I just baked a Wilton stand up house cake using a pudding in the mix Cake mix. (Tha's what I had on hand right now). I did not use Bake even strips.

The back of the house puffed up while baking and looked wrinkled (maybe too much air bubbles?). Anyway, when I flipped it out of the pan, the sides and bottom cracked (mainly towards the back area). The front of the house looks smooth.

I have been trimming away the cracked areas but at this rate, I don't think the house is going to be stable (with so much trimming). Can anyone please tell me what I did wrong?

I'm sorry to hear that your house cake is not cooperating with you!! I recently made the house cake and I used a "pound cake" recipe. I went looking on the web and some of them were too complicated for what I wanted to get myself into. SO - I used the "durable 3D and wedding cake" recipe from this website - it is VERY yummy and super easy to make as you just use a cake mix from a box and then add pudding mix and sour cream.....next time try that recipe and it is a very dense cake and stands up easily!