What Does Interior Design Do?
Understanding the real work behind creating functional, beautiful spaces—and why it's much more than just picking curtains and furniture.
Understanding the Profession
Many people can't tell the difference between an interior designer and a renovation contractor—they think it's just about choosing curtains and picking furniture. Actually, it's worlds apart.
Simply put, architects ensure buildings don't collapse; interior designers ensure living in them is comfortable and functional. Decorators are more like makeup artists for spaces—swapping out sofa covers, arranging a few potted plants. Interior designers do much deeper work: they redesign traffic flow and adjust functional zones, but unlike architects, they don't touch load-bearing structures.
Here's an example: a family of three—the husband works from home, the wife loves baking, and the child just started school. The original layout has a huge living room but a tiny kitchen where you can barely turn around. A decorator might just swap out the cabinet panels for something prettier. An interior designer would open up the kitchen and dining room into an open-concept layout and carve out a study nook in a corner of the living room. The core difference is this—it's not about making spaces look good, it's about making spaces work well.
Breaking Into the Industry
In some places, the industry's barriers to entry are rather chaotic, but in North America, there are proper licensing requirements. The NCIDQ exam is a hard requirement—26 states and provinces mandate that you can't practice under the title "interior designer" without this certification.
You can't just sign up for the exam either. You need to complete coursework at an accredited institution first, then accumulate enough work hours under a qualified designer before you're eligible to take the test. The exam content covers everything from building codes and fire regulations to ergonomics—losing a chunk of hair during prep is pretty standard.
Getting certified isn't a one-and-done deal either. ASID requires completing 10 hours of continuing education every two years. New materials, new techniques, new regulations keep emerging—you can't rest on your laurels.
How a Project Comes Together
Outsiders think it's just drawing a few sketches and selecting some materials. The actual process is much more complex.
Site Assessment
First, go to the site and take measurements—every wall, every pipe, every outlet position needs to be recorded. Old houses are especially tricky; original drawings often miss critical information like load-bearing columns. Without measuring everything yourself first, everything that follows is wasted effort.
Client Consultation
After measuring, the more important part is talking with the homeowners. The more detailed the questions, the better: How many people live here? Who does the cooking? Left-handed or right-handed? Any pets? Any collections that need displaying? Sounds trivial, but it directly affects the final design. One client mentioned having over fifty pairs of high heels—the designer created a dedicated shoe wall that became the most talked-about feature of the entire home.
Finding Direction
Create mood boards—put reference images, material samples, and color palettes together so clients can feel the overall tone. Many people can't articulate what style they want. Terms like "modern minimalist" and "Scandinavian" are overused, and everyone interprets them differently. The effective approach is to show them lots of images and have them point out what they like and what they hate, gradually uncovering their true preferences. Sometimes they say they love minimalism, but their eyes keep drifting toward images with decorative details—meaning they're not actually that minimalist.
Design Development
Present two or three different layout options for clients to choose from. Many people only discover what they truly want after seeing the drawings—someone who initially insisted on a separate study might waver after seeing an open-plan layout. Design is inherently a process of continuous adjustment.
Detailing
Select materials, specify lighting fixtures, choose furniture. This step is the most mentally taxing—every choice must simultaneously consider aesthetics, functionality, and budget. I've seen designers recommend imported marble that looks absolutely stunning, but the client has kids, and marble is vulnerable to acids and scratches—completely impractical. When budgets are limited, money must be spent where it counts. Quality cabinet hardware is worth investing in—it'll work perfectly for twenty years; decorative art doesn't need to be expensive from the start—tastes change.
Documentation
Floor plans, elevations, sections, detail drawings, material schedules, lighting layouts... A full set of drawings for a medium-sized residence prints out to dozens of pages. The more detailed the drawings, the less likely there'll be disputes later. Issues like "the cabinet color is wrong" or "the outlet position is too low"—if they're clearly marked on the drawings, there's no argument on site.
Site Supervision
Submitting drawings doesn't mean you're done. During construction, you need to visit the site, answer workers' questions, and handle unexpected situations. Old house renovations often reveal hidden pipes when walls are opened up, requiring last-minute bathroom layout changes. There's also dealing with various suppliers—inspecting tile deliveries, verifying custom furniture dimensions, confirming curtain pleat ratios... The tasks are fragmented, but each one affects the final result.
Completion & Follow-up
After hard and soft finishes are in place, create a punch list—have the contractors address issues like paint chips, gaps, scratches. After the homeowners have lived there for a while, follow up to ask if anything feels inconvenient in use. This follow-up is valuable for designers too—designs that seemed good in theory might have problems in practice. One example: a designer created a built-in trash bin thinking it would be clean and tidy, but the client reported that having to bend down and open a cabinet door every time they threw something away was really annoying. These lessons only come from follow-ups.
The core difference is this—it's not about making spaces look good, it's about making spaces work well.
Those Design "Principles"
Textbooks talk about balance, proportion, and rhythm, but memorizing concepts is useless. Plain language makes it clearer.
Balance
Standing in a space, your eye shouldn't keep drifting to one side. The simplest approach is symmetry—floor lamp on the left, floor lamp on the right. But perfect symmetry can feel rigid; modern design often uses "asymmetrical balance": a large potted plant on one side, two small side tables plus a painting on the other—different objects but similar visual weight. One client piled all their art collection on one wall while leaving the other three walls empty—walking in, you felt like that wall was going to tip over. After redistributing everything, the whole space felt completely different.
Proportion
Buying oversized furniture for small rooms is the most common mistake. A 3.2-meter sofa in a 15-square-meter living room means you're pressed against the wall when you sit, and you have to turn sideways to walk past. The opposite is also a problem—filling a loft with 5-meter ceilings with tiny, delicate furniture makes it feel empty like a warehouse; you need large-scale pieces to anchor the space.
Focal Point
When every part of a room competes for attention, nothing ends up being memorable. Good design always has a protagonist—maybe a fireplace, a large artwork above the bed, a dining room chandelier. All other elements play supporting roles; they shouldn't upstage the star.
Color
The "60-30-10" rule: dominant color 60% (walls, large furniture), secondary color 30% (curtains, rugs), accent color 10% (throw pillows, vases). You don't have to follow it rigidly, but the general direction matters—not too many colors, and there needs to be hierarchy. The most extreme case I've seen: Tiffany blue walls, orange sofa, purple-red curtains, bright yellow rug. Each is a "trendy color" on its own, but together it was an absolute train wreck. The first step in the renovation was reducing the number of colors.
The Miscellaneous Knowledge Designers Need
Understanding design alone isn't enough. Building codes, fire safety requirements, accessibility design, HVAC systems, electrical and plumbing layouts—you need to know a bit of everything. Otherwise, you can't communicate effectively with engineers and architects, and your designs can't be built.
Many people think HVAC is the air conditioning technician's business, but designers must consider it too. Vent locations affect how furniture can be arranged; duct routes affect how ceilings are designed. One project originally wanted a trackless lighting design in the dining room, but the HVAC engineer said a major duct had to run through that spot—ultimately, we had to compromise.
Building codes are even more non-negotiable. Which walls can be removed, how wide fire escape routes must be, how waterproofing in bathrooms must be done—these are all mandatory requirements. One colleague just starting out didn't know better and demolished a shear wall. You can imagine the consequences.
Building codes, fire safety requirements, accessibility design, HVAC systems, electrical and plumbing layouts—designers need working knowledge in all these areas. Without it, you can't communicate effectively with engineers and architects, and your designs simply can't be built.
Interior design is where art meets engineering, where aesthetics serve function, and where spaces transform into homes.