Sub base depth

[Bodge the builder]

Hi

First of all, great website.

I have just pulled up some 24x24x2" concrete slabs from the garden of my new house. They had been laid since the house was built about 20 years ago. The patio had sunk in places and lifting revealed only a sharp sand base.

I have purchased some global stone York Green sand stone flags and intend to lay them. I am not sure what type of base to place? I have read conflicting ideas, some suggestions even state that I would need no 'hard base' layer?

I have also knocked down a garden retaining wall (and built a much nicer one) and have painstakingly smashed the bricks with a lump hammer. I have used these as a sub base but the depth has amounted to only about 10-20mm. (I have not used a plate compactor but intend to soon. This will obviously reduce the depth)

I intended on laying aprox 50mm sharp sand cement (10.1) dry mix and screeding it to get a nice level surface to then lay a mortar bed onto. I am not convinced by the brick 'hardcore base'. Should I purchase some additional materials at this point or will this depth be adequate for my purpose?

Many thanks for reading.

Nick.

[ilovesettsonmondays]

hi ,a sub base of 100mm of type one would be adequate for your paving .if you want to lay the slabs to the original level they were at , you may have to dig out a bit more to allow for the sub base , your bedding mix and thickness of slab. a bedding mix of 4 parts sand and one part cement would be alot better and more stronger and wont cost you alot more in cement .