River Rock in Pennsylvania: Rounded Stone for Beds and Water Edges

Along the Lake Erie plain the ground runs in low ridges of glacial till and old lake deposits, the winters come with lake-effect snow, and a bed beside a drive gets buried under plowed snow full of grit and road salt from December to March. Wood mulch does not survive that treatment looking like anything. Every spring it comes out matted, stained and half gone. River rock is what people in the snow belt put down when they want the bed to look the same in April as it did in October.

Reasons to put river rock down instead of mulch

Choose it when the ground has to stay covered for years rather than seasons, when water crosses the bed and would carry lighter cover away, or when the bed sits somewhere a plow, a downspout or a roofline keeps disturbing. It does not rot, it does not need replacing annually, and a hose sorts out most of what a winter leaves on it. The mix runs tans, grays, browns and the occasional red, at one to three inches, smooth and naturally rounded.

Skip it where the cover has to be worked through. Any bed you intend to replant regularly turns into an afternoon of picking stone out of soil. Skip it in a bed of acid-loving shrubs that were doing fine under mulch, because stone feeds nothing back into the ground. And skip it where a wheelbarrow, a mower wheel or a tire has to cross, since rounded stone rolls under anything with weight on it.

Two jobs on the list that belong to a different stone

Both of these get ordered as river rock and should not be.

Retaining wall backfill is a drainage job with structural consequences. The zone behind a wall wants angular clean stone that locks together and lets water out, which is #57 Stone or 2B Stone. Rounded cobble does not interlock, so it offers less resistance to the fill behind it, and using it there is a shortcut that is not worth taking.

A construction entrance is the pad of coarse stone that knocks mud off tires before a vehicle reaches the road. That wants large angular stone, and #4 Crushed Stone is the listing for it. Smooth cobble under a loaded truck migrates out from under the wheels, and it will not scrub a tire clean.

Pond edges, splash runs and dry creek lines in the snow belt

Where River Rock does earn its place around here:

• The visible edge of a pond or a small shoreline, where a band of stone keeps the bank from being cut by wave slap and keeps grass out of the water. Keep it to the gentle edges. Where water has real force behind it, the job is armor stone rather than decoration, and RipRap is what holds.
• Splash areas beneath downspouts, and the run between one and a drain outlet, where falling water would otherwise dig a hole in the lawn every storm.
• Dry creek beds that take runoff during spring thaw and summer storms, shaped so the water has a route instead of wandering across bare soil.
• Foundation beds, tree rings and borders, as a cover that stays put through a plow season.

What sits under the stone, because cobble is not the structure

River rock is a surface material. It covers, it drains and it decorates, and it carries no load worth counting.

Under a decorative bed, strip the sod, grade it, and lay a permeable landscape fabric before the stone goes on. That fabric is doing two jobs: keeping weeds down, and keeping the stone from sinking into soft ground over a few wet seasons. Without it, a bed that started at three inches disappears into the soil and you buy it twice.

Under a dry creek or a splash run, the shape underneath matters more than the fabric. Cut the channel, give it a fall, and let the stone line a route that already works. If the run has a pipe in it, that is a buried drainage layer and it wants clean angular stone around the pipe with the cobble only on top, where it is seen.

Cubic yards for 45 feet of pond edge and a 14 by 22 bed

Hypothetical examples, worked as square feet, times depth in feet, divided by 27.

That third line is the wall job, and it is there to make the point that it should be ordered as clean angular stone, not as this. For a bed that is not a rectangle, split it into rectangles, triangles and part-circles, work each one and add them up. At the weight published on this site's calculator pages for one to three inch river rock, about 2,700 lb per cubic yard or roughly 1.35 tons per yard, the pond edge band comes to 2.2 x 1.35, approximately 3.0 tons, and the foundation bed to 2.9 x 1.35, approximately 3.9 tons. Stone is sold by weight, so take the cubic yards to the river rock calculator for the conversion before you set a quantity.

Edging, depth and the first year of a rock bed

Depth is a compromise. Two inches will not hide the fabric or the soil once the stone shuffles around. Four inches of one to three inch cobble gets loose underfoot. Three inches is where most beds land, with a little more in a dry creek channel where water moves things.

Edging is what keeps the answer honest. Steel, aluminum, stone or a cut trench with the bed set slightly below the lawn all work; a bed that just fades into the grass ends with stone in the mower. Around a drive in the snow belt, set the edge so a plow blade rides over the lawn rather than catching the bed.

Through the first year, expect the stone to settle into the fabric, a few leaves and grit to work down between the pieces, and any bare corner to grow a weed. A rake and a hose in spring is the whole maintenance routine. If a corner of the bed wants heavier cover, Large River Rock is the same idea in a bigger size. When you have your number, choose it with a delivery date on this page. Delivery is arranged at checkout by ZIP code and the truck needs a dump spot it can reach and back out of, so pick a hard-standing drop rather than the lawn, and send anything awkward to Pennsylvania Rock Supply through Contact first.