#89 Crushed Stone: A Bed That Locks Up, Not a Drainage Layer

The order this material most often gets wrong is a drainage one. Somebody has a damp strip along the foundation after the March melt, a neighbor says buy 89 stone, and a load of it goes into a trench where it packs shut inside two seasons. #89 Crushed Stone is an angular stone running from about 3/8 inch down to fines, and those fines are the whole point of it. They are what lets it firm up under a screed board, and they are also why water will not travel through it.

Sized 3/8 inch down to fines, and the fines are what you are buying

Three things off the spec, and one consequence.

• Size. About 3/8 inch down to fines, so it is a graded material rather than a single stone size.
• Grading. #89, carrying some fines.
• Type. Angular crushed stone, with faces that key against each other rather than roll.

Put those together and you get a material that compacts into a firm, even setting surface and holds that shape under pavers or flagstone. The same fines that give it that behavior close the voids, so treat it as a bedding and jointing product and nothing else. When a reader wants both drainage and firmness, that is two materials in two layers, not one compromise.

Where #89 crushed stone belongs on a Front Range job list

What a Colorado winter does to a bed that was never compacted

Clay along the Front Range takes on water through a wet spring and gives it up through the dry months, and the ground rises and drops with it. Add freeze-thaw cycling that can run several times in a single week at altitude, and a paved surface is only as level as the layer it was set on.

That is an argument for compaction rather than for depth. An inch of bedding that has been screeded and then consolidated moves with the base under it and comes back level. Three inches of loose material does not, because every rise and fall in the clay resettles it a little differently and the surface tells you about it by the second spring. The base beneath, and the drainage that keeps water out of the base, are what the pavers really sit on.

Working with a material that is dusty until it is wet

The fines make this load dusty off the truck and pleasant to work once damp. A light misting before screeding keeps the dust down and helps the layer consolidate; soaking it does the opposite and turns a screeded bed into a rutted one. Sweep joints when everything is bone dry, because damp fines bridge across the top of a joint and leave a void underneath.

Base and bedding work goes best from late spring through fall here. Frozen ground will not compact, and a bedding course placed on it is a surface you will reset.

Half a ton for a flagstone landing, two and a bit for a paver pad

Two hypothetical jobs, worked at about 2,800 lb per cubic yard, which is 1.40 tons per cubic yard, and checked twice.

Flagstone landing, 8 by 10 ft, 1.5 inch bed. 80 square feet. 80 x 1.5 / 12 = 10 cubic feet. 10 / 27 = 0.37 cubic yards. At 1.40, about 0.5 tons.

Paver parking pad, 15 by 24 ft, 1.5 inch bed. 360 square feet. 360 x 1.5 / 12 = 45 cubic feet. 45 / 27 = 1.67 cubic yards, so 2.3 tons.

Both figures are bedding only. The compacted base under the parking pad is a separate order and a much larger one, so price the two layers together rather than discovering the second one after the first load has landed. The stone calculator holds up to five areas at once and adds 5 percent by default for the material that disappears into an uneven subgrade.

Choosing a date once the base is down and compacted

The sensible sequence is base first, bedding second, so the fine material is not sitting in a pile through a week of Front Range wind. Pick a quantity and a delivery date here once the base is in, and note that delivery is arranged at checkout by ZIP code and the truck needs clear access to somewhere it can tip. If you want a second opinion on the layer build before ordering, send the dimensions and the surface you are setting through the quote and contact page.