#4 Crushed Stone: 3/4 to 1-1/2 Inch Rock for Texas Water Problems

Storm season sets the deadline on drainage work in this state. Between the spring storm line through North Texas and tropical rain arriving on the coast, the window to open ground, get stone in it and close it up again is the dry stretch in between, and anything still half-dug when the rain arrives becomes a clay soup. #4 crushed stone is the coarse end of the range, angular pieces roughly 3/4 to 1-1/2 inches across, and it is bought for the jobs where water has to move in volume and the layer has to hold up under a loaded machine while it does. The questions below are the ones that come in about it, roughly in the order they get asked.

Does it have to go in before the next round of Gulf storms?

Where it is doing drainage work, yes, or you are digging twice. Open clay soaks up rainfall and turns the trench walls to grease, and a machine working saturated ground damages more than it fixes. Target the dry stretch, get the pipe bedded and the stone in, and wrap and backfill the same week if you can.

Where it is going in as a construction entrance, the timing argument flips. That is the layer that lets work carry on through a wet spell, so it wants to be down before the ground turns, not after. Either way, the constraint here is the rain gauge and not the thermometer.

Why does a 3/4 to 1-1/2 inch stone drain when a base material will not?

Because of what is missing from it. A graded material such as Flex Base carries every size from an inch down to dust, so under a roller the small stuff fills every gap and the layer locks up solid, shedding water off the top. This stone has no fines, and the pieces are large enough that the voids between them are big too. Water does not trickle through it, it runs.

That is also why it will not compact into a driving surface. Pieces key loosely at their corners and stay that way. It carries load by being heavy and angular rather than by being dense, which suits a layer buried under something else.

Where does #4 crushed stone earn its keep on a Texas property?

Four jobs, and they have the same thing in common.

In each one the stone is doing structural drainage work under or behind something. It is never the finish.

What happens if it ends up under a new lawn?

Nothing good, and the volume makes the point. A lawn area 30 by 40 feet is 1,200 square feet. Put four inches of this under the sod and the sum runs 1,200 x 4 ÷ 12 = 400 cubic feet, then 400 ÷ 27 = 14.8 cubic yards of coarse rock buried where grass has to root. Roots do not enter it, water drops straight through it past the root zone, and the first person to put a spade in finds out the hard way.

New lawn preparation over heavy clay wants soil, so screened topsoil is the order. Keep the coarse stone for the parts of the property with a water problem.

How deep does it go under a spa slab, and what sits on top?

A hot tub or spa pad is a small footprint carrying concentrated weight on ground that changes volume between February and August, so the layers matter more than the tonnage. A seven by seven foot pad is 49 square feet; a four-inch drainage layer under it works out at 49 x 4 ÷ 12 = 16.3 cubic feet, or 0.6 of a cubic yard. This site publishes roughly 2,900 lb per cubic yard for #4 stone, about 1.45 tons per yard, so 0.6 x 1.45 puts that layer at approximately 0.9 of a ton.

That layer is only the bottom of the sandwich. Above it goes a compacted base that can actually be rolled tight, and above that the slab or the frame. Below it, shape the subgrade so water reaching the stone has somewhere to go rather than sitting in the voids against clay. This is a worked example rather than an installed job, so run your own footprint through the stone calculator.

Is it too coarse for an 80-foot garden path?

Comfortably too coarse, yes. An 80 by 4 foot path is 320 square feet, and at three inches that comes to 320 x 3 ÷ 12 = 80 cubic feet, which is 3.0 cubic yards. Those three yards would be a surface of fist-sized angular rock that turns an ankle and cannot be pushed a wheelbarrow across.

Paths want small stone with some grading to it, which on this range means Walkway Gravel over a compacted base. The one place this size belongs near a path is underneath a section that crosses wet ground, as a drainage layer with a finer material above it.

Which pipe sizes and drains suit stone this big?

Larger lines, generally. Stone at 3/4 to 1-1/2 inches beds well around four-inch and six-inch perforated pipe and upward, and it is a common choice under and around culverts and in the deeper part of an infiltration trench. On smaller diameter lines the pieces bridge awkwardly against the pipe wall and a smaller washed stone such as #67 Stone seats far better.

There is one more thing to get right before the load is ordered, and it is the reason drainage layers fail. Fine silt traveling with the water will eventually fill the voids and close the layer down. Wrap the stone in geotextile, keep surface runoff from pouring directly into it, and give the run an outlet. When your figures are ready, send the trench and entrance dimensions through the contact page for a quote by email, or set the quantity, date and ZIP at checkout with Texas Rock Supply.