Crushed Gravel for New Hampshire Camp Roads and Drives

A camp road tells you what is under it in the third week of March. Where there is a proper layer, the ruts stay shallow. Where there is not, the wheels find the till.

Crushed gravel is that layer. One inch minus, a graded mix of crushed stone, gravel and binding fines, sold here as Crushed Gravel and written on a plan sheet in this state as NHDOT Item 304.3. The item number is how material gets specified locally. It is not a certificate anyone holds.

It goes under the traveled surface. Not on top of it.

The quarter mile that softens every April

The usual order is a stretch of private or shared road that has been patched for years and never properly based.

Frost reaches about 48 inches in the southern towns and 60 or more up north. Nothing you lay is going below that, so the layer is not there to beat frost. It is there to spread the load and keep water out of the wheel track, so the road lifts evenly in the thaw instead of opening holes.

Second most common order: a turnaround, a shed or equipment pad, or the apron where a drive meets a town road and the plow has been scraping it back every winter.

How crushed gravel behaves on till, ledge and valley outwash

Dense till with a hardpan layer beneath it drains slowly. Water perches on ground that is still frozen, the thawed few inches go to soup, and stone pushed into that simply disappears. Shape a firm subgrade first.

Ledge cuts the other way. You cannot dig the section you planned, so you build up instead. The layer sits above the rock, and the edges have to be graded hard to shed water. Otherwise the ledge becomes the floor of a bathtub and the gravel sits in it.

Sand and gravel outwash in the Merrimack and Souhegan valleys is the forgiving ground. It drains on its own, and a thinner section usually holds.

Probing for ledge before you settle on a depth

Take a bar and push it down in six or eight places along the route, not one. Write the numbers down.

If the bar stops at 5 inches in two spots and 30 inches in the rest, you are not building one road. You are building a thin section over the high rock and a normal section either side, and the join between them is where the surface cracks first. Feather that change over several feet rather than stepping it.

Where rock is high across the full width, accept a shallower layer and put the effort into drainage instead. Water leaving the road matters more than the last inch of stone.

Shaping, moisture and the compactor

Order of work:

1. Strip sod and loam off the route. Stone laid on organic material keeps sinking into it.
2. Shape the subgrade with a crown, roughly a quarter inch of fall per foot across the width.
3. Spread in lifts of three to four inches. One thick lift will not pack through.
4. Damp, not wet. The fines need some moisture to lock around the larger stone.
5. Compact every lift. A plate compactor on a pad, a roller or a loaded truck on a road.
6. Cut the ditches last, so the water you shed has somewhere to go.

The working season runs from the end of mud season into late fall. Frozen ground will not compact. April ground eats loads.

Crusher Run and Driveway Gravel next to it

Three materials that look alike in the pile and do not do the same work.

Rough rule for a New Hampshire drive: crushed gravel low, a surfacing stone on top, and neither of them working alone.

Yardage for a flagstone walk, four raised beds and a play area

Three hypothetical jobs, all using crushed gravel as the layer underneath. Crushed gravel runs about 3,000 lb per cubic yard on this site's published figures, near enough to 1.50 tons per yard, so the tonnages below are approximate. Other shapes and depths go through the road base calculator.

Flagstone walk, 40 ft by 4 ft, 4 inch base

• 40 x 4 = 160 sq ft
• 160 x 4 / 12 = 53.3 cu ft
• 53.3 / 27 = 1.98 cu yd, call it 2
• 1.98 x 1.50 = 3.0 tons

The flagstone then beds on an inch of stone dust, not on the gravel itself.

Pad under four 4 by 8 raised beds, 12 ft by 20 ft, 3 inches

• 12 x 20 = 240 sq ft
• 240 x 3 / 12 = 60 cu ft
• 60 / 27 = 2.22 cu yd
• 2.22 x 1.50 = 3.3 tons

The beds themselves get garden soil. The gravel is only there to keep the walking strips between them out of the mud.

Play area base, 24 ft by 30 ft, 4 inches

• 24 x 30 = 720 sq ft
• 720 x 4 / 12 = 240 cu ft
• 240 / 27 = 8.89 cu yd
• 8.89 x 1.50 = 13.3 tons

Round up rather than down. What is left over goes in a pothole.

Ordering a load and landing it where you want it

Set the quantity and pick a delivery date on this page. Delivery is arranged at checkout from your ZIP code.

Before the day, decide the dump spot and clear it. The truck wants firm ground, room to back and room to raise a body. Low branches over a camp road stop a tandem as surely as a boulder. If the road is still soft, a pile up near the town road and a tractor bucket beats a truck buried halfway down.

Still deciding between this and crusher run? Send the question to New Hampshire Rock Supply from the contact page before you set a quantity.