Today Shapeways send me an email that my print don't look very well. Just as I feared walls was too thin, and stairs fall off.
I have canceled this order and have to re-design. I'm thinking about increasing wall thickness from 0.3mm to 0.5-1.0mm, also floor thicknes from 1.0mm to 1.5-2.0mm and making walls and roof one part. Also I will remove stairs (it will be easy to make with wire and plastic sheet).