Can You Lay Block Paving on Top of Old Concrete?

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Got an old concrete driveway or patio and thinking about laying block paving over the top? You’re not alone — it’s one of the most common paving questions out there. The idea of skipping a full dig-out is tempting, especially if the concrete seems solid. The good news? Yes, you *can* lay block paving over existing concrete in many cases. But you’ll need to follow the right steps to avoid poor drainage, shifting blocks, or long-term issues. This guide walks you through when it’s possible, when it’s not, and how to get it right the first time.

✔ How to Lay Block Paving Over Old Concrete

  1. 1

    Clean and Inspect the Concrete Slab

    Start by giving the concrete slab a deep clean using a pressure washer. You want to remove all dirt, moss, oil, and loose debris to ensure the new paving layers bond properly. Once clean, inspect the slab closely. It should be level, structurally sound, and free from large cracks or loose sections. Hairline cracks are okay, but anything wider than 5mm could cause future movement in the blocks and may need filling or repair. If the surface is crumbling or visibly sinking, laying on top is not recommended — full removal is a safer option. Remember: your new paving is only as strong as the base underneath it.

  2. 2

    Check and Adjust Fall or Drainage if Needed

    Concrete slabs often have little or no fall — and block paving needs proper drainage. Use a long level or string line to check if the slab slopes away from the property at around 1:80 (1.25%) or more. If the fall is too flat, surface water will pool under or around your new paving. You can correct small falls with a screeded mortar bed or drainage channels, but serious issues may need you to dig out and relay. Also, make sure water doesn’t run toward doors or brickwork. If necessary, install drainage channels at key points to divert runoff away from the house. Laying blocks on concrete without managing water properly is one of the most common causes of failure later on.

  3. 3

    Lay a Bonding Layer Over the Concrete

    You can’t lay block paving straight onto bare concrete — it needs a bonding layer. You’ve got two main options: a screed mix of sharp sand and cement (dry or semi-dry), or a full mortar bed using a wet sand/cement mix. Spread the bonding layer evenly across the surface, keeping the thickness consistent — typically 30–50mm depending on the block height. For driveways, use a stronger mix (around 4:1 ratio). For patios or paths, a slightly leaner mix may do. Compact lightly with a tamper or float — don’t just sprinkle it loose. This layer creates the buffer that helps absorb movement, provides support under the blocks, and ensures better long-term stability.

  4. 4

    Place the Blocks Tightly and Evenly

    Once your bonding layer is ready, begin laying the blocks in your chosen pattern. Start from a straight edge or a string line guide and work outward, ensuring tight joints between each unit. Don’t leave wide gaps — block paving is designed to be close-fitting so the sand jointing holds firm. Tap each block down gently into the mortar or screed bed using a rubber mallet, checking levels as you go. Keep an eye on alignment, especially in herringbone or stretcher bond patterns. If you’re working on a slope, lay from the low point upward to avoid shifting. Cut blocks as needed to finish edges using a disc cutter or block splitter.

  5. 5

    Compact, Joint, and Seal the Surface

    Once all blocks are laid, sweep kiln-dried sand into the joints to lock them together. Run a plate compactor over the surface using a protective mat to avoid scuffing. This helps settle the blocks and tightens the jointing sand. Repeat the sanding and compaction until the joints are full. If drainage or weather is a concern, consider sealing the surface with a breathable, water-repellent paving sealer. It helps lock in the sand, enhances colour, and offers extra protection against moss and frost. Now your overlay is complete — and if done right, it’ll look just as good as a full dig-out job.

When You Can Lay Block Paving on Concrete

  • ✔ The concrete slab is stable and crack-free

    If the concrete is solid, level, and free from major cracks or crumbling, it can often be used as a base. Minor surface wear is fine, but large cracks or hollow-sounding spots are red flags. The paving will only be as good as what’s underneath.
  • ✔ Surface has a good fall for water runoff

    A flat slab with no fall can lead to standing water or drainage problems. You’ll need at least a 1:80 fall (1.25%) to ensure proper runoff. If the concrete already slopes away from buildings, that’s a big plus.
  • ✔ There’s no pooling or damp against buildings

    If water tends to sit near your walls or pooling happens on the surface, fix that first. Block paving over damp-prone areas will only trap moisture and cause long-term issues. Drainage must be sorted before any new layer goes on top.
  • ✔ You’re using thin blocks or block paving tiles

    For overlays, it helps to use thinner pavers or block tiles designed for this purpose. Standard 50–60mm driveway blocks can work too, but you’ll need to account for final height to avoid tripping hazards or raised levels near doors.
  • ✔ A suitable mortar or screed layer is planned

    Don’t just lay blocks onto dry sand over concrete — it won’t hold. You’ll need either a full mortar bed or a semi-dry screed to provide strength, stability, and long-term support. Skipping this step is a common reason overlays fail.

Overlaying Block Paving vs Full Dig-Out

Method Best For Pros Cons Drainage Needs
Laying Over Existing Concrete Paths, patios, stable old slabs Faster install, no digging, less mess Relies on concrete condition, harder to fix later Must have existing fall or add drainage channels
Full Dig-Out and New Sub-Base Driveways, heavy traffic, poor drainage areas Best long-term durability and water control More labour, higher cost, skips convenience Customisable fall and soakaway options
🔹 Is it okay to lay block paving directly onto concrete?
Yes, if the concrete is solid, level, and has proper drainage, you can lay block paving over it using a mortar or screed bed. Just make sure the surface is clean, free of cracks, and allows water to drain away — otherwise, you risk movement, moss, or frost damage later.
🔹 Do I need to remove the old concrete first?
Not always. If the existing concrete is sound and meets fall requirements, you can save time and money by laying over it. However, for driveways, poor drainage areas, or crumbling slabs, full removal and a fresh sub-base is the better long-term option.
🔹 Can I use sharp sand on top of concrete?
No — laying dry sharp sand directly on concrete is not recommended. It won’t bind properly and can lead to unstable blocks. You’ll need to use either a semi-dry sand/cement screed or a full mortar bed to create a secure layer that holds the paving in place.
🔹 How do I make sure water drains properly?
Check that the existing concrete has a slope (fall) of at least 1:80. If not, you’ll need to either build in a slight slope with your screed layer or add drainage channels at the lowest points. Water pooling is a major cause of long-term damage to block paving.
🔹 Will the paving last as long as if I dug it out?
It can last a long time if done properly — but it won’t be quite as durable as a full dig-out with a fresh MOT Type 1 sub-base. That said, for light-use areas like patios or paths, a concrete overlay with correct prep can last 10–15 years or more.