Myth: White (or at least light) paint is essential

Truth: A rich color on the walls and ceiling deceives the eye. You won’t feel boxed in, said interior designer Sindhu Peruri of Los Altos, Calif., because when darker paint is used to dissolve a sense of defined geometry, powder rooms and bedrooms the size of a closet will appear larger. Minimizing architectural details also helps. Hadley Wiggins, a designer in Peconic, NY, said she plays with the perception of a room’s size by painting window sashes and trimming the same color as the walls, “allowing the eye to travel in continuous rather than stopping at a focal point or jarring moment of contrast.

Myth: Art should not overshadow a room

Truth: Use oversized artwork to simulate a view. Even the laws of proportionality can be broken when maximizing small spaces, said Brandon Schubert, interior designer in London. “Treat art like a window,” he advised. And while you’re at it, look for paintings with vanishing points. “A lot of contemporary art looks very flat, but more traditional art has perspective,” he said. He often hangs landscapes to add visual depth to even the smallest of London loos. You can achieve this effect with a single substantial piece or a gallery installation, Ms. Salvesen said. As long as the result “looks and feels generous,” she said, so will the space.

Myth: Choose furniture at right angles so as not to waste space

Truth: Curved furniture adds movement and majesty. A neat floor plan often brings out a tendency to squeeze square elements in a tight Jenga-style to “save” square footage. But Rio de Janeiro-based interior designer Juliana Vasconcellos suggested homeowners choose furniture that swooshes. “Normally the rule is to run from the curved sofa, but it gives a sense of movement and the idea of ​​a bigger room,” she said. A rounded coffee or dining table has the same effect. At least, said Seattle interior designer Heidi Caillier, consider seating with scrolled arms or a slightly curved back, details that will smooth out jerkiness. “You can still have curves on a couch without it being big,” she said.

Myth: Patterns will make a small space look busy and look like a coffin.

Truth: A figured wallpaper creates depth. Like the dark paint, imprints the dark corners, “almost creating a trompe-l’oeil effect,” Schubert said. Go for medium to large sized designs. Tiny prints, while quaint and cozy, can magnify the smallness of a room. For the less daring, even the subtle cross-hatching of the grass cloth will add depth to shallow spaces. Installing a striped rug can have a similar result. “It stretches the ground,” Schubert said. He suggests wall-to-wall carpeting, not rugs, which will leave borders tiny and busy.

Myth: Sleek, modern finishes and plenty of room to breathe help a small space feel less confined

Truth: The cozy effect of upholstery and layered textures makes you feel small and the room feels big. Ms Caillier said she was aiming to create “a jewelry box” and advised against “lots of clean lines”. Instead, she suggests plush window treatments, furniture with handcrafted elements, and layers of nubbly textiles. “Every room on its own should sing,” she said, explaining that when everything from a cushion to a side table is “comfortable and thoughtful,” the room takes on an enveloping warmth that suggests a more large scale. Window curtains can play a dual role in low ceiling digs. Ms. Caillier suggests hanging them as high as possible to lengthen the wall.