I don't understand what you want to do. The lawn? or garden bed? 6 inches is the standard for a garden bed.l Most annuals need that much for their roots to grow. But if you are planting perennials, they tend to go deeper. For example rose bushes go deeper.

My yard used to be bare, just ugly grass and with very little drainage. I improved that. First I attended to the drainage problem by having a weeping tile installed. Second I started mapping out where the garden beds would be located. Third for the garden beds, I improved the soil. - for me that involved double digging 1 feet deep so I could mix in good compost into the earth. Others may prefer the newspaper type method of killing grass and starting an instant garden bed.. - I can discuss that later. The next thing I had to do was to improve the lawn. That was a challenge. The grass was poorly looking and the soil terrible sticky clay. I started off with adding topsoil and a good deal of it. I raked it everywhere but not so much that the grass is completely blocked from sunlight. Then I reseeded. Every single year since then, I would aerate the yard, top dress, add new seeds. now a friend describes the grass as a carpet. Its that lush now..

for the easy way to do the garden bed.. -- marked out the spot and smother the grass with wet newspapers. Mound topsoil on top of the newspaper, then start planting. Make sure to punch a hole through the newspaper when planting so the plant can reach the soil beneath. The grass will die and become fertilizer to the new plant. That's the quickest way to start a garden bed. It can be 6 inches deep and it can even be deeper if you wish.

Priority ONE is drainage. Priority TWO is drainage. You want the yard to slope away from the house. Turf grasses commonly root down 3"-6" and "topsoil" isn't a major requirement. Healthy turf can grow in sandy to clay soils. A soil test can guide you in determining what if any deficiencies exist with your current soil and what "vitamins" may be needed for a beautiful healthy lawn. Again, drainage is your number one priority. Make sure the topography is landscaped to carry water away from any building.

Rather than go sentence by sentence disagreeing with ianna, I'll just skip ahead to yardtractor1. Listen to him. If your yard is flat and drains perfectly, then any topsoil or topdressing or sand or ANYTHING you bring in (except compost) will screw up your drainage. If you have low spots in the yard where the water collects when it rains, then either 1) bring in enough sand or top soil to level it or allow it to drain properly for your location, or 2) dredge away the area where the soil is damming up the water.

There is no 6-inch standard for topsoil. I find that statement to be hilarious. In my neighborhood in San Antonio my house is on solid limestone with crushed limestone brought in as fill and "topsoil." I have supplemented that with outside topsoil but mostly with washed beach sand. And by the way the extra topsoil and sand messed up my drainage, so that was a long time ago. I'd definitely do it different today. Then my sister-in-law at the beach has about 3,000 feet of sand under her house. So how does this 6-inch standard work? Is that the average of all averages?

Any soil you have, unless it is poisoned with something horrible, can be corrected and turned into wonder soil. If it is chemically imbalanced (99% chance that it is), get a $25 soil test from Logan Labs in Ohio. If it is biologically weak (again, 99% chance it is), then grow grass and begin now applying organic fertilizer.

The effect you are looking for with the high spot in the middle of the yard is called "crowned." Is there a problem with too much soil? Yes. As yardtractor mentioned, drainage is the main problem. But here is a picture of another problem.

This house is in a neighborhood where someone got them started with annual topdressing of 1/4 inch with topsoil. After 40 years the soil is 10 inches above grade. When it rains the soil washes out into the sidewalk and into the street. These people have installed landscape edging just to contain the flow of mud. I have lots of pictures of Topdressing Gone Wild.

I do like how even the stop sign seems to want to escape that property.

What they said, otherwise. If your drainage is good, don't add top soil. Any soil you have can be chemically and biologically resuscitated with the Logan Labs soil test and proper care.

While raised garden beds aren't, per se, an error, it's wise to avoid doing this if possible. Drainage INTO the beds is actually a good thing and means you can water less (although you may also be locked out of some damp-soil-intolerant plants in the process, that's just the way it is).

Stopping the drainage into the beds means the water is going to drain somewhere else. You don't want that somewhere else to be "into the basement."

The dirt by the house must be higher than the dirt in the yard so that rain falls and drains away from the house. Yoiu do not want a mound in the yard that drains water toward the house.

When it comes to topsoil, different situations require different amounts. A lot depends on what you want to plant. You may want to look for recommendations specifically related to what you're intending to plant. I understand your confusion, though. My husband and I are looking to put in some topsoil and we weren't sure how much to put in at first either. Good luck to you! http://www.fishertopsoil.ca/topsoil.html