What you want is organic matter, any you can find and dig into the soil. Compost, leaves, grass clippings etc. What ever is available in your area.

We moved to OKC in 2015 & I got my first real experience with clay soil. First off, clay isn't the horrible monster everyone acts like it is. Clay is normally super high in nutrients, you just have to get it to a usable form. Right now, I'd give anything for a truck load of clay soil, I prefer it over this sandbox of a yard I have now. Most soil particles are like wadded up pieces of paper. Piled together, they still have little pockets of air between them. Clay is more like a ream of paper. The particles are flat sheets, so they stick together & don't allow air between them. So water seeps in but doesn't evaporate like it does in regular soil, and air can't get to the roots. It took me about 3 years to get it to moderately usable, but I'm cheap, broke & lazy so you might be able to get it done faster with a little more effort. That means organic matter, & as much of it as possible.

Dump all your kitchen scraps into the bed, cover with soil, for composting in place. Contact coffee shops & ask for their spent coffee grounds. The grounds themselves aren't as helpful as some claim, but the grit helps break the clay particles up which is what you're really looking for.

Keep a look out for bagged leaves on the side of the road, take them home & chop them up, then use as mulch. Once spring comes, turn them into the soil to help break up the particles. Same with grass clippings, but be aware some homeowners put herbicides & pesticides on their grass which will then be transferred into your soil.

If you know anyone with horses, cows, chickens, rabbits, etc, ask for manure. Just be careful because hay is typically sprayed with herbicides that will then be in your soil. I've known several who lost entire gardens to it & it can take years to fix.

Organic matter is always good, but it really depends on what you want to do with the soil, if you want a lawn, I think sod is best if you can afford it. If I were wanting a lawn as quick as possible, I would plant rye grass. I live in zone 7 and now have new rye grass up to about 2.5 to 3 inches tall, it was planted about 15 or 20 days ago. This is not a great time to start seeds because they germinate and grow slow in cold weather.

If you are wanting to plant trees or plants, just amend the planting area with organic matter of some kind, I use bagged potting soil to mix into the hole. I sorta go by the rule " plant a $5.00 plant in a $20.00 hole". The best money spent is in the hole, not in the plant.

" I sorta go by the rule " plant a $5.00 plant in a $20.00 hole". The best money spent is in the hole, not in the plant. "

Not when you are dealing with a clay based soil!! In fact, amending individual planting holes in any type of soil has long been disproven to be a beneficial practice when planting virtually anything anywhere but that's fodder for another discussion. When dealing with a clay soil it is even more of an issue as the planting hole in clay acts essentially as a bucket or bathtub, holding in the moisture retentive enriched soil and preventing free drainage. The plant roots just sit in overly saturated, slowly draining soil and are subject to rot.....very few plants can survive or even tolerate root rots.

The Bathtub Effect

The Myth of Amending Planting Holes

I’m assuming the sod was placed on same type soil bug possibly builder spread some topsoil. Others might know better whether did establishes regardless of soil prep, but it would worry me enough to watch it ( and water) over next year.
I don’t think you can just throw grass seed on tough soil but maybe?
It might be worth it to do soil test or at least prove your bare “ clay” to see more what it really is. For example, I have a good deal of poorly draining lot I think has clay- ish soil but a main feature that it is full of rocks— but if I pick -axe out a goodly amount the soil itself doesn’t seem so bad ( not loam though !). It’s the only way I can create a planting hole. I have made many raised beds/ lasagne beds over the years at another home, but I feel getting a few inches of rocks out helps the planting areas establish a little deeper, since rocks won’t decay or transform, and fully raised root systems dry out in our dry hot summers.

Anyhoo, it’s true there might be some kind of seeded grass or “ crop” that can work on your soil before your “ real” grass goes in , or on.
I hear the ideas on spreading organic matter but I expect there’s a bit more to it —labor, volume of materials, containment—for very large lawn- type area compared to some specific shrub or flower beds.

Have you priced a load of topsoil to see whether that's feasible for you?

