How much washed rock for under my deck?

Question

I'm about to build a deck in my backyard and was told that I needed to put down weedblock and washed rock under the deck.

I'm not sure how much rock I should be purchasing to go under the deck. The total area that I'll need to cover is approx. 320 ft.

Anyone know how much rock that works out to be?

Answer 1

Put your poly down and 4" of rock on top of it.

320f² x (4/12)=105.6 cubic feet / 27 = 3.91CY

If you are going to compact it add 25% more rock.

You could probably get away with 2" thick of rock. In that case 1/2 the quantity above.