I have/had a similar problem. My home was built on clay soil that had been brought in deliberately. When I dig down into the soil, the first few inches are topsoil, than about 18 + inches of clay and than sandy soil. I tried different amendments to break up the clay like gypsum etc. I found the best thing was to mix in perlite and compost with the clay. If you want to plant let's say a rose bush in that bed, you are going to have to dig down very deep and amend all that soil. On the other hand, do you really want plants located near your house foundation that require a lot of water? I don't think so. Personally, I would dig and amend a foot deep of soil and plant things with shallow roots that are "drought resistant" plants like irises, sedum, hens and chicks, lavender, portuluca (moss rose). Plants that reseed would be a plus.