I am not sure you can blow this up enough to read or not, but this is a *Free" soil test in Arkansas. I am sure it is not as detailed as a test that you pay for, but it gives me all the info I need. You can see it is listed as clay soil, I feel all clay soils are not the same. I have 3 gardens and I like a soil test before I start amending them. This is my second garden and as you can see it is in pretty good shape. This test was taken almost 9 years ago, and I expect the garden is still in good shape because I can grow about anything I want to. I pretty much judge the soil by the way the plants look and respond.

My wildlife garden is much like this test, but I cant find the test sheet on it, it is a little low in areas where this test shows " above optimum", and the PH was lower, adding a little lime seemed to fix the PH, the plants look good but no other soil test was taken.

I think it is always better to work the soil a little before planting. I planted 11 food plots for wildlife this fall, the last one was about an acre of rye grass, which I did not cover. Rye grass is smaller seed than what I planted in the other areas. The other 10 spots I planted either, wheat, grain rye, or fescue.

You can buy clover and bermuda with a coating on it that makes it easier to plant and not cover, you may be able to buy other seeds that way also. Clover and bermuda seeds are so small that they are easy to cover to deep

As far as buying topsoil, it just depends on who you know, I bought 4 loads last summer for $100 a load. I felt that I got such a good deal that told the guy I would take all he had at that price, but I have not had any hauled to me in over a year, it was very good soil, I grew sweet potatoes and melons in it this past summer.

I think that you have the right idea about removing as many rocks as you can before planting. I did my southwest pasture that way before I planted Elbon rye about 8 years ago. I had a lot of dozer work done and needed something to come up fast and hold the soil in place.

I will quit boring you with my hair brained projects, but with a 1/2 acre lot, you can have it looking like a golf course in no time at all.

Plant Delights, a really fine nursery that you can trust, advises and uses a product called Permatill for clay soils. It's also sold by Espoma as Soil Perfector.

lacevail 6a, WV , I like the sound of the Permatill, if I were younger I would be checking that stuff out. Once I get my garden soil like I want it I have trouble with moles, voles and gophers. The ad I read said that the Permatill may help control those critter, but I am too old and beat up now to start adding on new projects. I do use daikon radishes some for breaking up clay soil, but I would not try them on a lawn, but they work well for me for erosion control. When I contour a place I often plant the radishes in the drainage path along with grass seeds. The radish seeds will germinate in just a few days and hold the soil in place while the grass gets established. I use the Daikon radish mostly in the wildlife garden and in the pasture for quick erosion control.

Where do you live? Zone 7 only tells you what not to plant for winter survival. It says nothing about your climate or soils. Please be specific. Saying you live in California is similarly not helpful. If you live in Reno, say Reno.

Roots are the best thing for clay soil. Summer grasses and winter grasses are helpful. I would go on to suggest that you only use organic fertilizer until the soil softens up for you.

Have you tried the jar test to see how much clay you have? There are salt imbalances which mimic clay, and the solution for one is not the solution for the other.

Jar Test: take a straight sided jar (olive jars are perfect), and fill it half full with soil. Use a ruler to measure how much soil you have. Let's say you have 6 inches. Fill the jar with water and a small squirt of shampoo or dish soap. Cap the jar and shake it until all the clods are broken up/dissolved in the water. Set the jar down and get your ruler ready. After 1 minute goes by, take a picture of the jar with the ruler next to it. What happens is some of the soil settles within a minute. That would be the sand and grit. Then wait 1 hour and take another picture. After an hour you should have a distinct layer of silt on top of the sand/grit. On top of that you should have cloudy brown water which is too cloudy to see through. After 1 day, take another picture with the ruler. It takes a day or more for the clay to settle on top of the silt. If you have a layer and the water on top is very clear, then the test is over. If the water on top is still cloudy, then there is more clay suspended in the water.

After watching this forum for 20 years, what most people find is they don't have clay soil. What they need to do next is a soil test which goes into the salts (sodium, calcium, magnesium, and potassium). Excessive magnesium can cause moisture retention in any type of soil causing it to act like clay.