I am looking to put a summerhouse in our back garden. At present a reasonably flat area is covered by wood chippings and it seems pretty compact. I was planning to put a base of pea shingle or stone chippings down and laying railway sleepers on top of this to put the wooden summer house on. Is this a reasonable plan and should I plan as if doing a driveway. I was planning to dig down lay sand then chippings to a depth of 125mm, compact this and put the sleepers down. Any advice gratefully received as I have never done this before.