Bedroom and Storage The house’s interior walls are medium-density fiberboard, the sort of material that more typically is covered with drywall. Instead, the fiberboard was coated with a linseed oil to accent its natural, rich tan and finished with a catalyzed var-nish to make it water-resistant. The effect is an interior wall surface that complements the earth tones that dominate the house’s decor and never needs to be painted.  Photo 8 of 8 in Four Walls and a Screw-Top