Screened vs unscreened topsoil

Screened topsoil is dug soil pushed through a mesh screen to take out stones, clods, roots and rubbish. The mesh size sets how fine it comes out, and 10mm is the usual general purpose grade. Unscreened topsoil, sometimes sold as economy fill or as-dug soil, goes straight from the ground into the bag with the stones, clay lumps and bits of root still in it.

Neither is better on its own. They are for different jobs. Paying premium prices to bury screened soil under a patio base is wasted money, and trying to seed a lawn into stony as-dug soil is a bad afternoon.

Use economy fill for anything you are burying or levelling in bulk: raising a low garden, backfilling behind a wall, filling the base of a raised bed, or building up levels before a proper topsoil layer goes over the top. The stones do not matter under the surface.

TopTurf does not sell an unscreened grade, but plenty of yards do, usually under names like economy fill or as-dug soil. If you are shifting a lot of volume to bring a garden up, an unscreened load for the buried layers, capped with screened soil, is the cheap way to do it.

Screened topsoil is what you want within about 100mm of the surface: under new turf, for seeding a lawn, filling planters and raised beds, or top dressing. It rakes to a flat, fine finish and you are not forever picking stones out. This is the grade TopTurf sells, at £70 a bulk bag.

Some suppliers also carry premium BS3882 grade. BS3882 is the British Standard for topsoil, so it is tested for pH, nutrients and contaminants rather than just sieved, and it shows up on high spec planting jobs like veg beds and tree pits.

For most gardens, a decent screened topsoil covers the lot. Pay for the certificate when the job genuinely calls for a tested spec, not for an everyday lawn or border.

The number, 10mm, 20mm or 6mm, is the mesh the soil was passed through. Nothing bigger than that gets through.

10mm is the standard all rounder for turf, seeding and beds. A finer 6mm suits a proper seedbed or lawn top dressing where you want a really fine tilth. Coarser 20mm still has small stones in it and sits closer to a general fill. For most gardens, 10mm is the one to ask for.

Work out your area in square metres, then pick a depth. Under turf allow 100mm to 150mm of good topsoil. For raised beds and veg fill allow 200mm to 300mm or more. Top dressing a lawn is only a few millimetres.

Topsoil weighs roughly 1.5 tonnes per cubic metre. A TopTurf bulk bag is about 0.7 m3, which covers around 7 m2 at 100mm deep or about 14 m2 at 50mm. So a 20 m2 lawn area at 100mm needs about three bulk bags.

Round up rather than down. Soil settles and compacts once it is down, and running short halfway through a job is worse than having a barrow load spare.

TopTurf is in Leigh and delivers bagged topsoil from £20, set by your postcode and the size of the order.

If the soil is going under a lawn, Barrow Landscaping can lay the turf straight onto the screened soil in one go, so you are not trying to match up two different suppliers or work out coverage twice.

You can if you break it down and rake out the worst stones first, but it is hard work and the finish is never as level. For turf and seeding, screened topsoil is worth the extra. If money is tight, put cheap fill down to build the levels, then a 50mm to 100mm layer of screened soil on top for the turf to root into.

It is topsoil certified to British Standard 3882, tested for things like pH, nutrient levels and contaminants. Some suppliers stock it for high spec planting jobs. TopTurf sells screened topsoil rather than a certified line, at £70 a bulk bag.

A bulk bag is about 0.7 cubic metres. That covers roughly 7 m2 at 100mm deep, or about 14 m2 at a 50mm top dressing depth. By weight it works out at around a tonne, since topsoil is about 1.5 tonnes per cubic metre.

Screened topsoil is fine to grow in and far easier to work than as-dug soil, but it is graded for stone content, not for nutrients. For a serious veg bed, some growers pay for BS3882 certified soil from a specialist because it is tested for what plants actually need.

Fill, or economy fill, is unscreened as-dug soil for bulking out and raising levels where the finish does not matter. Topsoil usually means the screened or certified grades you would plant or turf into. TopTurf sells the screened grade only, at £70 a bulk bag.