I am going to begin construction of the permanent engine house instead of building a temporary building since the elevation of the car barn (lower 3 stalls) is required so that the car barn turnout switch on the switchback is installed in the correct location.
Once the foundation location is laid out, I will begin on the lowest part (car barn) and dig out the foundation. The bottom of the foundation walls need to be at least 1' below the surface to be below the frost line. The wall will be stepped up the slope and the lowest section of the footing connected with rebar so it is more or less monolithic. The result will be the upper section of the building (the engine house) will be above grade about 4" which means all the area in front of the building will need to be filled in - a good use of all that driveway gravel that trucking company brought me instead of clean, washed, 6/7 size gravel...
The length of the building I want to be around 18' to 20' long. The doors are 30" wide and 36" high so I should be able to park any equipment in this building. The upper section will be heated by hot water from the water wood stove (which will be plumbed in from the back of the shed next to the bridge.) Power and water will also be placed in this same corridor. Power will feed over from the barn alongside the hot water lines to the barn's heater. Water comes from the house inside water lines already laid to the water wood stove and will continue to the engine house - that way the water lines are always in a warm zone and will not freeze. I could run the steam engine year 'round this way. The water line will also continue alongside the pipe towards the barn to a water tower to be built alongside the tracks near the north abutment of the Dogwood Bridge.
When completed, the building should hold up to 9 narrow gauge rail cars and up to 4 locomotives. (Some narrow gauge cars are over 30 scale feet in length...)
Numbering the stalls from left to right as #1 through #5, the #1 stall will be mainly for diesels. Stall #2 will be for the #20 steam locomotive since it leads out onto a raised "bridge" section which is handy for getting under the locomotive. Stalls #3 through #5 will hold various rail cars.