You might sow a cover crop now, like winter rye, and let the roots do the work. Plus add lots of compost, etc. and eventually the soil will improve.

Or you might just want to get a backhoe and dig out some beds and fill with decent topsoil, and then do the addition of compost, etc.

Then again, raised beds sounds like a great long-term plan. My aching back and hip keep telling me that they wished I had done raised, really raised, like 3 feet high, beds a long time ago.

I have tried for 18 years to grow stuff in our clay soil. From this day forward, I will have only raised beds. Make them high enough and sturdy enough so you can sit on the edge and weed your garden. Use soaker hoses, and cover them with mulch. Water when needed.

This sounds just like clay. You can't work it unless it is moist. Maybe 2 or 3 days after a good rain or a good soaking with the hose. Raised beds are definitely an option. I would use some type of a sharp claw-type tool or pick axe to chop at it. Then I would add your mushroom soil, compost, manure, shredded leaves, etc. I really don't till nor double dig, but just sort of mix it around on top of the "chopped up as best you can" clay below. I would try to mulch with shredded leaves, they are the best stuff.
Good luck, clay grows alot of good plants and hold moisture. I am getting used to it now. Don't try to dig or work it when it's dry, you will injure yourself.
Laurie

Your builder brought in what is termed "topsoil" and that is what you have now so why would you want more? If anything you want to buy some compost, or maybe leaf mold, to put on what you have, and maybe you won't even need to work it in, possibly the Soil Food Web will do that for you, although that takes some time and will not happen today or tomorrow.

If you are thinking long term and can get the work involved done, consider making a permanent alteration to the soil triangle.
My original soil exhibited the same characteristics you describe, though it is silt only, no clay.
Over time sand has been worked in, along with all the organic matter options like compost, manure and cover crops. There is a marginal amount of clay provided when my manure supplier scrapes up his clay bedded stalls with the front end loader.
Since adding sand to clay alone stirs up lots of controversy, you need to read up on it with an open and critical mind.
Raised beds are a sure way to avoid all the above.

For the type of hardpack you have, get yourself a mattock-a shovel will do you little good. You will have to remove huge amounts of the hard red stuff (like bricks) and add considerable amounts of organic matter (shredded leaves, compost, manure) to add loft-earthworms will do the rest. Your local landfill could have free compost & mulch. By spring, you should have some pretty good soil to plant in.

Of several broken handles in my shed, none have come from a mattock. In our area, it saves the knees the shock of trying to punch through clay and rock. Our soil in no way resembles anything we see in the garden shows on TV.

You can also try a San Angelo bar or other similar tool. It's a long heavy bar that you can jab into the hard ground. We got one at Home Depot.

I would mulch the "soil" with a layer 4" to 5" to 6" of your mushroom soil. This will soften the "soil" enough to allow you to dig in the mushroom soil. Once all the mushroom soil has been dug in, repeat the process with an other layer of mulch. Over time you should be able to ammend the "soil" sufficiently to allow easy cultivation.

You could also include other organic material such as leaves in the mulch layer. The mulch depth will depend on what you can handle.

Good luck.

I grew peas this summer in similar or maybe the same soil and actually got a harvest ...I believe the roots only went in roughly an inch and a half lol its hard to believe it worked , but it really did work infact this soil or dirt is such soft powdery dust it blows away in the slightest breeze but becomes the closest thing to permanent cement or concrete when trampled under foot enough, and it doesn't get much better when wet and super slipppery . I have a patch of first year ever harvest strawberries next to this area and the runners from the strawberries are actually taking root in this cement like dirt lol . It's very hard to believe there once was a garden in that spot .It doesn't matter if I try to turn this dirt over with a shovel or frequently rake it because just pouring water on it recompresses it almost immediately and besides raking just etches it , I really think its the same stuff you are talking about , they use that type of dirt along the railroad tracks ... maybe thats why there is so much wild asparagus along raillines lol some soils are just too rich ...there must be alot of salt or lime in my cementy soil and that is good for some plants . It might be worth experimenting .

