The two pictures below show this. One is taken with the flash on, and the other under normal lighting. I'm not sure which is better as the flash shows the white as very bright.
I put the fire team in front to show the building size. The figures are modern US soldiers in 1:72 scale.
I've still got to plaster the roof, which I think I will require mixing the plaster rather than using a premixed tub. Also on the list of things to do on the building is painting the roof trapdoor, and adding texture to, and painting the base.