Topsoil vs Fill Dirt vs Garden Soil: Which Do You Need?

If anything is going to grow in it — grass, shrubs, vegetables — the top layer should be topsoil. Fill dirt is for raising grade, backfilling and filling holes where nothing needs to grow. Garden soil or a blended mix is topsoil with extra organic matter for heavy-feeding plants.

Fill dirt is subsoil: the clay, sand and rock that sits below the growing layer. It has little organic matter, compacts well and is stable, which is exactly what you want under a patio, behind a retaining wall or when building up a low area.

It is a poor growing medium. Grass seeded straight onto fill dirt struggles to root, dries out in summer and puddles in winter.

Topsoil is the upper, organic-rich layer of soil. Screened topsoil has been run through a screen to remove rocks, roots and clumps — ours is screened to 3/8" — so it spreads evenly and seeds well.

Use it for new lawns, topdressing existing lawns, filling garden and raised beds, and as the final 4–6 inches over any fill.

• New lawn (seed or sod): 4–6" of topsoil over loosened native soil.
• Topdressing or overseeding a lawn: ¼–½" of screened topsoil raked in.
• Levelling low spots in a lawn: topsoil, added in layers of 1–2" so the grass grows through.
• Garden beds: 6–8" of topsoil; mix in compost for vegetables.
• Raised beds: topsoil blended with compost, filled to the top.
• Raising grade by more than a few inches, backfilling walls or foundations: fill dirt, finished with topsoil on top.

Much of Surrey, Langley and Cloverdale sits on heavy clay that stays waterlogged from November to March and bakes hard in August. A proper depth of screened topsoil over that clay gives roots a layer that drains and holds moisture — the difference between a lawn that thins out every summer and one that doesn't.