I might be doing a big house cake for my dad's birthday/parents' house warming and the cake will resemble their new house. I'm wondering if anyone could provide some help as far as how to assemble a cake of that size. Presumably I will have to stack some sheet cakes. Would I need to use cake boards inbetween each layer or every 2 layers? Also what would be the best way to do a slanted roof (carved cake, rice krispie treats, styrofoam)? And if I want to make citing out of fondant, should the entire cake be covered in fondant first and then overlapping fondant strips on top?

exactly how big do you plan to make it? The thickness of the cardboard will depend on the weight. how many are you serving?

The roof can be carved from the sheets easily enough. But it also depends on if you are making alot of gables or just a regular roof.

Do you mean siding? You can apply thinly rolled strips of fondant on to buttercream, or you can use a cake comb for the siding if you want to use buttercream instead of fondant.