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I am installing artificial grass in my backyard. 6 weeks ago, I filled the area with base rocks to form the sub-base (3" depth). Then vacation and work got in the way and I couldn't continue the work. Now I am ready to put the leveling sand on top (1" depth). Given the sub-base was sitting there for 6 weeks and there was a bit of rain during that time, does it still need to be compacted with a plate vibrator? I am wondering whether the sub-base has settled on its own by now.

I don't have a plate vibrator and will need to rent one, plus renting a truck to bring it home is a big hassle. If I can avoid it, it's a big plus.

Thank you in advance for your input

Quoc Vu
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  • It's hard to know. If the area freezes and you have multiple freeze/thaw cycles over the 6 weeks, "maybe somewhat" though I'd generally be uncomfortable assuming it was settled on its own without a full winter or a full year of "just sitting there." If the area never freezes, probably different but I have no experience with that situation. Some rental companies may offer drop-off and pick-up service which might be less hassle and cost than a rental plus renting a truck to move it. – Ecnerwal Apr 30 '22 at 01:40
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    What kind of “base rocks”. Crushed stone? Pea gravel? River rocks? How big are the rocks? You’ll get very different settling behaviors with different kinds of rock bases…. – RibaldEddie Apr 30 '22 at 02:33
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    Specifically a plate vibrator? No. Tamped? yes. Ideally before it rained. Now you get to ruin your back with the crappiest tool ever made after post hole diggers. Tamp it. Wet it with the garden hose. Let it dry enough so that you can tamp it again. Repeat until you just give up. Prob fine for fake grass but only way to be sure for a patio is to use a combustion engine to go thumpity. – Mazura Apr 30 '22 at 05:09
  • Think for grass the base is used more for drainage than support, a cement pad would need it to be packed down. Main concern is for it to be flat. – crip659 Apr 30 '22 at 11:10
  • @RibaldEddie I used 3/4" crushed concrete. Rocks came with a good amount of concrete sand mixed with it. Right now, it looks pretty firm except for the lose rock at the surface. – Quoc Vu May 01 '22 at 07:18
  • @crip659 that's also my understanding it is for drainage. I am putting on top 1" of leveling sand which will smooth out any irregularity. My only concern is the area becomes wavy over time as it settles by itself. – Quoc Vu May 01 '22 at 07:25

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Yes you still need the pack the rock!

I hope you did not get pea gravel as it will never pack to create a solid base.

crushed rock or shale still needs to be packed if you want a nice base.

If you don’t do it right the warranty will be void and you end up with paths and wrinkles in commonly walked areas.

Ed Beal
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  • I bought 3/4 crushed concrete. There will be moderate traffic but I am also concerned it might settle under its own weight over time. – Quoc Vu May 01 '22 at 07:27