How a Plate Compactor Helps You Build a Solid Base
A plate compactor (also called a wacker plate) is essential for compacting sub-base materials like MOT Type 1, crushed stone, and hardcore. Without proper compaction, your patio, driveway, or concrete base will settle, shift, or crack over time.
This guide explains how to use a plate compactor properly — including how thick to lay each layer, how many passes to do, and how to avoid common mistakes that weaken your foundation. Whether you're prepping for slabs or concrete, getting the base right is the key to a job that lasts.
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Trying to Compact Too Much in One Go
Sub-base material should be added in layers (usually 50–75mm thick). If you try to compact a full 150mm depth at once, only the top will settle — the bottom stays loose.
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Skipping Edges and Corners
These areas often get overlooked, but if they’re not compacted properly, they’re the first to shift or sink under pressure.
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Not Overlapping Passes
You should cover the whole area in overlapping lines — like mowing a lawn. Leaving gaps between passes leads to soft spots and uneven settling.
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Running It Too Fast
Go slow and steady. The machine needs time to vibrate and settle the aggregate with each pass. Rushing just bounces across the surface.
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Compacting When It’s Too Wet
Overly wet material will just smear and slide under the plate — you won’t get any real compaction. Slightly damp is best.
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Lay Your First Layer of MOT Type 1 or Hardcore
Start by spreading your sub-base material in a level, even layer. Keep it to around 50–75mm thick — this helps ensure each pass of the compactor actually compresses the full depth. Rake it out as level as possible before turning the machine on.
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Make Slow, Overlapping Passes With the Plate
Fire up the compactor and walk it slowly in straight lines, overlapping each pass by around 30%. Cover the entire area at least 2–4 times. Work in rows, then go again at a 90° angle if possible for best compaction.
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Repeat in Layers Until You Reach Your Target Depth
Once the first layer is firm and doesn't shift underfoot, add the next layer of material. Repeat the compaction process until you’ve built up to your full required depth (e.g. 100mm for patios, 150mm+ for driveways).
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Check for Soft Spots and Re-Compact
Walk the area after compacting. If you feel any soft or springy patches underfoot, go over them again with the plate. Pay extra attention to corners, edges, and trench sections — these are common failure points if missed.
- Cheaper short-term cost (usually £25–£40/day)
- Ideal for one-off patio or driveway projects
- No maintenance or storage needed
- Ongoing cost if you need it more than a few times
- May not always be available during peak seasons
- Daily hire cost can add up on larger jobs
- Better value if used on multiple projects
- You get familiar with the machine and performance
- Great for trades, landscapers, or frequent DIYers
- Initial cost is £250–£500 for a decent unit
- Needs storage space and occasional maintenance
- Overkill for small one-off jobs
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How many passes should I make with a plate compactor?
Aim for at least 2–4 full passes over each layer of material, overlapping as you go. For high-load areas like driveways, 4–6 passes gives better compaction.
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What’s the maximum depth I can compact at once?
Don’t try to compact more than 75mm at a time. Most wacker plates can’t reach deeper than that — anything thicker should be built up in layers.
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Can I use a plate compactor on soil?
Yes, but only if the soil is dry and granular. Wet or clay-heavy soil will need to dry out first or be stabilised before you get a good compaction result.