10 meters apart is right next to each other for a Sequoiadendron. I planted one in my garden 15 years ago. I stood back and tried to imagine a giant tree. I imagined shit. What I thought was enough space will soon be an embarrassment. I will have to start cutting down mature trees around it to give it room. It is now about 2 feet in diameter at the trunk base, about 6 meters wide (and that's with pruning some lower branches) and about 8-10 meters high. Much smaller than the smallest branch of a big one.
Luckily I'll probably be dead before a big storm blows it down and takes out the house.....