A small sanding house and tower, based on photos on this page: www.raggstoriches.biz/DSTsidepage.html as well as research into how sanding houses were used.
The roof over the sand bin was added after I found another prototype photo with a similar layout. Keeping the sand out of the snow and rain makes sense, so I added it.
The sanding facility works in the following way: Sand is offloaded from a hopper into the exterior storage bin. The wet, unprocessed sand is then shoveled into the building via a door in the side wall. The sand is filtered through screens, and dried inside. Compressed air, sometimes from the locomotive, then pushes the sand up the small pipe into the hopper. Sand is then loaded from the hopper into locomotives, which then use it to gain traction on slippery tracks.
Fun mock-up that I hope to put into brick once I stock up on brown and gray parts again.