and durable surface, so discovering that part of your driveway has started to sink can be frustrating.
You might notice one or two blocks sitting slightly lower than the others, tyre-shaped depressions where vehicles regularly park or an entire section of the driveway beginning to dip.
While the visible problem is on the surface, sinking block paving is often caused by something happening underneath it.
Finding the cause early can prevent the affected area from becoming larger and more expensive to repair.
1. An Inadequate Sub-Base
One of the most common causes of sinking block paving is a poorly constructed sub-base.
The sub-base sits underneath the paving and distributes the weight of vehicles across the ground below. It needs to be installed at the correct depth and properly compacted before the paving is laid.
If too little sub-base material was used, or it wasn’t compacted properly during installation, movement can occur once cars regularly begin driving and parking on the surface.
Over time, this movement may create noticeable dips in the paving.
2. Poor Ground Compaction
The ground underneath the driveway also needs to be stable.
If paving is installed over soft or disturbed ground without the correct preparation, the soil underneath can gradually settle.
As the ground moves downwards, the driveway construction above it moves with it.
This can sometimes affect a small isolated area, but more extensive ground movement can cause larger sections of a driveway to become uneven.
3. Water Getting Beneath the Paving
Poor drainage can cause significant problems for paved surfaces.
If large amounts of water continually enter the layers beneath your driveway, fine material can gradually be washed away or the ground itself can become unstable.
This leaves less support underneath the paving and allows the surface to sink.
A combination of sunken paving and standing water should therefore be investigated rather than simply filling the dip with extra sand.
4. Heavy or Repeated Vehicle Loads
Driveways need to be constructed for the weight they are expected to carry.
Regular use by cars is normally straightforward for a properly constructed driveway. However, heavier vehicles such as vans, motorhomes or commercial vehicles can put substantially more pressure on the ground below.
If the original driveway construction wasn’t designed to cope with these loads, depressions can gradually form along tyre tracks or regular parking positions.
5. Damaged Drainage or Underground Services
Sometimes a localised area of sinking paving can indicate a problem further underground.
Drainage pipes, old trenches and areas where underground services have previously been installed can settle differently from undisturbed ground.
A leaking underground pipe can also affect the surrounding material.
If a deep or rapidly developing depression appears without an obvious cause, it is sensible to have the area properly inspected.
6. Edge Restraints Have Failed
The blocks in a driveway rely partly on strong edging to keep the paved area contained.
If kerbs or edge restraints begin moving, blocks near the edge can spread apart. This allows jointing material to disappear and can eventually cause the surrounding paving to move or become uneven.
This is particularly noticeable around driveway entrances and areas regularly driven over.
Can Sinking Block Paving Be Repaired?
In many cases, yes.
One of the major advantages of block paving is that individual blocks can be lifted and reused.
However, simply removing the blocks and adding more sand underneath is not always a long-term solution.
The underlying cause needs to be dealt with first.
A professional repair may involve:
- Lifting the affected paving blocks
- Removing the bedding layer
- Inspecting the ground and sub-base
- Rebuilding and compacting the affected area
- Restoring the correct levels and fall
- Relaying the paving
- Replacing jointing sand and compacting the finished surface
Once complete, a well-repaired area can blend back into the existing driveway.
Don’t Ignore Areas That Continue to Sink
A small dip might initially seem cosmetic, but sinking paving can create additional problems.
Low areas collect rainwater, which encourages moss and algae and can make the surface slippery. Uneven blocks can also become a trip hazard.
More importantly, continuing movement suggests that the underlying problem hasn’t stopped.
Dealing with a small affected section early may prevent a much larger repair later.
Block Paving Repairs in Kent
If your block paved driveway has developed dips, movement or uneven areas, Kent Drives & Patios can assess the problem and recommend the most suitable solution.
Whether a section can be repaired or the driveway requires more extensive work will depend on the condition of the sub-base, drainage and surrounding paving.
Contact us today to arrange a free site survey and discuss block paving repairs or replacement anywhere across Kent.