How to level a garden with topsoil

Before you buy a single bag, work out what flat actually means for your garden. You almost never want it dead level. A slight fall of around 1 in 80, roughly 12mm drop per metre, lets surface water run off instead of sitting on top. Aim that fall away from the house and any walls.

Knock timber pegs in across the area and run a string line between them with a line level, or a long spirit level sat on a straight batten. That shows you the high and low points. Where you can, set your finished level off the high point so you are mostly importing soil into the dips rather than digging spoil out and carting it away.

One hard rule near buildings: keep the finished soil level at least 150mm, two brick courses, below the damp proof course. Piling soil up against the wall bridges the DPC and lets damp track into the brickwork.

The sum is simple. Area in square metres times the depth in metres gives you cubic metres. So 50 m2 at 50mm deep is 50 times 0.05, which is 2.5 m3. Topsoil weighs around 1.5 tonnes per cubic metre, so that is about 3.75 tonnes, or roughly 4 bulk bags.

As a quick check, one bulk bag is about 0.7 m3 and covers around 7 m2 at 100mm deep, or 14 m2 at 50mm. Add 10 to 15 percent to whatever you calculate, because soil packs down noticeably once you firm it.

For the top layer you are going to seed or turf, use screened topsoil. It rakes down to a fine tilth with no big stones, and TopTurf sells it at £70 a bulk bag, delivered from Leigh. If you are building up a big level change, do the deep base with cheap fill material and cap it with the screened soil where the roots will live.

Clear the area of debris, stones, old slabs and weeds, and strip any tired turf you are not keeping. Perennial weeds like couch grass and bindweed will grow straight back through fresh soil, so get the roots out now.

Then move your own soil around before importing anything. Cut the high spots down and barrow that material into the hollows. This cut and fill costs nothing and often halves how much topsoil you need to buy. Keep the good dark topsoil near the surface, and do not bury it under subsoil you have dug out.

Do not tip the whole lot on and rake it flat in one pass. Spread topsoil in layers of around 50mm and firm each layer before adding the next. Loose, unconsolidated soil is what causes a lawn to sink into dips and ripples a few weeks after you have finished.

Firm by treading the whole area with your weight on your heels, then rake, then tread again across the other direction. A half filled garden roller does the same job on larger areas. On deep fill, firm every layer, not just the top one.

Finish with a final rake to a fine, crumbly tilth and pick out any stones bigger than a £2 coin. Check your string lines one last time to confirm the fall is still running the right way.

Once the ground is firm and raked level you can turf or seed. If you have used deep fill, water it and give it a week or two to settle first, then top up any dips that appear before you lay anything on top.

For turf, order it cut to order so it arrives fresh and lay it within a day. TopTurf premium lawn turf is £4 per m2. Grass seed is cheaper but slower, and best sown in spring or autumn.

TopTurf supplies topsoil, turf and landscaping bark for your borders, all delivered from Leigh, with delivery from £20, worked out from your postcode and how much you order. If you would rather not do the grading yourself, supply-and-lay is on offer too, handled by Barrow Landscaping.

For minor levelling under new turf or seed, 25 to 50mm of screened topsoil over firm ground is usually enough. For filling dips or building up a level change you can go deeper, but firm it in 50mm layers. Turf and grass want about 100 to 150mm of decent soil to root into, so if your existing soil is poor, aim for that depth of good soil in total.

It depends on depth. At 50mm you need about 2.5 m3, which is roughly 4 bulk bags. At 100mm, double that. TopTurf screened topsoil is £70 per bulk bag. Add 10 to 15 percent because soil packs down when you firm it.

Yes, as long as the topsoil is firmed and raked level first. Loose soil sinks unevenly and you end up with a lumpy lawn. Firm it by treading, rake to a fine tilth, then lay the turf within a day so it does not dry out.

Use screened topsoil for the top layer you are going to seed or turf, as it rakes to a fine tilth with no big stones. Cheap unscreened fill, where yards sell it, is a base for deep build-ups, with screened soil capped over the top. TopTurf sells the screened grade at £70 a bulk bag.

Top dressing is for very minor bumps in an established lawn, where you brush a few millimetres of sandy soil over the grass at a time without smothering it. For anything deeper than about 25mm, use topsoil to build the level up properly and then reseed or returf the covered area.