Novice in need of help

[Jane the Novice]

As my screen name suggests I am pretty new to all this so please excuse the daft questions. I have today managed to prise 15 paving slabs from around a paved area in my back garden.( am currently very tired and stiff). I was wondering if anybody coult tell me how deep I need to dig out for a new border. The reason I ask this is because I have managed to remove approx 8 inches of solid clay and below this level appears to be a bottomless amount of builders rubble( mostly large blocks of cement and breeze blocks. I am intending to remove all the clay from the entire bed and refill with topsoil. Thankyou in advance for your help.

Jane

[Jane the Novice]

[Doris_Pinks]

Jane could you not go upwards and build a raised bed, thereby leaving all that builders rubble where it is?  Just a thought from a "lazy sick of moving other peoples rubbish" gardener! ;)  DP

[Jane the Novice]

Thanks Doris...I had thought about going upwards and yesterday did try to find some kind of edging which would all this...ang suggestions?