I plan on converting a corner of the backyard into a firepit area and want to use crushed granite as the surface. The area is approximately 10'x10'.

I plan on digging out the area and laying weed barrier, but is it necessary for compacted sand beneath the granite? The stuff I've read online seems to be about 50/50 split on sand or not.

I would not use the sand. The weed barrier and compacting the crushed granite should be enough.

Weeds will definitely grow in decomposed granite

I was more concerned with settling and stabilizing the foundation with the sand rather than keeping weeds out. Those can be sprayed and pulled.

Whether you're using DG or a crushed stone, no need for sand. Just level out your base, lay down your fabric and spread and compact the DG/stone.

This is exactly what i wanted to hear because I was hoping to avoid the extra trip to the yard to buy a load of sand.

Thanks

We install a lot of dg. As I tell my customers just make sure it is off of your shoes before you go inside, if you have hardwood floors, because it will scratch them. You can also spray it w/ a product called nanopave that will harden it. We mainly use that between flagstone.

I am installing the same and had read about laying some base rock (about 3 in worth) under the DG. Is this needed or is the DG simply enough?

IMO.....The DG is enough. No need for extra base of any kind. Level surface and compact the DG.

I'm thinking the DG is enough.

Tilling and weeding, compacting, laying weed barrier, then topping off with DG while compacting sounds like enough. I'll be investing in a hand tamper for sure.

That nanopave looks legit and I may actually buy extra for our paver patio. The polymeric sand is starting to wash away a bit in some spots.

No need for a base material unless you have existing drainage issues or you're placing in an area that will receive direct runoff or gutter water. In that case, crushed stone below your fabric barrier will help water escape.

I've got about 12 yards of the stuff on my property and only have one spot that requires some attention after heavy, prolonged rains due to drainage.

No need for sand.

I would highly suggest, however, that you spray a good all vegetation killer that lasts as long as possible in the soil, then double layer your weed fabric.

Eventually weeds will make their way through, and it's a PITA to keep it clear. I had a whole front and part of a back yard in PHX that was DG that I had to weed about 2x a year, and it sucked.

Weeds grow in the DG, not necessarily through it (I deal with some of both). But killing everything ahead of time is a good suggestion. As is buying 41% glyphosate solutions in 55 gallon drums.