Now i have to glue all the different parts together and to had a roof.

Now as it will be partially destoyed, i need the different planks composing the roof to be '"divised'" so that the breaking of the roof could look natural. This is why I traced all the different planks of the roof with the other side of the X-Acto knife: I crush the balsa wood instead of cutting it which helps for the bending of the roof surface.