Set behind a formidable limestone and cast-iron fence, the Groos house is one of Giles's largest extant houses. The Italianate design is dominated by a monumental cast-iron veranda with capitals in the shape of acanthus leaves. The ornate ironwork contrasts with the plain vernacular masonry of random ashlar blocks, having corners marked by beveled quoins. Resting on a coursed-rubble foundation, the house is crowned by an Italianate belvedere and brick chimney stacks rise from the multiplaned roof. After Carl Groos moved to San Antonio from Eagle Pass, he opened a mercantile business and was one of the founders of the Groos National Bank.
In stark contrast to the Groos House are two modest houses at 306 and 308 King William Street, also designed by Giles, who resided at number 308 for a short time. The machine-cut ornamental millwork enhances a decorated version of what was typically a less ornamented vernacular form.