I know there are certain plants that shouldn't be planted in composted mushroom soil...roses among them but on no account will putting organic matter sitting on top ever make it down to where it can do any good, its gotta be dug in and invite the rains to come and work on staying there.

Back-hoe; that seems a little overboard, but if a large rototiller cant do the job, then I suppose renting such a large machine might be the only way.
Once started, once it gets hold of the earth in front of it, a rototiller---of major size--not one that will just bounce along on top, can work if the handler doesn't shake him/herself and hit the dog while trying to get it in the ground.
Use a spade to start it off. As the tiller works, add the amendments, peatmoss, leaves, compost, topsoil, loam, and hwatever else you can lay your hands on that is organic.
Hay, straw, newspapers, corn husks.....the list is endless.

Get them in, dig them in, crunch them in and then go over and back and forth until at least 6" depth. But any deeper is appreciated.
Rake, level---look to drainage...and plan on overseeding.

Raised beds: That if you have a mind to do, to me, is not the look I would want for my backyard. I know, they grow good plants, great vegetables....but the look would discourage me to ever think I could grow a lawn. And I have a lawn...a great lawn.
Besides that, if your homesite experiences winds of magnitude, then don't even think raised beds; they dry out very quickly and up goes the expense of watering...constantly.

re:
raised beds; they dry out very quickly and up goes the expense of watering...constantly (windy areas)

...don't I know it ! but my raise bed is one foot deep all the soil is on top of plastic with the bottom shredded to allow worms up and water out the soil is very warm and most useful for deep rooting , and as you said raised beds dry out quickly but that is only the first few inches because the wind blows the moisture right out within minutes , watering is like dumping buckets in although it retains moisture quite well below 4 inches and is muddy nutrients at 12 inches . I have a 12 foot sunflower with 12 flowers growing in hard soil the trick is alot of water and well a very long season ...there are specific things which grow good and quickly here that would be things such as lettuce , radish , beets , strawberries ,sunflowers , garlic chives .... (that I know of so far)

I'm in the process of planting 1000 daylily seedlings in a new bed.

The ground is hard black gumbo - rock-like when dry, gummy when wet. We first had the land scarified with the teeth on a box blad, then disked. We ended up with huge chunks of the stuff, which looked like chopped up old rubber tires. After wetting it down with a mixture of dishwasher detergent and water, we have been able to get the chunks down to smaller pieces. We mixed in a lot of organic stuff, but that didn't affect the "mud rocks." Right now, I am having to use a post hole digger to remove enough of the stuff so I can add potting soil, and insert the seedlings.

I ordered Aerify Plus and it should arrive tomorrow. While I understand it won't dramatically change the soil structure on the first spraying, with spraying every two weeks, in time it is supposed to make it much better. It can be sprayed right on top of the plants, and contains micronutrients for them also. You might want to check into it. I sure hope it works for us, because that's the only spot I have for a large daylily bed.

No matter what the advertising hype might tell you there simply is no liquid anything that can add enough organic matter to any soil to make much, if any, difference. Adding to your soil the organic matter that is readily, and freely, available to you (grass clippings, tree leaves, garden waste, kitchen waste) will do more for your soil then anything you can buy.

kimmsr, it is certainly true that adding organic matter is the best way to improve soil, but that takes time -- even years. The problem with clay and black gumbo is that they are extremely hard soils. You cannot plant anything directly in them and expect good results without amending them. If you try and break the hard ground, you end up with clods. I am grateful to the person who sent me an e-mail suggesting we spray the chunks with dishwashing liquid and water, as it did make it better in a couple of days to till. Now, we have a mixture of small chunks and organic matter. It takes several years of adding organic materials to improve this type of soil, and not everyone can wait 3-4 years before planting, especially when it involves a large piece of ground.

We will be spraying with the Aerify Plus this weekend, and again once a week. Will we see results? I hope so. We've certainly added a lot of organic matter, but even with that we still have 3000 sq ft of clods. I'm having to make holes and fill them with compost or potting soil in order to plant the daylily seedlings.