Guide för Bärlager

31 Jul 2026

Almost every surface failure we get asked about is a sub-base failure wearing a disguise. The grid did not fail, the gravel did not fail: the layer underneath moved, and everything above it moved with it.

A sub-base does two jobs. It spreads concentrated wheel loads across a wider area of subsoil, and it provides a free-draining layer so water moves down and away rather than sitting under the surface. Getting the depth and the compaction right is what makes both of those happen.

Step by step

How to install it

Choose your depth by use, not by habit
Footpaths and shed bases need around 50mm. Cars and light vans need 80mm to 100mm. Delivery vehicles and HGVs need 150mm. Tractors and loaded trailers need 200mm or more. If you are between two figures, take the deeper one: the extra stone is cheap compared with lifting a failed surface.
Assess the ground you are building on
Depth guidance assumes reasonable subsoil. On soft clay, peat or made ground, increase the depth and consider a geogrid as well as a geotextile. If you can push a steel bar into the formation by hand, the ground is telling you something.
Always separate with a geotextile
A woven geotextile between subsoil and sub-base stops the two mixing. Without it, stone migrates down and fines migrate up until you no longer have a sub-base, you have a layer of stony mud. Lap joins by 300mm and turn the edges up.
Use the right material
MOT Type 1 is the default: a graded crushed stone with a range of particle sizes that locks together when compacted. Clean single-size stone will not compact and will not lock. Recycled crushed concrete works well if it is clean and well graded.
Compact in layers
This is where most jobs go wrong. Lay in layers of no more than 75mm and compact each one fully with a vibrating plate before adding the next. A single 150mm pass leaves the bottom half loose, and it will consolidate later under traffic, which is exactly when you do not want it to.
Water lightly if the stone is dry
Type 1 compacts best slightly damp. Bone dry stone will not bind, and saturated stone pumps rather than compacts. A light watering between passes in dry weather makes a noticeable difference.
Check it before you go on
Walk the whole area. It should feel uniformly firm with no springy patches, and the plate should stop making progress rather than continuing to sink. Any soft area found now costs minutes; found later it costs the whole surface.
Blind before laying
Finish with a thin screeded layer of grit sand. It fills the surface voids, gives you a flat plane to lay onto, and makes the finished levels far easier to control.

Before you order

Work out your quantities

Use the sub-base calculator to work out how much MOT Type 1 to order, including the compaction allowance.

Open the calculator

Vanliga frågor

Can I use scalpings or crusher run instead?

Often yes, provided the grading is similar to Type 1 and the material is clean. Ask your supplier what the grading is rather than going by the name, which varies by region and quarry.

Do I need a sub-base at all on firm ground?

For foot traffic on genuinely firm, free-draining ground you can sometimes lay onto a prepared and compacted formation. For anything carrying vehicles, build the sub-base.

How do I know when it is compacted enough?

When the plate stops visibly settling the material and starts riding on the surface. As a rule of thumb, three to four passes per layer with a decent plate.

What about drainage falls?

A permeable surface over a free-draining sub-base does not need a fall for surface water. You may still want a slight fall away from buildings, and you should always check where the water ultimately goes.

Can I hire a plate compactor?

Yes, and you should. A garden roller or driving over it with a vehicle does not compact a sub-base. Hire is inexpensive next to the cost of the job.

Guide för Bärlager

How to install it

Work out your quantities

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