Screened Loam and Top Soil for New Hampshire Lawns

There are two windows a year for putting soil down in this state and getting grass out of it. Late August into September is the better one, when the ground is warm, the nights have cooled and the weeds have slowed. Spring is the other, once the frost is out and the ground has drained enough to walk on without leaving prints.

Miss both and you are spreading top soil onto ground that is either frozen or baking. It will still sit there. It will not grow much.

Locally this material is called loam, and most people buy it screened.

Screened top soil: what comes off the screen, and what does not

Screened, and free of rocks, debris and large clumps. The grading is a balanced mix of sand, silt and clay.

Screening is the part that matters on stony glacial till. Native soil here comes with the stones the glacier left in it, and a load that has been run over a screen arrives without them. It spreads off a rake evenly, it beds seed properly, and it does not blunt a tiller in the first pass.

Balanced sand, silt and clay means it holds moisture without turning to a brick. It is a growing layer. It is not fill, and it is not a base.

Depths for a lawn, a shoulder and a bed edge

Stony till, ledge, and the mud-season rule

Much of this state is glacial till with granite ledge close underneath, and that decides how deep you can go. Where the bar hits rock at 6 inches, you are building up rather than digging down, and the finished grade needs enough fall to shed water off the shallow spot.

Sandier ground in the river valleys is the easy case. It drains, and it takes a deeper working layer without complaint.

Two rules for the calendar. Do not spread on saturated April ground: you will compact it under your own boots and the soil will set like it was poured. And do not spread onto frozen ground in November hoping for spring, because meltwater runs the fines off the top and takes them into the ditch.

Between the end of mud season and the fall freeze, on ground that is damp rather than wet, is the working answer.

One more thing the till does. Native ground here is often compacted hard a few inches down, and soil spread on top of that sits in a layer with nothing growing through the join. Rake, fork or lightly till the surface you are covering before the loam goes on. Roots that cross the boundary hold a lawn through a dry August; roots that stop at it do not.

Yardage for a lane shoulder, a boat pad verge and a path edge

Three hypothetical jobs. Screened loam runs about 2,200 lb per cubic yard on this site's published figures, near enough to 1.10 tons per yard, so the tonnages below are approximate. Other shapes and depths go through the topsoil calculator.

Shoulder along 250 ft of lane, 3 ft wide, 4 inches

• 250 x 3 = 750 sq ft
• 750 x 4 / 12 = 250 cu ft
• 250 / 27 = 9.26 cu yd
• 9.26 x 1.10 = 10.2 tons

Verge either side of a 35 ft boat pad, 4 ft wide each, 3 inches

• 35 x 4 x 2 sides = 280 sq ft
• 280 x 3 / 12 = 70 cu ft
• 70 / 27 = 2.59 cu yd
• 2.59 x 1.10 = 2.8 tons

Edging both sides of a 60 ft garden path, 18 inches wide, 2 inches

• 60 x 1.5 x 2 sides = 180 sq ft
• 180 x 2 / 12 = 30 cu ft
• 30 / 27 = 1.11 cu yd
• 1.11 x 1.10 = 1.2 tons

Add roughly a tenth to each for settling, and round up. A wheelbarrow left over is easier to deal with than a wheelbarrow short.

Where to put the pile so the lawn survives

Delivery is arranged at checkout by ZIP code, and the truck wants firm ground, room to back and clear height for the body.

Soil is heavier and stickier than stone. A pile left on grass for a week kills what is under it, and a loaded truck crossing a soft lawn in spring leaves ruts you will be fixing for a season. Put the drop on the drive or on a tarp, uphill of the work if the ground slopes.

Then move it promptly. Screened loam that sits in a heap through a wet week packs down and comes apart in clods, which is precisely what the screening was meant to prevent.

Have the quantity worked out before you pick a date. Set both on this page, and if the job also wants garden soil or shredded mulch, put them on the same delivery.