What Is "3 Inch Minus"?

Unless you happen to work at a quarry or have a degree in engineering geology, most of us probably aren’t familiar with common construction terms. If you’re a homeowner, you may have heard your contractor mention “3 inch minus.” 

But what the heck is it, and what is it used for? In this article, we’re going to clear up the mystery once and for all. 

By the end of this blog post, you may not feel like a quarry expert, but you will be able to nod confidently in response the next time your contractor mentions it.

Clean Vs Minus Rock 

For starters, it helps to know the difference between clean and minus rock. When people refer to rocks as being “clean,” this means any rocks that are free from “fines,” which are basically small particles of rock and dust. 

Because these types of rock products don’t have any dust or small pieces of crushed rock, this gives them a cleaner look, hence the phrase clean rock. 

Minus rock, on the other hand, is rock that does contain fines. Minus rock is usually a mixture of different size rocks, with some larger ones and lots of crushed rock with fine dust.

3 inch minus rock means that the largest rock size will be 3 inches. But it will also contain dirt and crushed rock under 3 inches, which are the fines. And because minus rock is basically crushed rock that’s been put through a sieve during production, it also refers to any rock that will fit through a 3” by 3” screen grid. 

Both clean and minus rock come in a range of sizes and are used for different construction applications. For example, there are also 2 inch minus rocks, ⅝ inch minus, and ¼ inch minus rocks.

What Is It Used For? 

Minus rocks are generally used for projects that require compaction. One of the most popular uses for minus rock is as a base for roads and pavement. It’s also a common base layer for gravel driveways, with a finer layer of gravel put on top. Patios, retaining walls, and building foundations also benefit from crushed minus rock at the base. 

If you live in an area with loose soil that contains lots of clay, using 3 inch minus rock as your driveway base is an excellent choice. It will provide a stable, solid surface for heavy cars to drive over. You’ll find that after driving on it for a while, it will slowly pack down into a nice compacted layer. 

3 inch minus is also perfect for driveways that are sloped and prone to erosion. This is because the tight compaction of this size helps prevent it from washing away. 

Shop Sand and Gravel

Starting a new project?

Need Fill Dirt Or Crushed Stone Delivered? We’ve Got You Covered 

At Circle M, we’ve got sand, gravel, fill dirt, and crushed stone for all your construction needs. Choose from a wide variety of sizes and textures including 3 inch minus structural fill, 3 inch minus road base, ⅝ inch basalt minus and more. 

Save yourself the trip and get it delivered with the best trucking crew in the Northwest. We deliver landscaping supplies throughout Spokane. Give us a call today at (509) 928-3255 to speak with our knowledgeable staff.