Washed Sand Where Virginia Clay Keeps Getting Into the Work

The order that goes wrong most often on Piedmont ground is sand that arrived clean and then stopped being clean. Spoil from the trench gets shoveled back in with it, the pile sits on bare red clay through two days of rain, or the bedding layer is laid against a wet clay wall and the fines migrate into it over the first winter. Sand with clay through it holds water, swells, and loses the one property it was bought for.

Clay in the sand, and the winter that shows it up

Washed sand is coarse-grained and has been washed free of clay, silt and organic debris. That description is doing real work. Clean sand drains, compacts predictably in a confined space, and sits around a pipe without holding water against it. Once fine clay is through it, water no longer moves, the layer swells when it wets and shrinks when it dries, and a freeze in the north or the mountains lifts whatever is sitting on top of it.

The failures look different depending on the job. A trench heaves over a utility line. A slab or pad develops a low spot where the bedding layer consolidated unevenly. A bed that was supposed to drain stays saturated after a storm. In each case the material was fine on delivery day and the site conditions undid it.

Washed sand on Tidewater ground and in a Piedmont trench

Where you are working changes what you have to defend against.

On the flat Coastal Plain through Hampton Roads, the Eastern Shore and the river necks, the native ground is already sandy in places, but the water table sits close to the surface and a trench can fill from the bottom. Sand placed into standing water does not compact and will not stay where it is put; deal with the water first. Low, clayey pockets on the same flat ground behave like the Piedmont.

On slow-draining clay east of the Blue Ridge, the risk is contamination from the sides of the excavation and from the spoil heap. Keep the two apart, work when the ground is not saturated, and backfill promptly rather than leaving an open trench through a wet spell.

In the limestone valleys, rock often sits close to the surface, so the excavation is shallower and the concern shifts to where water leaves. Concentrated discharge into karst ground is worth spreading rather than channeling.

Screeding, wetting, and keeping trench spoil out of the sand

The method is the same wherever the material is used: place it where it is meant to be, keep everything else out of it, and let the confinement do the work.

Around a pipe or a conduit, shovel the sand in so it reaches under the haunches rather than bridging over a void, bring it up evenly on both sides, and compact in shallow lifts. Damp sand compacts; dry sand runs and wet sand pumps. Over a subgrade, screed the layer to a consistent thickness against rails or a straight edge rather than raking it by eye, because an even thin layer performs better than a thick one leveled by guesswork. Under pavers the bedding course is deliberately thin, usually about an inch to an inch and a half, and it is screeded rather than compacted so each unit beds into it.

The instruction that saves the most jobs is the simplest: keep the sand confined to the area it was ordered for, and keep excavated soil from mixing back into it.

Checking the edges after a storm, and replacing what moved

Sand is the easiest material on this site to lose. An exposed edge on a bedding layer washes out in a thunderstorm, a bed layer left open loses depth over a season, and anything on a fall migrates downhill in the rain that comes with tropical systems in the late summer and autumn.

Contain it. An edge restraint on a paved area, a board or a buried timber on a bedded layer, and a covering material over a leveling course all keep the sand where it was placed. Check the low edges after heavy rain, top up what has gone, and re-screed rather than adding a patch on top of the loss.

Sand for two raised beds, a play area base and an RV pad

Length in feet by width in feet, times depth in inches divided by 12, divided by 27 gives cubic yards. This site publishes roughly 2,700 lb per cubic yard for washed and mason sand, about 1.35 tons per yard. Treat it as approximate.

• Example, opening up the base of two raised vegetable beds over heavy clay, each 4 ft by 16 ft with a 3 inch layer: 64 sq ft each, 128 sq ft for the pair, x 0.25 = 32 cubic feet. 32 / 27 = 1.2 cubic yards, roughly 1.6 tons.
• Example, a leveling course under a playground surface 20 ft by 24 ft at 2 inches: 480 sq ft x 0.167 = 80 cubic feet. 80 / 27 = 3.0 cubic yards, roughly 4.0 tons.
• Example, a bedding course under an RV or boat parking pad 11 ft by 38 ft at 1.5 inches: 418 sq ft x 0.125 = 52.3 cubic feet. 52.3 / 27 = 1.9 cubic yards, roughly 2.6 tons.

Those are illustrations rather than jobs that were built. Note the second one: this coarse sand is the leveling layer under a play surface, not the soft sand children dig in, which is what Mason Sand is for. Put your own dimensions through the sand calculator, then choose a quantity and a delivery date here. Delivery is arranged at checkout by ZIP code, and a loaded truck needs a clear route to a tipping spot, preferably on a hard surface where a pile of sand will not sink in.