Why Does Topsoil Settle After Laying?

You order a couple of cubic metres of topsoil, spread it perfectly level, and a few weeks later the bed sits a centimetre or two low. Nothing's gone wrong — soil settles. Freshly dug, screened and tipped soil is full of air, and once rain, watering and plain gravity get to work the particles pack tighter and the volume drops. Here's how much to expect, and how to make sure your levels end up where you planned them — not a notch below.

How much does topsoil settle?

As a rule of thumb, screened topsoil loses about 10–15% of its loose volume over the first few months: spread 1,000 litres and you'll end up with roughly 850–900 litres of finished depth. In real terms, a bed you filled to a neat 10cm can quietly become 8.5–9cm. Freshly dug or fluffed-up soil settles hardest — up to a fifth — while sandy mixes move least. And it's not just soil: bark mulch beds down by about 10% as it settles and starts to rot, and gravel works about 10% of itself into the layer beneath.

When settling matters most

A little settling goes unnoticed on an open border, but it shows wherever there's a reference point. Raised beds are the classic case: the timber lip you filled so proudly is poking out of the soil within a month. Lawn prep is the other — a levelled area that sinks unevenly leaves dips that puddle in winter and scalp every time you mow. And the deeper the fill, the more it moves: a 30cm bed fill keeps creeping downwards for a whole season.

How to allow for it

The simplest answer is to order the extra up front: add 15% for topsoil, 10% for mulch or gravel, and settling becomes a non-event — the surface drops to your planned level instead of below it. Our topsoil, mulch and gravel calculators have an 'Allow for settling' tick-box, on by default, that does the maths for you. Filling deep? Spread in 10cm layers and water each one in as you go — you'll squeeze out most of the air before a single plant goes in.

Before you turf or plant

Give fresh soil a fortnight to make its move if you can — one good downpour or a thorough watering does most of the settling for you. Then rake level, top up any dips and firm lightly underfoot or with the back of a rake. Lightly is the key word: you're closing up the big air pockets, not ramming the life out of it — roots and new turf both need air and drainage to establish.