Lets start with a Tutorial for houses and barns in 15 mm style.
My first impression and hinderance was scaling the whole house. So I took two medium bases by FoW and added 2,5 mm on each side. That makes a house worth 8 by 6,5 cm (wide and length). For getting it high enougth I took some sample miniatures and scaled approx 2,5 to 3 cm for the first floor. The roof is again another topic. At this tutorial it is approx 2 cm heigh.
After doing the initial drawings on a piece of paper I transfered it to an old and unused papercard and cut it out with a knife. After that I basecoated it with a special paper basecoat so that it does not crumple somehow and then basecoated it with the real paint. A bit of drybrushing and glueing made a perfect barn for anythere during WW2...
For the colours used here:
Basecoat: Styropor Grundierung "Ideen mit Herz"
Basecoat colour: GW Citadel Undercoat Black
Drybrush : Lukas Cryl Cold Grey
Drybrush 2: Waco - Lichtgrau (light grey)
Windows and door frame: Vallejo Brown
Windows and door frame drybrush: GW Citadel Calthan Brown
Window "glas" : Vallejo Pale Greyblue
Total sizing with roof:
Length : 8cm
Wide: 6,5 cm
Height: 5 cm
Total sizing without roof:
Length as above
Wide as above
Height: 3 cm