Fill Dirt: The Rough Grade, Not the Growing Layer

The low corner behind a camp that holds water into June does not want loam, and filling it with loam is how a cheap problem becomes an expensive one. Loam is the growing layer, priced and screened for what will be planted in it, and burying eight yards of it under a regraded slope wastes all of that.

Fill dirt is the other order. Screened to take out the large rocks, roots and debris, with minimal organic matter in it, meant to be compacted and buried. Two materials, two jobs, and on most sites you need both in the right order.

The low corner, the backfilled hole and the shoulder that keeps sliding

Three jobs bring most of it onto a property here.

Raising a low area. A corner of the yard where water gathers, or a soft patch beside a camp road. Fill changes the shape so runoff leaves instead of standing, which on ground that thaws from the top down in spring is most of the battle.

Backfilling an excavation. Around a foundation, against a wall, or closing out a hole where something used to be. Material with organic matter in it rots down and the grade drops, taking the slope away from the building with it. Low-organic fill does not do that.

Rebuilding a shoulder. The edge of a lane that slumps a little more each mud season, until the gravel is spilling over it and the ditch has filled in.

What all three share: the material ends up under something else. Nothing grows in it and nothing is meant to.

How fill dirt behaves on till, on ledge and on valley sand

Stony glacial till is the common subgrade here, and it holds water. Fill placed on saturated till in April will not compact, because water in the layer below has nowhere to go. It sits, then it moves.

Where granite ledge is close to the surface you are working in shallow ground. There is often no room to dig out and replace, so the fill goes on top and the finished grade rises. Plan drainage for the new shape rather than the old one, since water will now run where the fill sends it.

On sandier outwash along the Merrimack valley the subgrade drains and compaction goes quickly, but the ground gives up its shape more readily at an edge. Slope the face of any fill gently rather than trying to hold a near-vertical face with earth.

Through winter the ground is frozen and nothing can be compacted. The season for this work runs from the end of mud season to the fall freeze.

Shape the drainage first, then fill to it in lifts

Set out where the water is going before the first load lands. Fill is easy to place and expensive to move twice.

Then build in lifts. Six to eight inches at a time, compacted before the next one goes on, rather than one deep pour that looks finished and settles for three years. A plate compactor handles a small backfill; a jumping jack suits a narrow trench; a ride-on roller earns its rental on a large area.

Moisture decides the result. Fill dirt that is too dry will not knit and fill that is soaking will pump under the plate. Damp enough to hold a shape when you squeeze it, and crumble when you drop it, is the working condition.

Expect settlement. Order somewhat more than the calculated volume and plan to top up once, after a winter has had a go at it.

Loam and garden soil do the jobs fill dirt cannot

Three loads people order as fill dirt that should be something else.

A flagstone walkway. If the route dips, fill dirt brings the low stretch up to rough grade first, compacted, and that part is genuinely a fill job. What goes on top of it is not: the walk wants a compacted crushed gravel base with stone dust as the setting course under the stone.

Raised vegetable beds. Never fill dirt. It has had the organic matter taken out of it deliberately, which is the opposite of what a bed needs. Use this instead: garden soil, which is blended for planting.

A playground surface. Fill dirt can form the shape underneath if the area needs raising, but the surface is a separate order. Use this instead: shredded mulch for the play surface itself.

And where a lawn is going in, fill dirt gets you to within a few inches of finished grade, then screened loam goes over the top as the growing layer. Grass on bare fill is a thin, hungry lawn.

Yards for a low corner and a sunken stretch of walk route

Two hypothetical jobs. Dry fill dirt runs about 2,400 lb per cubic yard on this site's published figures, near enough to 1.20 tons per cubic yard. Wet, the same material can reach 3,000 lb per yard, so a load delivered after rain weighs more for the same volume.

Low corner of a yard, 18 ft by 14 ft, 8 inches of average fill

• 18 x 14 = 252 sq ft
• 252 x 8 / 12 = 168 cu ft
• 168 / 27 = 6.22 cu yd
• 6.22 x 1.20 = 7.46 tons

Sunken stretch of a walk route, 16 ft by 4 ft, 6 inches to rough grade

• 16 x 4 = 64 sq ft
• 64 x 6 / 12 = 32 cu ft
• 32 / 27 = 1.19 cu yd
• 1.19 x 1.20 = 1.43 tons

Both figures are the finished volume. Fill placed loose and compacted takes up less room than it did on the truck, so order above the calculation and keep what is left for the top-up. Other shapes go through the dirt calculator.

Where a heavy load can be tipped without wrecking the lawn

Dirt lands heavy and stays where it lands. Pick the spot with that in mind: firm ground, close to the work, off the septic field and off anything you would mind rutting.

A tarp under the pile keeps the lawn alive and makes the last wheelbarrow-load easier to collect. If the lane is still soft from the thaw, wait two weeks rather than leaving a set of ruts you will be filling next year.

Work out the volume, add for settlement, then choose a quantity and a delivery date on this page. Delivery is arranged at checkout by ZIP code, and the driver needs clear access to the spot you have picked.