I think my biggest mistake was not glueing every single sheet together before grouting it. I got a bit over excited, and was so eager to start grouting, that I also used dowel rods through each column, and probably 60 toothpicks to hold everything in place. I used liquid nails to glue some of the main sheets together, but honestly didn't bother glueing everything. I was WAY too excited to get this thing done!
Moral of the story: TAKE YOUR TIME, AND GLUE GLUE GLUE GLUE GLUE. (did I mention GLUE?!) Grout isn't rock hard, so if the foam underneath isn't completely secure and sturdy, the grout easily cracks. This is why the glue is so important, because the foundation of the DIY rock needs to be solid. Because I had never worked with grout, I assumed that the grout would be the most important thing holding this contraption together. When actually, the grout should just be viewed as a thick cover over everything else.
If my boyfriend agrees to help me, I might redo this project again sometime. I really could use his precision and patience with projects. I tend to get so excited and rush through "important" steps. Haha
Also, if you plan on doing this project, make sure you have it sitting on a COMPLETELY flat surface. Again, I was so excited to start grouting that I didnt take the time to clear off a good flat surface. I hurriedly chose an outdoor table for the sole fact that it was cleared off already, and because it wasnt completely flat, I now have columns that don't sit flat on the tile. If you have sand i suppose this wont be an issue, but with tile it is very noticeable. Now, I constantly have to take the entire loft out of the Viv to clean underneath it. Very annoying. And the lopsided columns and staircase really bug me!
Anyway, the main thing you will need for this project is patience... And glue.