What is block paving used for?
Block paving is used for driveways, pavements, patios, town centres, pedestrian precincts and, increasingly, road surfacing.
The system suits any hardstanding that takes repeated loading, because the surface is made of many small units rather than one large slab. When part of the surface is damaged or the ground beneath needs attention, the affected blocks are lifted, the work is carried out, and the same blocks are relaid. Once relaid, no lasting mark remains.
The main benefit of bricks over other materials is that individual bricks can later be lifted up and replaced. Where remedial work under a poured surface such as concrete or asphalt leaves a permanent patch, the affected bricks are lifted out, the work is carried out beneath them, and the same bricks are relaid.
What are block paving bricks made from?
Block paving bricks are typically made from concrete or clay, with composite materials also in use, and the biggest difference between them is the way each one sets hard.
A clay brick is fired in a kiln, and the firing bakes the brick hard. A concrete brick is not fired; it is left to set, and the cement within the mix cures the block to full strength over time.
Concrete paving bricks are a porous form of brick formed by mixing small stone hardcore, dyes, cement, sand and other materials in varying amounts. Changing the proportions changes the block's strength, colour and texture, which is why concrete blocks come in such a wide range of finishes.
Modern manufacturing methods increasingly allow recycled materials into the mix, including crushed glass and crushed old building rubble, which reduces the volume of new raw material each block requires.
| Property | Concrete block | Clay block |
|---|
| How it hardens | Sets as the cement cures | Fired hard in a kiln |
| Colour | Added dyes; wide range of colours | Natural clay tones that hold their colour |
| Surface | Porous | Dense and low-porosity |
| Typical use | Domestic driveways and patios | Decorative areas and heritage schemes |
Which block paving laying patterns are used?
The most common block paving pattern is herringbone, because it gives the strongest bond, with stretcher bond and basketweave used where loading is lighter.
A laying pattern is not just decorative. The pattern determines how well the blocks interlock, and interlock is what spreads the weight of a vehicle across the surface instead of letting one block carry it alone.
- Herringbone: the strongest block paving bond because it offers the most interlock, making it the standard choice for driveways and road surfacing. The blocks are set at either 45 degrees or 90 degrees to the perpendicular
- Stretcher bond: blocks laid in offset rows, a simple running pattern suited to paths and lighter-duty areas
- Basketweave: pairs of blocks laid at right angles to each other in a woven effect. The bond is weaker, so it is better suited to paved areas that receive light foot traffic only
For any surface that will carry vehicles, herringbone at 45 or 90 degrees is the pattern that gives the most interlock and the longest service life.
How is a block paved surface constructed?
A block paved surface is built in layers: excavation, a compacted sub-base, a laying course, the blocks themselves, and kiln-dried jointing sand vibrated into the joints.
Excavation
[1]The area is dug out to formation level, deep enough to take the sub-base, laying course and block thickness while finishing at the required height.
Sub-base
[2]A crushed stone sub-base is laid and compacted in layers. The sub-base carries the load, so its depth decides how well the finished surface resists sinking and rutting.
Edge restraints
[3]Edges are set in concrete before the field is laid. Without a firm edge restraint, blocks creep outwards under traffic and the pattern opens up.
Laying course
[4]A screeded bed of sharp or crushed material gives the blocks a level seat. A commonly used base is cracker dust, also known as crushed bluemetal, which compacts harder than yellow brickies sand and so resists weeds and ants coming up through the joints.
Laying the blocks
[5]Blocks are laid in the chosen pattern, working from a fixed edge, with cut blocks fitted at the boundaries.
Compaction and jointing
[6]The surface is compacted with a plate vibrator and kiln-dried sand is brushed into the joints. The jointing sand locks the blocks together and completes the interlock.
Why can block paving be repaired invisibly?
Block paving can be repaired invisibly because the surface is made of individual blocks that are lifted and relaid, rather than a continuous slab that has to be cut and patched.
When a utility pipe or cable under the surface needs work, the blocks above it come up intact, the excavation is backfilled and compacted, and the same blocks go back down in the original pattern. Poured surfaces cannot do this: any cut through concrete or asphalt remains visible for the life of the surface.
The same principle covers localised settlement. If one area dips, only that area is lifted, the base is topped up and recompacted, and the blocks are relaid level.
