How to fix sinking pavers?

Will_sy2002

Hi everyone,

I’ve noticed that the pavers in my garden under my shed are sinking. They have dropped more than 5cm below the level of the adjacent concrete floor.

I’m planning to lift the affected pavers and re-level the area so it's flush with the concrete again. Could you please advise on:

1. Materials: What should I use for the base? Is a mix of compacted road base and leveling sand the best way to go, or should I use something else to prevent it from sinking again?
2. Tools: What specific tools will I need to get a professional, level finish?
3. Drainage: Should I be looking at any specific drainage solutions to stop the soil from shifting under the pavers in the future?

I've attached some photos showing the 5cm drop. Any tips on how to match the height perfectly with the concrete would be greatly appreciated!

Thanks,

William

JacobZ

Hi @Will_sy2002,

You might like to start by checking out How To Lay a Base For Pavers which shows the process from start to finish.

You're correct in terms of materials. Your best bet is to lift the pavers, put down a layer of around 100mm of road base, ensuring it is compacted well with a tamper or plate compactor, then add a layer of paver bedding sand on top, around 30mm thick, to act as a levelling medium.

Now, drainage is likely the root cause of the sinking, so it’s important to get it right. The key idea is to keep water moving away and prevent it from sitting under the pavers, which is what causes the base to weaken and sink over time.

The first thing is to make sure the finished paver surface has a slight fall away from the shed or concrete slab, around 1:60, so surface water naturally runs off instead of soaking in underneath. This fall can be created in the sand layer by setting your screed rails with a very slight slope in the direction you are hoping to direct the water.

You'll note in the video they use screed rails and a screed to set the height of the sand and then level off of the rails. Please note that you don't want the area to be perfectly level in all directions as this encourages pooling, which can lead to erosion, which is likely a good part of the reason for the sinking. You can set the screed rails in place with a slight fall in the direction you'd like water to shed, then check they are nice and level relative to each other, using a long spirit level. The key is that they are level with each other at both ends of the screed rails, but that they are both falling in the same direction.

If water tends to collect in that area, you can also improve subsurface drainage by installing agi pipe in the road base layer to redirect water away. Just make sure it has adequate fall towards a suitable drainage point.

Laying geotextile fabric under the base is also a smart move, as it prevents the underlying soil from mixing with the base and helps stop it from softening and shifting when wet.

Let me know what you think and if you have further questions, please don't hesitate to ask.

Jacob