(Stephanie Brick/Sustainable Design Group)

Boxy houses compartmentalized into closed-in rooms are prevalent through the history of residential architecture, from European castles to Colonial houses.

Only in the last couple of decades have we started picking away at walls the way one picks at a loose thread in a sweater. Before long, the entire sweater is unraveled and the entire home is opened up. The ideas of great rooms and open concept floor plans have been more than just an evolution of home design; they have been a revelation.

With compartmentalization in architecture as out of fashion as mauve toilets in bathrooms, open-concept design began to take shape. Rooms no longer needed to serve a single, exclusive purpose, and so was born the multifunctional room. Dining in kitchens, homeworking in dining rooms, watching television in bedrooms — these days, household rooms can have serious identity crisis issues. But with architectural definition and smart interior design, a happy balance is usually achieved as we combine functions and purposes of spaces in today’s homes.

The eat-in kitchen, with a small four-person table off to the side, started gaining popularity in the 1960s. “The Waltons,” a television show in the 1970s, popularized the concept of a true family-style kitchen/dining room combination: The open kitchen space featured a large, rectangular dining table practically in the middle of the room. Fast forward a few decades and the open-concept kitchen/dining room is one of the highest ranked preferences of home buyers today.

Instead of wall barrier to divide the functions of cooking and eating, we now frequently feature the perfect transition between these two “rooms:” the island.

The kitchen island takes on many forms and functions. It can serve as an expansive prep area (sometimes even with integrated prep sink), or as seating for friends and family (better to have an assigned area than everyone underfoot), or as the ultimate multifunction unit for all of the above as well as homework, buffet serving, etc. The kitchen island embodies all that we love about open-concept homes: It is functional, social and adaptable.

But sometimes homeowners are more than enthusiastic to embrace this ideal — they can become desperate for it. Whether it is for the added prep space or the socialization, what defines an island as an oasis, and what kind of island will just sink the whole ship? At what point are you forcing an island (and its ideals) into your space? Is it really worth it, in that case?

The No. 1 one factor is square-footage. Every clients’ uses, functions, lifestyles, needs and wants are different and personal. So, as a designer, I do not like to label a space as objectively and blankly “too small.” That is, unless we are talking about islands.

Whether your kitchen is large or small, consider scale. A 24-inch by 60-inch island can be dwarfed in a large, open room; by contrast, the same size island can crowd a smaller galley layout. So first, we will review some basic number sets.

Twenty-four inches is the typical depth of a base cabinet, and therefore the typical starting depth of an island (that has no seating). As a designer, I like to work with 36 inches (Americans With Disabilities Act recommended minimum) to 42 inches (not too distant between work surfaces) of clearance on all sides of an island. That distance can sometimes be stretched as great as 48 inches, or squeezed to as little as 30 inches, but local codes on egress should be checked before committing to the latter. When you are deciding how much space to have surrounding your island, considering traffic patterns, work triangles, aging in place and appliance access.

Keeping these numbers in mind, the next step is to analyze the overall width of your floor space, which, in this case, is defined as the distance from obstacle to obstacle (cabinet face to cabinet face — or to wall, or to chairs pulled out at a table, etc.). If you subtract 24 inches for an island, do you have at least 36 inches of clearance left all around it? The more space you have, the more you can consider expanding the depth of the island or add seating (which, when in use, will take up even more depth and is important to count). If you are unsure, try using blue painter’s tape to lay out the proposed island on your floor — or even better, cardboard boxes.

There are other options if an island is your dream but you do not have adequate clearance. In the right space (small and slightly rectangular), a shallower island, only 21 inches or even 18 inches deep can work. To maintain proper proportions, though, the length of the island needs to be relatively smaller, as well (maximum 30 inches long). Another option is the mobile island — often a countertop atop a wheeled cart — that is great if you have a corner or other area out of the way to keep it when it is not in use. There are also pullout cabinet islands, that can match your cabinetry and be parked right under your countertop, though these will always be slightly lower than your standard countertop height.

Lastly, if your space is not conducive to an island, consider a peninsula: It’s just as functional (and tropical!) as an island but tethered to the rest of your cabinetry. A peninsula acts to contain a kitchen work area more but, if it is short, can accommodate extra prep space and even seating in areas that are too narrow for an island.

Islands can be wonderful transitions between spaces with different functions, but it is important to consider the architectural design and constraints of your room to ensure that it will be an effective addition and all clearances will work.

Stephanie Brick is senior architectural designer at Sustainable Design Group in Gaithersburg, Md.