I am not sure exactly what you are referring to. the stuff I am familiar with is foam with paper on the outside, not good for outdoors. One of the guys on this has done some beautiful buildings using a solid foam which was quite expensive. I wrote an article for the Garden Railways Oct. 2018 magazine detailing building structures using 1/2 inch foam insulation board which is about $10 for a 4 X 8 foot sheet. There are a number of projects on this forum I have posted under the handle placitassteam.
Winn Erdman Steamaholic 291