Building a House Extension: 6 Important Things to Consider Before Starting

By Kyle Hoepner

Visions of a grand house extension have been filling your daydreams for some time, and now you’ve decided to make it happen. How best, then, to translate your mental wish list into the built reality of wood, stone, glass, plaster, and luscious upholstery fabrics? Design professionals listed on the AD PRO Directory have guided clients through this process time and again, and are keen to provide pointers that promise an optimum outcome for your home addition project and minimal hassle along the way.

“Be really clear on your goals, both aesthetic and functional,” says Benjamin McGriff, an architect with offices in both San Francisco and Brooklyn, “and try to prioritize them. This helps your architect evaluate options based on your emotional criteria—and may help them dream up even better options that you might not have considered.”

McGriff Architects extended a historic San Francisco home by adding a contrasting, contemporary volume at the rear.

For the uninitiated, the road from fantasy to buildable plan is likely to have more kinks and branches to navigate than you might expect, and many factors can impact the viability of what you want to do. For example, an addition is rarely just a matter of constructing a space that didn’t exist before. “Sometimes people think about only the need for a brand-new family room without [considering] how that space should flow and complement the house,” says Eddie Maestri of Maestri Studio in Dallas. “The reality is, it’s always much more of a domino effect.” Improvements will likely be necessary in the rooms that adjoin an extension, and systems throughout the house—such as air-conditioning and heating—may require upgrades. “Or we might realize that we want to tie in hardwood floors, and to get that to look right we have to redo the floors on the whole first level.”

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Use the programming stage to ask yourself, “What else?” “That’s a significant part of my initial walkthroughs—stepping back and considering what can be improved upon once you have all of these craftspeople in your home,” says McGriff. “Because it’s intensive work, economies of scale make a big difference. If you’re interested in extending your kitchen by five feet, the next five feet won’t be twice as expensive.”

Building a home addition, everyone agrees, will almost certainly take longer and cost more than you expect.

To get a handle on the rough price tag, May Sung of SUBU Design Architecture in Los Angeles recommends bringing in a contractor early during schematic design. “We create an à la carte menu: how much for redoing the entire primary bath, how much for doing the kitchen with such-and-such cabinetry, and so on,” she notes. “Through that exercise, the client can whittle down from there.” Another strategy is to query friends who have done similar work. (Be careful, though, Sung advises: “Nobody’s friend ever tells them what they actually spent.”)

For a young family in Santa Cruz, Tyreus Design created new rooms here and opened up existing ones to offer more living space.

McGriff suggests looking at the value of your project holistically: “The more you can extend the lifespan of your existing home, the more value you get across the board. It can really underwrite spending the money on an addition if it makes the rest of the house work better.”

Along with construction schedules, which are an obvious—if notoriously tricky—aspect of overall project time frame, Bay Area architect Christie Tyreus highlights decision-making as an important variable. “So many people say, ‘I just love picking things out. We don’t need much help with that,’” she notes, and then they quickly find themselves overwhelmed by the sheer number and magnitude of decisions in the queue. “Clients always start by wanting to move as quickly as possible. But the real question is, how fast can you make decisions and feel comfortable with them?” Her counsel: “Lean on your architect or designer” for their ability to triage and organize.

Meet the Designer: Benjamin McGriff The founder of McGriff Architects in San Francisco, sees every home as a portrait of the lives lived within. Find out more…

Site restrictions and permitting are a second zone of concern when it comes to schedule uncertainty. The review time for a project can vary greatly in different parts of the country. “It could take one and a half years of planning and negotiating before you can even begin construction, or it could take four weeks,” Tyreus says. “So call your local building department. They can tell you the process.”

Many families simply assume that they’ll continue to live in their house during construction. Unless the addition is quite small or work is confined to a little-used part of the dwelling, this is not a good idea.

“I always advise clients to move out,” says Maestri. “You’re dealing with interruptions in services like water and electricity. There are nails everywhere, there are people in your yard, there’s dirt—it’s not a great situation. I also find that a lot of contractors don’t want to take on those jobs, either, because they’re really hard to orchestrate.”

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SUBU Design Architecture added two “glass box” additions, one on the second floor and another on the first floor, to this residence in Manhattan Beach, California.

Relocating to a rental with a month-to-month option to extend rather than a fixed term is ideal, in case your project completion date slips. “I usually recommend at least a 60-day buffer,” Maestri adds. “At the end of a really big construction project, you want to give yourself time to work through a punch list with the contractor. And it’s no fun for anyone involved doing that while the house is occupied and full of furniture.”

Perhaps surprisingly, the style of an addition is not a first priority for many architects. They’d rather start from the client’s needs and vision, the nature of the site, and the surrounding built environment, and brainstorm the best response (and look) from there. Aaron Mollick and Michael Troyer, cofounders of Seattle’s Studio AM Architecture & Interiors, are a case in point. “We encourage exploration, especially in the early steps of a project,” says Mollick. “Sometimes people can go in with one thought, and it evolves.” Troyer continues: “We take our clients’ lead on what their wishes are, and then, if there are things that just don’t mesh, we’ll have a group conversation and come up with ideas on how we can make it work.”

Meet the Designer: May Sung The founder of SUBU Design Architecture, a Los Angeles–based architecture and interior design firm, focuses on creating a bespoke and sustainable home for each unique client. Find out more…

When the moment to grapple with style does arrive, however, New York architect Valerie Schweitzer is a strong advocate for intentionality. “Are you breaking away from the rest of the design, or are you continuing with the same vocabulary, the same visual components?” Both can be done well, but, “It’s an either-or. It can’t be in the gray area.” Schweitzer also points out that additions needn’t always be physically attached to a house, and an extra degree of separation may change the style equation. “Pavilions allow more freedom of expression, but require stepping outdoors. Additions allow for seamless integration, while pavilions invite stark contrasts and delightful surprise.”

“First,” says Tyreus, “you want an architect whose work you like. Then make sure they are a good size fit for you. If they do all bigger projects and yours is smaller, they might consider you the small fish.” Studio AM’s Troyer recommends canvassing local real estate agents and others in the housing field for their recommendations. Conduct personal interviews, too, with your top candidates: “Our general feeling is that you either click or you don’t. There’s a chemistry thing that’s involved,” Troyer says.

Finally, let yourself honestly investigate all that’s possible for your addition. “We encourage our clients to bring their own ideas and potential solutions to the table,” McGriff says, “but ultimately the design process is the heart of a great project. A good client, like a good designer, should work to stay open to new ideas, especially those that challenge their assumptions.”

Looking to hire an architect to help you build a house extension? Visit the AD PRO Directory to find an AD-approved professional for your project