Lacking the type of timber needed for fachwerk construction like the earlier houses built in New Braunfels, Castro employed Mexican laborers from San Antonio to make adobe for the first permanent shelters. The Alsatian colonists, however, preferred masonry construction and Castro's own house was probably the first masonry house built in Castroville. The one-and-a-half-story rough-cut native limestone house is coated with lime plaster on the exterior and interior walls. This long rectangular house has two front doors flanked by shuttered windows; the doors lead to the two principal rooms that are connected internally by a single door between them without a central hall. According to Castro's own specifications, the earliest dwellings were to be 16 × 32 feet with an 8-foot-wide rear addition, which in some cases contained the kitchen. Tucked above the principal rooms was a sleeping loft. This floor plan is important because the slopping shed roofline of the house, which extends over the front porch, marks one of the most characteristic design features of the community.
Most of the original roofing materials, thatch or shingle, have been covered or replaced by metal roofs. Like most of the early Castroville houses, there are two internal chimney stacks built into the end walls. According to a photograph of the interior of a demolished Castroville residence taken by the Historic American Buildings Survey (HABS) in 1936, the chimney stack projected into the interior wall of the house and was fitted with a fireplace that had a simple flat-arched wooden mantel. This differs from Anglo-American housing traditions, where the chimney stacks were always placed on the exterior walls, and from early German-Texas houses, where there would be a central chimney stack for a stove rather than a fireplace. The front porch here appears to be a later addition. Another early Castroville house built around the same time as this one is the Burger House ( CJ4).