Drain Rock in Pennsylvania: Washed Stone for Drains and Footings

On the hills around Southwestern Pennsylvania the soils are silty and clay rich, the slopes are steep, and water soaking into a clay layer on a slope is the thing that sets a hillside moving. Where roof and drive runoff is sent matters more here than almost anywhere else in the state. Drain rock is the material that gives that water a route: washed crushed or rounded stone from 3/4 inch to 1-1/2 inch, with the dust and fines taken out so the spaces between the pieces stay open.

Is there still a weather window for a drain trench on a hillside lot?

Late summer and early fall are the weeks that suit this work, and there are usually more of them than people think. Clay ground is at its driest then, a trench wall stands up instead of slumping, and the run is finished before the wet season tests it.

Spring is the harder option. The ground is saturated from snowmelt and rain, a trench in wet clay closes on itself, and long wet spells or rain falling on snow are exactly when hillside ground is most likely to move. If a drain has to go in during spring, keep the open trench short and backfill the same day.

Frozen ground rules it out entirely, and so does a lot of rain in the forecast.

What comes off the truck: washed, 3/4 inch to 1-1/2 inch

The load is a coarse, dust-free stone across a 3/4 inch to 1-1/2 inch range, supplied in rounded or angular varieties. The washing is the specification that matters, because dust left on the stone migrates into the voids and the voids are the entire reason the material exists. That coarser range, compared with a single clean size, means bigger gaps and more water moving through per foot of trench, which is why it is sold for drainage rather than as a base.

Does it matter whether the stone is rounded or angular?

It matters where something is bearing on it.

Angular pieces lock against each other, so where backfill or soil is pressing on the drainage zone behind a wall or beside a footing, angular stone holds its shape while keeping the structure open. Rounded stone shifts more readily under that load.

Where nothing is bearing on it, in a dry well or the middle of a French drain run, either works. Ask for one or the other through Contact if the job depends on it, because both are listed here.

Where does drain rock go on a clay slope, and how deep is the trench?

A drain is a route, not a hole. It starts where the water is and finishes somewhere you have chosen, with a fall the whole way. Against a foundation, the stone sits beside and over the footing drain, not under the footing. Behind a retaining wall, it fills a vertical zone against the back of the wall from the base up, with the outlet through the wall or out the end. Down a slope, a trench cut across the fall intercepts water before it reaches the house.

Two things are not optional. A filter fabric between the soil and the stone, wrapped so silt cannot reach the voids, and an outlet at the bottom end that daylights somewhere useful. In this region that outlet placement matters twice over, because concentrating runoff into a hillside is what saturates the clay you were trying to protect.

Can it stand in for bed fill, a play surface or a boat pad?

Three jobs get ordered as drain rock every season and none of them is this material.

Raised vegetable beds need soil in them, which is Garden Soil. Drain rock has one honest role there: on heavy clay, a shallow drainage course under a bed on a flat spot gives excess water somewhere to go. That is a few inches under, not a bed filled with stone.

A playground surface is the one to be most careful about. Coarse washed stone is not fall material and it is unpleasant to land on. Where a play area needs a loose surface, rounded 3/8" Natural Pea Gravel is the listing sold for that.

A parking pad for an RV or a boat is a compaction job, and clean washed stone will not compact. Build the pad on 2A Modified in lifts and finish it with Driveway Gravel if you want it to look finished. Keep the drain rock for the trench that takes the water off the pad.

How many tons for a 60 foot footing drain and a 4 foot dry well?

Hypothetical examples. Cubic feet, divided by 27 for cubic yards. The site does not publish a weight for this grading specifically, so these use the nearest listed family on this site's calculator pages, the 3/4 inch clean crushed stone at about 2,800 lb per cubic yard, which is roughly 1.40 tons per yard. Treat the tonnage as approximate.

A trench that curves is easiest measured along its center line. If the run steps down in depth, work it in two sections and add them. The stone calculator will convert your own numbers if you want a second opinion on the sum.

What has to be sorted before a load of washed stone arrives?

Have the trench open, the fabric laid and the pipe set, because washed stone moved twice is twice the work and a trench left open for a week in clay will not be the shape you dug.

Pick a drop spot on firm ground close to the run, with clear overhead space and room for the truck to pull away. On a sloped lot that usually means the drive rather than the lawn, and a wheelbarrow route planned in advance, because coarse washed stone does not wheelbarrow far comfortably. Set the quantity and the delivery date here once the tonnage is settled. Delivery is arranged at checkout from your ZIP code. If the lot is steep or the access is narrow, say so through Contact before booking rather than on the morning.