
Wegmans sells a package of unadorned, pre-baked gingerbread house pieces for about $5, and that's what they used. They trimmed the front pieces and cut the roof pieces in half lengthwise to make a Gambrel roof. They cut holes in the side pieces for windows. I wasn't there for this step, but my guess is that they used a Dremel tool to do the cutting.
They stained the barn pieces red by painting them with food coloring. They made some sort of a thick black concoction for the roof.
They used a glue gun to put the barn pieces together. That wouldn't fly in a gingerbread competition, but this wasn't a competition. It was more dependable and less messy to use than royal icing.
They also had made a pond by putting hard candies on parchment and baking them until they were melted. Then they shaped the pond to their desired shape.

Their sculpting medium: Tootsie Rolls candies. Wait until you see the things they can do with Tootsie Rolls!

The trees were made by covering sugar cones with green frosting. Each had a Tootsie Roll bird on top.
Note the use of white space. Because they didn't feel the need to cover every bit of snow, you can appreciate the details.

Want to see some of this talented family's past creations? Here are some:
The Zoo from 2009 (Some photos are missing. I will try to remedy that.)
The Pretty House from 2007
Another Pretty House, from 2006