We've had people trigger the radiation detectors coming into the nuclear plant due to eating too many bananas. One person in the USA I believe had radiation poisoning from eating too many Brazil nuts. I think the max you should eat are 1 or 2 per day. It does have to do with where they are grown and natural soil radiation. It's everywhere around us and some places just have higher levels than others. Not necessarily dangerous - that's how it is. Shielding is not necessary from such low radiation levels. You will get much more radiation directly from the sun, flights, medical x-rays, rain, snow, etc. I also assume nobody sleeps in their plants, soil mixes, smoke detectors, antiques, propane lanterns, or counter tops all day long every day of their lives. For shielding against significant radiation levels we primarily use heavy concrete, water, lead, and distance.

Base thicknesses vary, depending on where you live (freeze/thaw cycle), but here in Chicago we would normally have 10" of total excavation for a brick patio with 6 1/2" of CA-6 gravel base, 1" of bedding sand and then the brick. Your attached photo shows the correct limestone for a patio base. But regardless of where you are if you don't do all the excavation now you will have to remove massive amounts of material to get to the proper depth later. Decomposed granite makes a very nice patio and is all the rage right now in the Midwest. If you opt for that scenario, then simply excavate 4-5", lay down a soil separator, spread and compact your limestone and then add the decomposed granite. 3" of limestone and 2" of granite works nicely. Compact the granite and you are "good to go" Here is a decomposed granite pathway, done in 2006 that I photographed a couple of years ago. The only downside is that they are not kind to bare feet. Otherwise they are a great aesthetic.

Sorry it took a while to respond. Our kitchen was destroyed two years ago (which is related to this discussion) by cast iron pipes that had rusted underneath our concrete foundation. So life here is wackadoo. So, the reason I became concerned about the foundation is convoluted. First things first, our house sits on hard clay soil. Because our pipes needed to be placed, our wood flooring had to be pulled up and trail of concrete needed to be jack hammered out from our bathroom to our kitchen. The trail goes through our office, our family room and about four feet into the kitchen. So we can see quite a bit of what the concrete looks like. In doing this, we found out that our concrete (and apparently most houses built in San Diego at the same time) has no rebar. And we have a large crack that basically breaks our slab in two running right down the middle. The slab is about 1400sf and maybe 4x3 ratio. A year ago, we got hit with a major rain storm and that's when I noticed the concrete patch (that had been dry for months, look wet. We called the repair guys back and they agreed it was probably moisture from underneath. They weren't sure if we needed to be concerned. I did notice a large pooling of water about 15 feet from the house just past our back patio which concerned me because I was thinking that maybe that had something to do with that. Or maybe that was a sign that some areas closer to the house might be softer soil and might be allowing too much water under the foundation. So I was thinking about just pouring concrete in the space between our foundation and the sidewalk (about 1 foot out from the foundation) so that we might be able to put some short planters that with drainage that would force any water (rain or from watering the plants) onto the sidewalk. So we got quotes from concrete guys and it was really expensive. Then I read about decomposed concrete and thought that if it was less porous than our dirt (obviously it's more porous than concrete), it might be enough of a solution. But I don't know when then planters would be going in. I could be "tomorrow" or two years from now (my family takes a loooong time to make decisions). So that's where things stand. I really appreciate everyone's input and guidance. You guys could be saving me a ton of money by keeping me from doing something stupid. :)

You don't even need to be under an HOA to have restrictions. Many municipalities prohibit RV, camper van or boat parking on the street or in the front where it is visible. Backyard only or completely under cover (garage, etc.) Check first. Any kind of crushed rock will work.....it doesn't need to be DG. The entire driveway and parking pad at my house is 5/8" minus gravel. Has been there for more than 30 years with only occasional touch ups. It generates very few weeds due to usage but that is the routine coming and going of cars. A parked vehicle may not produce similar results.