I’m an interior designer. Here are 6 mistakes people make when designing a bathroom — and how to avoid them.

People commonly forget to incorporate proper ventilation into their bathroom design.

Bathrooms are naturally humid, and without good ventilation, you can end up with mold and mildew. This is bad for your walls and ceilings and it can be harmful to your health.

I recommend getting a good exhaust fan that’s the right size for your bathroom. Some fans even come with humidity sensors that turn on automatically when needed.

If you can, also include a window into your design that can be opened to let in fresh air.

Without enough storage, your countertops can get cluttered and make a bathroom look messy and disorganized.

To avoid this, think about your storage needs from the beginning. What products and items do you use on a daily basis? Where would you ideally like them to be?

Built-in shelves, vanity cabinets, and recessed shower niches are great, stylish storage options.

If space is tight, look for furniture that does double duty, like a vanity with drawers and shelves or a mirror that’s also a medicine cabinet.

Bathrooms see a lot of moisture. If you choose materials that aren’t water-resistant or durable, you could end up with damage and expensive repairs down the road.

Choose materials made for bathrooms. Porcelain or ceramic tiles are great for floors and walls because they’re water-resistant and durable.

For countertops, quartz or solid surface materials are both stylish and tough. You’ll also want to use mildew-resistant paint with a high-gloss or semi-gloss finish to keep bathroom walls looking good.

Good lighting is super important for making a bathroom feel welcoming and ensuring it’s functional for things like shaving or applying makeup.

I suggest using a layered lighting approach. Combine overhead or recessed lights for general lighting, sconces or backlit mirrors for task lighting, and accent lights for highlighting special features or artwork.

One of my favorite tricks is to add LED light strips below floating vanities or ones with open spaces underneath them. This can easily give your space a layered look and a warm ambience.

A smart layout is key for a functional bathroom.

Create a detailed floor plan that considers the placement of fixtures like the toilet, sink, and shower or tub. Make sure there’s enough room around each fixture for comfortable use.

For small bathrooms, consider space-saving pieces like wall-mounted toilets and sinks, or a corner shower unit. Also, ensure all of your doors can open freely without blocking anything.

I love a good trend as much as the next person, but bathrooms should be designed to last.

You might regret your trendy picks when they’re out of fashion in a moment’s notice, just like your favorite pair of skinny jeans. It won’t be cheap or easy to swap out things like tiles, countertops, or tubs if you change your mind.

If you’re itching to try a trend or super bold design, do so with more affordable elements that are easy to swap out like shower curtains or artwork.