A Modern Spin on a Home Addition

Instead of adding a room onto their home, Celestino Piralla and Cornelia Stumpf added a modular 320 square-foot structure that functions as an office with mid-century modern design.


Photography by Richard Johnson

Photography by Richard Johnson

By: Elizabeth Beeler

When Savannah, Georgia designer Celestino Piralla and Public Relations maven Cornelia Stumpf of CSPC Consult Design were looking to find the ideal space for their new office, they didn't have to look very far. The couple sought a home-based office, but was deterred by the thought of altering the footprint of their mid-century home in order to accommodate the extra space. "Additions tend to compromise the original nature of any building," says Celestino.

Instead, they opted to build a new structure. Conveniently located just a few yards from their back door, the outbuilding makes the most of an otherwise unused space.

In terms of design, decisions were easy. Modernist enthusiasts without reservation, Celestino and Cornelia knew they wanted a practical structure dictated by purist principles.

The couple explored modular structures because they're easy to construct, quickly built, and sustainable over time. In addition, modular units are typically less labor intensive, which ultimately results in a more economical price point.

Celestino and Cornelia collaborated with Phoenix-based ASUL and found a modular plan adaptable to suit their needs and site-specific requirements. "With prefab structures you have little flexibility," says Celestino. "But these modular outfits make a lot of sense."

Main steel framework along with bare exterior walls and roof components were manufacturer provided, leaving Celestino and Cornelia with opportunity to complete the design-build project using locally sourced materials and labor. "About sixty percent of pre-fabricated structures come from the West coast," says Celestino. "But the ASUL process allowed us to purchase the drawings and build locally, reducing our carbon footprint significantly."

With its savvy design, the couple's single-room 16 x 20-foot structure with a cantilevered 16 x 8-foot covered porch lives large, providing ample workspace. Initially, the office was intended to be built at grade level. However, the site's location was later determined to exist within a flood plain.

Mid-Century Modern Prefab Addition

See All Photos

1950s Design

The modular structure' steel-based construction technique is similar to the method implemented by California-based architect Pierre Koenig in the '50s for the case study house #22. Large floor-to-ceiling windows connect the interiors with their environment and allow tight quarter to feel more spacious. The argon, double-paned windows maximize natural light– and energy-efficiency.

Porch Panache

On the 48 square-foot cantilevered deck, a blue bench makes a colorful statement. Recessed LED lighting illuminates the space after dark, while weather-resistant gypsum board clad beneath the cantilevered overhang protects against inclimate weather.

Industrial Railings

A series of simplified metal cables serve as porch railings. Held in place with basic fasteners, the sensible approach suits the structure’s modern ethos. "We chose the cable-style railing to maintain the openness of the deck and promote air circulation," says Celestino.

Metal Siding

The "Think Tank's" corrugated metal Galvalum cladding is locally purchased. Held into place with mechanical fasteners, the siding is durable, inexpensive, and easy-to-clean.

An Inviting Entry

The entry's solid core door with stainless, industrial hinges and a commercial-grade lever makes a sunny statement from the exterior. It's zany orange hue was selected to maintain a common thread with the interior palette.


Blank walls set off of a single work of art, allowing it to become the focal point of the western facing elevation. Its muted palette tames the office's modern look.

Eco-Chic Carpet

The couple selected floor tiles comprised of recycled materials. Available in almost every color, the tiles can be combined to form patterns. Celestino and Cornelia chose these floor tiles for their budget-friendly price point. They laid the tiles underfoot in pattern that mimics their company logo.

Personalized Shelving

Above dual workstations, industrial shelving lined with art and mementos lend the space a personal feel. Black and white photos, a vintage camera and a toy kaleidoscope provide layers of interest. Memorabilia reflects the homeowners' personalities and add interest.

Conference in Style

Opposite the workstations, a retro conference table makes a stylish statement. High-backed wooden chairs with orange seat cushions reiterate the room's color scheme. Whether used on walls, ceilings, floors, or furniture, natural wood brings warmth and softens the look of any space.

Bold Lighting

Above the conference table, a hip pendant fixture suspended from a cloth cord adds a soft glow after hours. Its bold orange hue draws the eye upward, placing emphasis on an often-overlooked space. Strategically placed lighting is a critical element to any well-designed office space.

Smart Workspace

Side-by-side desks allow Celestino and Cornelia to collaborate on projects and make efficient use of the small space. Desk chairs scored from yard sales add vintage flair and keep the room from appearing overly utilitarian.

In order to meet insurance and permit requirements, plans were easy adapted with the flexible building approach. Six-foot steel pilings were added underneath, permitting the simple structure to hover above ground like a tree house. "There's an organic language in modernism," says Celestino. "Modern structures are highly adaptable to any environment."

Once approved by the city, the stoic outbuilding referred to as the "Think Tank" was constructed in just six weeks. Situated with large ceiling-to-floor windows on the eastern façade and smaller counterparts placed high on the western elevation, the steel frame building takes advantage of natural light without intruding on the privacy of neighbors.



A retro conference table makes a stylish statement. High-backed wooden chairs with orange seat cushions reiterate the room's color scheme.

A retro conference table makes a stylish statement. High-backed wooden chairs with orange seat cushions reiterate the room's color scheme.

Galvalum exterior cladding chosen for its durability, low-maintenance, and low price point makes a contemporary statement from every vantage. "For cleaning, the exterior cladding is simply hosed down," says Celestino. Maximum insulation in wall, floor and ceiling cavities along with recessed LED porch lighting and double paned, argon windows ensure utility bills are kept minimal.

Weather-resistant gypsum board clad beneath the main structure and porch awning offers maximum protection from Savannah's moist climate. Finishing off the look, a steel staircase offers easy access, and unwavering strength.

On the interior, Celestino and Cornelia maintained the building's smart design. White walls and ceilings with a connection to the exterior through the abundant windows allow tight quarters to feel more spacious. Underfoot, carpet tiles made from recycled materials create a geometric pattern.

Dual desks, filing cabinets, and a conference table and chairs outfit the space with work place essentials, while a hip pendant light adds a warm glow after dark. Industrial shelving anchors the room from two sides, housing an extensive collection of books and objects d art. Sleek solar shades adorn the windows, allowing natural light to fill the room while filtering direct sunlight.

Visually, the modular outbuilding distinguishes the Stumpf residence from the neighboring residences. But in terms of efficiency, the "Think Tank" sets a new standard. With plans to go completely solar in the next decade, this state-of-the-art outbuilding will surpass all expectations. "We have not found any disadvantages," says Celestino. "This structure lends itself perfectly to its intent."

Keep Reading

Next Up

Guest Room Accommodates Glamour

A career move in teaching inspires Heather Ludi to create an elegant guest room with pops of purple

Follow Us Everywhere

Join the party! Don't miss HGTV in your favorite social media feeds.