The idea of finishing a basement can inspire the greatest of possibilities: Extra space for that pool table you’ve always wanted! Rooms (galore) for the kids to play! A place to host the ultimate Super Bowl bash that won’t leave your living room in shambles!

And then, of course, there’s the added resale value. It’s a costly project, indeed; in 2017, the average cost to remodel a basement was over $70,000—but homeowners also reported a 70% return on investment, according to Remodeling Magazine’s annual Cost vs. Value report.

That’s perhaps why finished basements have become one of the most popular remodeling jobs over the past 20 years, according to the National Association of Home Builders, with nearly a quarter of contractors surveyed reporting requests for such a renovation in 2017.

But if you’re going to sink that kind of money into a home renovation, you sure as heck want to do it right. These are the most common finished basement blunders—and they’re all easily avoidable.

1. Ignoring that musty odor

Jonathan Faccone has seen a lot of houses. As a professional home buyer in New Jersey, he’s encountered the best of finished basements—and the worst.

“The worst finished basement I’ve ever seen was covered with black mold from top to bottom,” recalls Faccone.

If only the owners had taken a deep breath—literally—before breaking ground on their basement remodel.

“If the space smells and feels wet, spending the money to finish it may be wasted,” he says.

At best, that damp smell will linger and be a turnoff in a space you just spent thousands to renovate. At worst, a musty odor could indicate bigger problems—like mold or even foundation issues.

2. Skimping on lighting

In my time house hunting, the worst basement I ever saw was in a midcentury ranch home. The wood-paneled walls weren’t inspiring, but the lighting was even worse. The homeowners had elected for track lighting; and instead of even, all-over light, this created three bright spotlights pointing to different corners of the room—and dark shadows everywhere else.

It was perfect, for a serial killer.

The basement is “an already scary area,” says Landon Eskew, a contractor in North Dakota. “Utilize can [recessed] lighting everywhere, and control it by putting your room on a dimmer switch. That way, you can set the lighting perfectly.”

3. Forgetting that the basement is still part of your home

On a related note: “The biggest mistake people make in a basement is not treating it like the rest of the home, and not giving it the same amount of attention as the upstairs,” says Leslie Bowman, the founder and design director of Chicago interior design studio The Design Bar. “Elevate the space to avoid that traditionally ‘scary’ ambiance.”

To make the basement welcoming, Bowman recommends creating separate spaces—like a crafting nook, a TV corner, and a cozy office to make the floor plan feel “more purposeful,” she says.

And you don’t have to put up walls to divide the basement: open bookshelves or folding room dividers allow light to flood the space.

And because basements inherently are “very yin energy—damp, dark, and cold,” says feng shui expert Maureen Calamia, you want to counteract those vibes.

“‘Yang’ up” your basement with vivid, cheerful décor, she adds. Choose brightly colored throw pillows, light furniture, and natural fibers and fabrics. And do anything you can to improve the windows.

“Most basement windows are small and high up,” Calamia says. “Light and views of nature are key to a feeling of well-being. Installing egress windows into each room will bring in much more light.”

Granted, this project can be expensive—a single egress window runs around $2,000—so consider perking up one room first.

4. Not waterproofing

Your basement is at higher risk of flooding, so make sure you’ve protected the bones. Before finishing, install a waterproofing system, including a concrete vapor barrier, back-up sump pump, and French drains, which are efficient at leading water away from your house.

“Investing the money on a waterproofing system from a reputable company can be the difference between enjoying a finished space for years to come or dealing with a constant headache,” Faccone says, like installing new carpet after every rainy spring.

5. Putting down carpet

In fact, consider nixing the idea of carpeting altogether. Yes, digging your toes into soft, fluffy carpeting is so much better than walking on cold concrete. So we won’t blame you if you elect for fluff. But Eskew calls carpets a “no-no in older houses”—after all, carpet is the worst kind of flooring to salvage after a flood.

“Stick to a vinyl locking tile that can be fully removed if it were ever to get wet,” he says. “You’ll hope to never have to tear it back up, but you’ll be prepared to do so.”

6. Clinging to the wet bar

When you think of a classic tricked-out basement, chances are you’re imagining a sweet wet bar with a built-in Kegerator, plenty of shelving for all the liquor you plan to stock up on, and bar stools galore.

“While very popular, every basement does not need a built-out bar,” Bowman says.

Here’s how to know if your basement is one of the few: Will you entertain guests at your fancy wet bar often, or once in a blue moon? If it’s the latter, consider alternate entertaining areas.

Bowman recommends arranging chairs and sofas around a bar cart or cabinet.

“This is a much more comfortable than sitting at a bar on hard stools,” she says.

7. Sticking with low ceilings

You shouldn’t have to hunch to enjoy your extra space. If you have the cash for a serious renovation, consider digging out the basement.

“An additional 12 inches of height will make the basement feel more spacious,” Calamia says.

Plus, the extra room does a lot to eliminate the frightening cavernous effect so common in dark basements.

But if your budget is tight, there are plenty of ways to make small, low-ceiling rooms feel bigger. Aim lights upward, and use light, movable furniture to expand a tiny space—and create a cozy basement worthy of lazy Saturday afternoons.