I’ve done 100′s of decomposed granite patios and walkways in northern California and learned a few things as I went along. When I first began, the industry didn’t have a ‘hardener’ that you could add. That made for a semi-successful installation, because in the winter your walkway was mushy at best. With the advent of hardeners, the DG comes out quite nice, with minimal mush.
Get the DG pre-mixed with the hardener (some landscape outfits will deliver like this) or mix on your own in a wheelbarrow per the proportion instructions. Prepare a bed that’s about 5″ deep. Use an attractive edging. I am totally committed to Ryerson header, which is a thin hard steel that’s bendable. That’s because it disappears. It is expensive though, comes in 16′ lengths with its own stake. The other plastic headers are ugly. An alternative are the many colors and types of Trek, which is a recycled plastic material. Use the 1/2″ wide size. The advantage is that its more bendable than the steel, but it doesn’t disappear, so its part of your project design.
Lay down several inches of road base and use a compacter to compact it very hard and tight. Order enough DG to lay down 2″ on top, compacted. Then here’s the secret: apply the DG (with the hardener mixed in good) at the rate of 1/2″ at a time. Then compact. If you apply too thickly, the stuff won’t harden well. The DG has to be moist when putting it down, but not sloppy. Compact 1/2″ at a time till you have your desired height. Sprinkle with water.
Another method I’ve used quite successfully was told to me by the contractor at Strybing Arboretum in San Francisco. All their paths are done this way, and they get tons of traffic. For this method, DON’T use hardener. Apply a good road base foundation of several inches, maybe 3 or 4″. Then apply only 1/2″-3/4″ of compacted DG. Essentially this is a dusting. You will have to reapply every few years depending on your traffic. I used this method for a patio over 4 years ago and still have not reapplied. I think this is a superior method because you completely eliminate any winter mushiness. Even with a hardener there will be some mushiness.
Some warnings: DO NOT try to apply a hardener after the fact. I once went to a potential job where the gardener had installed a walkway, then put the hardener in after he was done. Oh my God! What a mess. The whole thing had to be removed and redone.
Next warning. Do not install DG directly next to an indoor situation. DG tracks. It’s granite and granite gets on your shoes and gets in the house. You need at least a few steps (not many) before you go inside. My son’s elementary school built a new gym for millions of dollars. The landscape architect speced DG as the hardscape all around the gym. That was a disaster. All those kids tracked that DG into the new hardwood floor and ruined it! They finally installed concrete as a spacer.
Next, the materials. Of course, every area is different. DG in the Bay Area came in gray, gold, or dirt brown. I’ve mixed them for different colors. Don’t be afraid to experiment a bit. A new rock came out on the market from a local quarry that was cheaper (DG is expensive. Last I looked it was around $80/yard!). I was able to get ‘fines’ and used that successfully with the hardener for a coral color.
For patios, (see my complete post on patios)I usually don’t like to have a visible drain, so I put the drain(s) on the outside in the shrub area. The exceptions are like the previous post with the photo of the sunken patio. Of course, I had no choice. But really, always remember your drainage.
One neat new alternative to DG is permeable concrete. Its more expensive than ordinary concrete, but it is nicer, much nicer, on the environment. Its fairly new and my understanding is that a good powerwash in the spring opens the pores and keeps it permeable.
Very shortly I’ll be coming out with a eBook on patios, and most specifically how to install DG patios and walkways. I’ve collected hundreds of real-life questions from do-it-yourselfers and all those questions will be answered in this short pamphlet. So look for the link coming soon on my home page. Thanks everyone for your input.