I used the 750mm ground screws from The Ground Screw Centre to build the base for a garden office, as the garden was on a slope and I wanted to avoid concrete. I was very pleased, not only with the service from GSC but also the quality of the screws. They are well built, and fairly easy to install (you might need the ratchet if doing a large number). It only took about 3 hours to install all 20 ground screws, but it took another hour or so to get them all level across the timber base. Once the frame was mounted all the ground screws were sharing the weight.