I am demolishing an old shed and having a new one built (9mx6m). The new building is larger than the old one and I therefore need to make the existing concrete base bigger. I also want to raise the level of the new base slightly as well as increasing the overall area so there will be new concrete on top of the old slab as well as at the side of it. Are there any special considerations for doing this? I was going to dig out the new perimeter, add compacted aggregate and then pour to the new level of the base....is that ok? Will it bond ok? Thanks for any advice.