#89 Crushed Stone: the Small Stone That Packs Instead of Drains

Ask around a Missouri yard for small stone and you can end up with either of two loads that look the same tipped on a tarp, and only one of them will hold a flagstone still through a winter on claypan. That is the whole difficulty with #89 crushed stone. It runs about three eighths of an inch, same as the clean grade beside it on the order form, and it behaves in a completely different way, because this one carries its fines and that one has had them washed out.

What "3/8 inch down to fines" is actually telling you

Three lines make up the verified spec, and the third is the one that decides jobs.

Down to fines means the load is not one size. It is a full spread running from the top size through grit and on into dust. Worked into place and compacted, the small material wedges into the gaps between the larger pieces and the angular faces lock against each other. What you get is a firm, close-knit layer rather than a loose one.

That also tells you where it must not go. Those same fines close the voids that a drainage layer depends on. If water has to travel through the material, the job wants a washed grade such as #8 Crushed Stone or Drain Rock, and the drainage route planned separately.

Joints, setting beds and chip seal, job by job

The joint work is where most Missouri orders go. A flagstone terrace laid on cherty Ozark ground loses its joints first: grit washes out in a June downpour, the stones start to rock, and by the second summer the edges are catching a mower wheel. Topping and recompacting the joints is a morning's work with this material and a stiff brush.

A raised bed, a swing set and a boat pad: one maybe and two noes

The three jobs people most often try to buy small stone for are worth going through plainly.

A raised vegetable bed does not want stone in it at all. What goes inside the frame is Garden Soil, and the only place this material belongs near a bed is the path between them, where a compacted setting course keeps a wheelbarrow wheel out of the mud.

A playground or swing set fall zone is the opposite of what an angular, dust-carrying stone gives you. It is sharp, it packs hard, and hard is the one thing a fall zone must not be. Shredded Mulch is the usual answer there.

A pad for an RV or a boat trailer is a load question. A tandem axle on a wet claypan lot needs depth and a graded base under it, which means Crusher Run or Base Rock built up in compacted lifts. This grade is far too fine to carry that on its own, though it does make a tidy finish over a pad that is already built.

#89 crushed stone in a claypan yard through a freeze-thaw winter

The northeast prairies have a tight claypan under them, and water perches on it from late fall into spring. A compacted layer of fines-bearing stone sitting in that water is holding moisture, and moisture that freezes and thaws over and over is what lifts flagstone and opens joints. January nights run below freezing while plenty of days thaw, so this happens dozens of times a winter, harder in the north of the state than down in the southern Ozarks.

The fix is not a different joint material. It is getting the water out from under the build before this layer goes anywhere near it. On heavy ground that means a free-draining course beneath the setting bed and a route for the water to leave, not a thicker bed. On cherty Ozark ground with rock close to the surface the subgrade is usually firm already and the setting course can be thin.

Expect some joint drop over a first winter either way. A top-up in spring is normal and is not a sign anything has failed.

Yards for 180 square feet of flagstone and a 48 foot path

Two hypothetical jobs, worked through.

A flagstone terrace of 180 square feet on a 1 inch setting bed: 180 x 0.0833 gives 15 cubic feet. Allow for the joints as well, which on a flagstone layout might be eight percent of the area at an inch and a half: 14.4 square feet x 0.125 is another 1.8 cubic feet. That is 16.8 cubic feet in total, or 0.62 cubic yards. This site publishes about 2,800 lb per cubic yard for the #89, #8 and 3/8 inch chip family, roughly 1.40 tons to the yard and approximate, so the order comes out near 0.9 ton.

A garden path 48 feet long and 3 feet wide with a 2 inch bedding course: 144 x 0.1667 is 24 cubic feet, 0.89 cubic yards, about 1.2 tons.

Both of those are compacted depths, so add a little for the drop under the plate. The stone calculator will repeat the sums with depth guides and a five percent allowance that is on by default.

Where a ton and a half should land if the patio is round the back

Small orders are the ones that get moved twice, and moving this material twice is a waste of a Saturday.

Pick the drop spot before you pick the date. A ton and a half of fine stone makes a heap you can shovel from all sides if it lands on a hard surface, and a heap with a muddy skirt if it lands on grass after rain. Plywood or a tarp underneath solves that. Keep it clear of the spoil from any digging, because trench dirt in a joint mix ruins the color and the compaction both.

Delivery is arranged at checkout from your ZIP code and the truck needs clear access to a spot it can tip. When the yardage looks right, choose an amount and a date on this page, or ask through the contact page if the gate is tighter than the approach suggests.