Decide on a rate for administering the landscape installation and draw up a contract. Pay particular attention to using whatever approach works for you to get everyone accepting that you will be supervising the installation crew. Since this is not your own crew and may not have any training in or inclination towards careful and correct landscape installation I see extra potential for difficulty. I've had contractors turn on loud machines and walk away with them while I was still describing how I wanted my design to be implemented, because the client unexpectedly phoned me to come and supervise at the last minute--without impressing the contractor with their desire to have my design done as drawn. Such political problems are not rare, based on tales of woe related by others.

Builders are not landscapers. If you decide to go with this plan (it will probably be the last time you do it), write up a set of VERY detailed specifications and have the builder sign off on them. I'd have separate specs for the quality of the plant material, the handling of the plants, site prep., planting, etc.

Go over the specs with your client first and then ask for two meetings....one with the clients and the builder. And then with the builder and his workers (and the clients, if possible).

Make sure that your client understands clearly that the preparation of the site, careful and proper planting practices, and good aftercare are all critical to the health and well being of their landscaping investment. A successful landscape installation is one that looks fabulous in 5 years, 10 years down the road (as opposed to 30 days). Sloppy or improper installation practices is like throwing money down a hole.

Here's something to ponder. Think about the mess that most building crews make and leave on site during and after construction. Do you think that that same crew is going to want to rototill that compacted soil with plenty of amendments, and then carefully rake out the piles of debris? Or are they going to want to pour a bunch of fill on top and grade right over it? ;-)

Actually putting good topsoil on top is generally a better technique than amending. Organic amendments decompose and allow the soil to settle, return to its original condition. You could till in sand but it takes a huge amount to alter the structure of a soil that does not already contain alot of it. And then you may end up with a sandy soil that leaches out and drains excessively.

Adding a layer of top soil without incorporating it into the native soil is asking for problems if the existing soil is clayey (and thus seriously compacted during the construction process). Construction layers cause big problems for plants (including turf). I actually consider top soil an amendment, and in many cases a good top soil is all that is needed. But I would never (having learned) simply apply it in a layer to the surface of the existing site.

The remarkable thing about adding organic matter is that that very simple act can begin a self sustaining cycle within a soil that may have been deficient in OM. Again, I'm speaking of those clay soils with which I have had to do so much work. Adding OM increases the micro 'herd' within a soil, which thus increases particle aggregation and porosity. Microorganism populations themselves add to the organic content. The root systems of plants add quite a bit of organic content over the season (sloughing), too. The addition of organic mulch continues to add OM to the system, and on and on.

A chisel plow blade is a big help in incorporating (and breaking up compacted under-layers) top soil/organic matter with existing soil.

Sand should never be used as an amendment, unless one is prepared to remove the greater percentage of native soil and replace it with pure sand. Sand is fine on the artificial (practically soil-less) soils of a golf course green, but not mixed in with real soil.

See Whitcomb, ESTABLISHMENT AND MAINTENANCE OF LANDSCAPE PLANTS (Lacebark Inc.).

It is true that finding good topsoil can be a problem, artifical mixes sold in its place resembling what you get when you mix organic amendments into mineral subsoil left on the surface in commercial developments. I have taken a 3-way or 5-way mix and put it in a jar, shaken it and watched the components separate into mostly undecomposed organic particles and fine-textured mineral components (silt and clay) over a period of months. Dirt pudding, anyone? The visual resemblance of such "soil products" to certain foods is probably intentional, just like the pet food ads that talk about "gravy" and make other human food comparisons.

Here is a link that might be useful: Myth of Soil Amendments, Part III

That's a pretty good link...can you imagine anyone suggesting one part OM to two parts soil? Oy! I believe it, though. I have seen some incredibly ignorant and downright irresponsible architect's specifications!

The great thing about OM is that a little bit goes a long way. A very long way. I do disagree with her comment about the soil returning back to it's original state. Unless it is barren of all life, it is not likely to do that.

Jenny, contact me off-line, as I have a question to ask you....