This is how I go about patio prep 1)excavate down paver thickness plus +- 7" (for 6" gravel base) 2)apply geo textile fabric 3)add 6" of 0-3/4" 'cheap crushed' gravel base (4" is acceptable for a patio, 6" is better especially in Denver climate) seek recycled crushed gravel if available. 4)tamp gravel base with a vibrating plate over two layers (at 3" and 6") 5)top up low spots to make level grade (sloped slightly for drainage in appropriate direction) tamp. 6)apply 1" layer of sand or limestone screening. sand is preferable for flagstone as it shapes to irregular underside of flagstones and drains slightly better. 7)level off perfect grade playing with a 4' carpenters level or leveled pipes and 2 by 4. slope 1" over 4 ft in appropriate direction for drainage 8)apply pavers (tightly) or flagstone 9)sweep in polymer sand to fill in joints 10)tamp, reapply polymer to top up joints, moisten Alternative bases for flagstone- 1)geo textile fabric 2)4" crushed gravel (0-3/4") base 3)4"- 6" Concrete pad with rebar 4)apply thin set mortar with 1/8" notched trowel 5)place flagstone 6)apply mortar to joints, have sponge handy Least thorough option for thick flagstones (2" +) 1)excavate slightly more than 3" 2)apply 1" sand for levelling 3)drop flagstones in place, hammer down with deadblow mallet 4)fill joints with polymer sand, moisten Hope that helps.

pakbrain - I've done quite a bit of this around my house using limestone that I brought up from the creek bed at the back of my property. It was a mix of sizes and thicknesses. The best solution I found is to compact a good 3 or 4 inch base of crushed gravel (#411 around here)then spread about an inch or two of the "screenings" or "fines" that the gravel quarry sifts out of crushed gravel when they are making drainage gravel. It is more stable than sand and is easy to work around and under the stones to level the tops. Stay away from just laying them on dirt. You'll end up reworking them all the time and the grass and weeds in bertween the stones will drive you nuts. Phil

You need to use "crushed gravel" for the base, tamped down, thoroughly wet it down a once or twice over 2 to 3 days - it needs to set up a firm base. Then add paver sand, screed it level or with a slight slope for drainage and wet it down thoroughly - a good rain is great - and let it settle. Of course, some of the sand will fall down into gravel and that's fine. Its important to let this set and settle for 2-3 days. Fine tune the surface and lay your paving stones. I used a level as I went along laying pavers. In your case it may be the size of the gravel that caused so much settling of the sand. I would just get more paver sand and redo the screeding, let it settle with the help of water and go from there. Good luck. Linda

As far as I know gravel is a fairly generic term, and comes in lots of different sizes. Anywhere from say river rock, to large grit sand (as in the 16 grit silica sand I got). Bottom line if using river rock sized gravel (or anything similar) the smaller sand particles will easily take up the space between the larger gravel/rock particles. And when you refer to gravel it's hard for me to picture what your referring to in that regard. The only benefit I can see in using gravel is the larger particle size allowing more air between the particles. That aids in oxygenation of the roots, and drainage. However if the smaller sand takes up that space I'm not sure I see a benefit in mixing the two. So I guess it comes down to just how much difference there is between the two different sizes. Perlite is another good medium to mix with sand/gravel mixtures. Perlite is more porous than vermiculite, and will help aerate the mixture better than vermiculite. Perlite will also help retain moisture in the sand/gravel mix. So I cant see any problems using it. I may even decide to use some also. Although Perlite is very light, and I don't think I will use a lot of it in the mix for my root plants. Simply because I want to maintain weight to the mix (as in traditional soil), and don't want it to become to light. That's the main reason root veggies become deformed from what I understand (but they are still definitely editable, just the shape may be off). That wouldn't be a concern for non-root veggies. I had planed to only add vermiculite because at the time I had plenty on hand that I bought last spring, however most of that is used now and I don't have enough anymore. "My guess is that the beneficial microbes/fungi don't actually clean up the decaying roots, but rather attach themselves to live roots, Protecting the plants from the harmful bacteria/fungi propagated by the decaying roots. Do I have that correct?" For the most part that's exactly correct. The beneficial microbes aren't actually there to devourer the dead/dying roots. Although there is one product that claims to do just that with enzymes (CANNAZYM ), but I haven't had time to look for creditable sources of infromation on it, and find out if it actually does what it claims to. But dead/dying roots are a feeding source for pathogens. The beneficial microbes will help keep their numbers down and from breading out of controls by feeding on the pathogens. But both pathogens and beneficial microbes will not only live on the roots, but within the growing medium itself, as well as in the water. By adding the beneficial microbes/fungi/acids to the solution, the entire growing medium's surface area becomes essentially a bio-filter that will continue to breed the beneficial's, as long as they have a food source (the pathogens) and good living conditions (namely the right water temp). Water temp is also a factor that affects how fast pathogens breed and multiply. I am not well versed in specific pathogen and soil born diseases, but I have seen a list of the different strains and what they protect against. Though I'm not sure if I have it saved to my computer somewhere, bookmarked it, or even if it covers your question. But it will take me a little while to see if I can find it again. I have a lot of articles saved and would be happy to post them if it may help, but you seem to know what your looking for. I wouldn't be able to tell what pathogen caused what. It is my understanding that a high quality beneficial microbe/fungi product will have a wide variety of strains in it. So for the most part I just plan to make sure I use high quality products for that. High Quality Trichoderma products Liquid or granular formulation Mixture of Trichoderma species High CFU or spore count Long shelf life"-18 months minimum Reputable manufacturer Active over wide temperature range Organic certification Low Quality Trichoderma products Refrigerated product Single species product Low CFU or spore count Short shelf life Questionable source Active over narrow temperature range Not organically certified