I've had to make a 4 layer cake and will need to carve it into a house shape.
It was rather wobbly and crumbly so i thought I'd freeze it so I could carve it more easily.

Is this a good idea?

TIA!

You could freeze to help the butter cream set up(if you filled the layers). I wouldn't let it get too hard though, your knife won't go through. Good Luck.