Hi, I thought I would pop in and add my 2 cents here. First let me tell you that when I was a kid my dad put in a sunken patio. It was 18" below grade and he put down sand and then layed in brick. We had very heavy clay soil so it was thought that settling wouldn't be much of an issue. After a few years the bricks had settled here and there, with standing water after steady rains pooled in the low spots and took quite a while to drain off resulting in some areas accumulating moss. A little slick to walk on and a bit of a hazard after a long time. The bricks were also no longer tightly layed next to each other either. After less than 10 years he ended up laying a piece of outdoor carpet over the bricks to hide the unsightly moss and reduce the chance of slipping. Even with scrubbing the moss regularly with bleach to remove it he ended up losing the battle. My husband (a bricklayer by trade) put a new patio in at our home and used a limestone screen base. It has been 2 years and there is no settling at this point. Weeds are at a minimum. Occasionally we will have a few pop up but they have been very easy to pull. We used large irregular sized pieces of sandstone for the patio that were reclaimed old sidewalk squares that we decided to break and make into an asymetrical pattern with a brick spiral in the center. So far so good with the crushed limestone base. Excellent drainage, no standing water even after heavy rains. we did install a french drain below the crushed stone to promote even better drainage as well though.

25 years ago I had to choose between stone dust and sand when laying a brick patio using standard sized bricks. The underlying ground here in Virginia is fairly high content clay, I can absolutely state that stone dust is the way to go.... here are a few pointers; 1. Use a rigid but moderately flexible edge guard to define the area. I used aluminum about 4 inches tall. Don's use something softer like plastic or nylon as it will flex and your bricks will start to migrate all over the place no matter whether you use sand or stone dust. 2 . Use 4 inches of stone dust, but apply 2 inches first...then compact it with a manual or mechanical tamper....then thoroughly soak with water and wait a couple of days before applying the 2nd layer of stone dust and tamping and watering again. (BTW, I really don't understand the comments about stone dust not draining well....you will see the water soak quickly through the stone dust.) 3. Make the area as level as possible using a screed (look it up :) 4. Install some water permeable landscaping membrane on a fairly well leveled area. This will promote drainage and stop weeds from infiltrating from below. I will also make it easier to slide the bricks into place. 5. Install the brick. Either full size bricks or the thinner pavers. I used full size bricks which are more stable. To ensure that the bricks are level with one another, place a piece of piece of wood (approx 3" x 8" by 3/4" ) across the surfaces of the brick you are working on and its adjoining bricks...then hammer it with a large mallet until they all the bricks are even. Give then some good wacks...full-sized bricks can take it so long as you use wood as a buffer. Be gentler with the thinner pavers. 6. Depending upon your personal preference, you can butt the bricks directly up against one another or place a think spacer between them. I use pieces of asphalt roofing shingles to maintain uniform spacing. I like the look and using spacers allowed me to adjust the alignment for bricks which may not be uniform size. 7. Regardless of which way you go on item 6, sweep stone dust into the joints between the bricks. Wet the area, let it dry and repeat again. The irregular shapes of the stone dust will lock the bricks into position much better than sand, which is more round. Sand will not get into some of the smaller joints between bricks. 28 years later I am still VERY happy with my results. Occasionally a nearby tree root will distort things a bit but that will happen with either sand or stone dust. I just remove a few bricks and cut out the root. The only periodic maintenance I need to do is sweep new stone dust in the spaces between the bricks one ever 4-5 years. Good luck.

I can't believe your installer did not put edging stone around! Highly unprofessional! I wouldn't think that would survive intact through the first winter. It's trickier to install edging stone AFTER the patio is installed, it should have been done at the time. Two choices that I can see: - buy edging stone like large pieces of cut granite. Many cities use this kind of stone for curbs. It needs to go below ground level. I have a hard time seeing this work effectively unless you use VERY large pieces now. The problem is that years of water coming through the patio and frost heave will be pushing it out. It should have been installed with a deep foundation and probably mortared together. Might be too late. (your installer never thought of this???) - you may prefer to get a few loads of topsoil in and have a gentle slope from the patio to the lawn. It would probably be easier, and would nicely eliminate the step from the patio to the grass. To be effective and not look funny, it will have to be a small gradual slope, so you are probably looking at adding topsoil 8 feet or more from the edge of your patio. That is a lot of topsoil but I think would give you nice results.

Let it settle, or accept that you will be lifting and relaying the rocks to compensate. In Zone 9, where you have no freezing and frost heaving to deal with, there is absolutely NOTHING wrong with laying flagstone on plain dirt. I'm doing a path and patio now, and it's going right on top of the packed dirt, with dirt added or removed to level the stones. The only question is how rustic do you want? If you absolutely want a perfectly level, needs no adjustment ever patio, you need to do the expensive kind with rebar, concrete and all the rest. If you are willing to accept some differences in level, and to occasionally have to reset a stone that has drifted off-level ... laying it on dirt or sand is perfectly OK in your climate.