I would like to make a treehouse, but have never made a structure where the top is larger than the bottom of the cake. At least, not one that has survived....
How do I go about this? Do I have to make the house RKT or use another material? I'd really like to make it cake, if possible.
Any advice would be great!
TIA

Hi,
To make a tree house with, like you said, a top bigger that the bottom, you're going to need to make a good solid inside structure.

Think Bird Table! (See link Below)
http://www.google.co.uk/imgres?q=bird+table&um=1&hl=en&sa=N&biw=1280&bih=603&tbm=isch&tbnid=vSFg18RNQv9aRM:&imgrefurl=http://www.gardenfurniture-cheshire.co.uk/garden-products.php%253Fcat%253D2&docid=hEbC6Quc1qqamM&w=591&h=900&ei=us1CTsP4BYmGhQeLgrXeCA&zoom=1&iact=rc&dur=172&page=1&tbnh=204&tbnw=134&start=0&ndsp=14&ved=1t:429,r:8,s:0&tx=42&ty=77

Think of this bird table without the bottom support legs, just the middle support leg, and the top without the roof bit, just the flat top, thats basically the structure you would need, a flat wooden board, with a wooden pole (the tree bit) screwed to it and a flat piece of wood screwed to the top of the pole (the bit the house is going to stand on)
Then once you have this solid structure you should be good to go!
Wrap fondant or gumpaste around the tree part and texture it and build the house out of cake!

Hope this helps in someway! Good Luck

Well, when I made my treehouse I used a 9x13 cake as the base and decorated it like the grass with bushes etc and then had a 1" wooden dowel screwed into the base. The treehouse was all cake. It was wobbly but it held up!! I think there's a picture of it in my gallery.