Screenings: Picking the Week to Bed a Virginia Patio

The week you choose decides more about a screenings job than the material ever will. Fine crushed material compacts into a dense, level layer when it is damp and rolls into a smooth surface under a plate; lay the same load into saturated Piedmont clay after a four-day rain and it turns to porridge that never sets, or spread it in a mid-August dry spell with no water on hand and it stays loose under the plate. Base and hardscape work runs most of the year here. What holds a job up is a long wet spell, and in the mountains, frozen ground in midwinter.

Choose screenings where the layer has to lie flat, skip them where water has to pass

Screenings are the 1/4 inch minus fraction of crushed rock, stone dust and fine angular particles, and they behave nothing like the washed sizes sold beside them.

Order this when:

• A paver, brick or flagstone unit needs an even, firm place to sit on top of a base that has already been prepared.
• A joint between units needs filling with something that packs and stays.
• A low-traffic walking route needs a dense surface that a garden cart or a wheelchair can cross.
• A shallow dip in a prepared subgrade needs leveling before a shed, a deck footing or a slab goes in.

Skip it when:

• Water has to pass down through the layer. The fines that make it bind are the same fines that close it up. A French drain, a trench around a perforated line or backfill behind a wall wants an open washed stone such as #57 Stone.
• The layer has to carry a load on its own. It is a finishing material over a base, not a replacement for one.
• The area sits low on flat Coastal Plain ground where water stands for days after a storm. A material that holds moisture in a spot with nowhere to drain stays soft.

Bedding flagstone, filling joints and leveling a pole barn pad

Three jobs, three different depths and three different finishes.

Flagstone and pavers. Prepare and compact the base first, then screed a thin, even setting bed across it and set the units into that. The bed is there to let each unit find its level, not to carry the patio. Sweep the same material into the joints afterward, wet it, and top the joints up once they settle.

A pole barn or equipment pad. Here the material is a leveling course over a compacted dense-graded base such as 21A, taking out the shallow undulations before a slab or a floor goes down. It is not the structural layer and should not be asked to be.

A single-car gravel drive. A compacted screenings surface over a proper base gives a tight, walkable finish and sheds water well once it has set, which suits a short drive that gets more foot traffic than tonnage. It needs a crown or a fall, because a flat panel of fine material holds puddles.

Where they sit in the build: over a 21A base, not instead of it

The order is subgrade, base, screenings, unit. Every problem this material gets blamed for comes from a missing step in that sequence.

On red Piedmont clay the base does the carrying, because the clay will not. Over the flat, low ground of Hampton Roads and the Eastern Shore, where water sits close to the surface, keep the fines separated from wet subgrade or they will mix into it and lose their grip. West of the Blue Ridge, where rock often sits close to the surface, the base is usually thinner, and the leveling course does more of the work of taking out the irregularities in it.

Compaction wants moisture. Damp material locks together under a plate compactor in thin lifts; bone-dry material shifts under the plate, and soaking wet material moves like a wave in front of it. Aim for damp, work in shallow lifts, and pass the plate over each lift before adding the next.

Yardage for a flagstone walk, a barn pad and a short drive

Length in feet by width in feet, times depth in inches divided by 12, divided by 27 gives cubic yards. This site publishes roughly 2,900 lb per cubic yard for screenings and stone dust, about 1.45 tons per yard, which is the figure used below. Treat it as approximate.

• Example, a flagstone walkway 4 ft wide and 34 ft long with a 1.5 inch setting bed: 136 sq ft x 0.125 = 17 cubic feet. 17 / 27 = 0.63 cubic yards, roughly 0.9 tons.
• Example, a pole barn or equipment pad 24 ft by 30 ft with a 2 inch leveling course: 720 sq ft x 0.167 = 120 cubic feet. 120 / 27 = 4.4 cubic yards, roughly 6.4 tons.
• Example, a single-car gravel driveway 10 ft by 60 ft with a 2 inch compacted surface: 600 sq ft x 0.167 = 100 cubic feet. 100 / 27 = 3.7 cubic yards, roughly 5.4 tons.

Those are illustrations, not projects that were built. Fine material tightens under compaction, so the loose depth you spread sits higher than the finished depth you end up with, and the joints will take a second sweep after the first rain. Check your own figures in the stone calculator, then choose a quantity and a delivery date here. Delivery is arranged at checkout by ZIP code, and the truck needs clear access to somewhere it can tip.