Taking on a home improvement project is expensive enough as it is – why add to the bill? Whether you’re fixing a leaky faucet or remodeling an entire bathroom, here are some costly mistakes to avoid.

Skipping Less Glamorous Improvements

It’s crucial to take care of structural issues before starting on cosmetic fixes. We all want a beautiful kitchen and a stylish bathroom, but if you sink $26,000 into a new kitchen when the roof above it has a leak, you might find your custom cabinets destroyed after a series of bad storms. It’s not as exciting or Pinterest-worthy, but the stuff you don’t see — pipes, wiring, framing, and more — is usually the most important.

Failing To Get Multiple Quotes and Vet Contractors

You’ve heard it a million times, but it’s still true: Get at least three bids for a project, and make sure the contractors you choose are licensed, insured, and in good standing with the Better Business Bureau.

This Old House recommends getting recommendations from friends, neighbors, lumber yards, or your town’s building inspector, or combing review sites like Angie’s List. Then call contractors on your short list and ask them questions. Some queries seem like overkill — I wouldn’t even know what to do with a financial reference if I got one, for example — but others will give you a good sense of what kind of company you’re working with. How many projects are they juggling? (The more jobs they take on at once, the more likely you’ll end up with delays.) Do they use subcontractors, and how long have they worked with them if so?

Then choose at least three to come give you an estimate in person. This also functions as a test of how well you communicate with each other. Make sure they’re responsive in your preferred medium, whether that’s by text, email, phone, or in person, so you’ll stay on the same page throughout the job. Their quote should be itemized and specific about the scope of work.

And getting multiple bids isn’t just about shopping around for the best price. It will ensure you don’t overpay, but a lot of experts say homeowners should be wary of going with the lowest bid. “The lowest bid never equals the best job,” Property Brothers’ Jonathan Scott told HGTV.com. “Some give cheap quotes just to get the job, then tack things on or cut corners and install low-quality products.”

What’s more, while some projects are pretty straightforward — a roof is a roof — there’s often more than one way to do a complex job, and soliciting other opinions can be valuable.

When we remodeled our bathroom two years ago, it involved shuffling the layout around so we could squeeze in a stackable washer/dryer. We were tempted to go with the first quote we got – from a friendly, capable guy who offered to do the work at a reasonable price. But the second contractor came up with an ingenious design solution that the first hadn’t. While they had a better (and more expensive) reputation for doing quality work, their quote was actually lower than the first guy’s, all because they figured out a more efficient way to accomplish the same thing.

Playing it By Ear

It’s tempting to toss in some of the extra items on your wish list while you’ve got a contractor in the house, and sometimes it can make sense — but it’s always going to cost you more money. If you’ve got a bunch of items on your house to-do list, get them all written into the project estimate from the start, and stick to your plan as much as possible.

“When a homeowner wants to stay on budget, I tell them, ‘Look, the only way you’ll stay on budget is if the day I start is the day you leave the site and you don’t come back until I’m done,” said Tom Silva, general contractor on This Old House. “Because if you’re here, you will make a change.”

Remodeling is contagious: As soon as you make one improvement, the rest of the house can look drab by comparison. “Then all of a sudden it’s, ‘This room looks so nice, let’s paint the other room,” Silva said. Try to avoid that temptation.

Attempting A Complex DIY on a Weekend or Holiday

Here’s a dilemma : For most DIY’ers, the weekend is often our only chance to hit the hardware store and tend to whatever time-consuming home improvement project we’ve had on our minds.

The trouble is, if it’s a particularly challenging task and something goes wrong — say, the new pipe fitting you installed won’t stop leaking — and you need to call in a pro, they’ll likely charge you emergency rates (perhaps double the usual price) to come help you out. And that’s if you can find someone at all — if it’s Christmas break or July 4th weekend, you could be waiting for a while.

For more difficult DIY projects, I usually take a day or two off work, and sometimes even send the rest of the family packing in case things get ugly. If that’s not an option, I’ve come to accept that hiring a pro makes more sense in those situations. “There’s a lot of plumbing you can do yourself,” This Old House host Kevin O’Connor told me. “But if the water has to be shut off, do you want to be out of water for a weekend?”

Biting Off More Than You Can Chew

Along those lines, tinkering with your home can quickly spiral out of control, and sometimes there’s no going back once you open up a wall and discover the surprises within. From mold to rotted-out studs to faulty wiring, there’s no telling what could be waiting for you when you begin even a seemingly simple job. So make sure you have enough time built into the schedule — and money in the bank — to finish what you start. Whatever you’re anticipating, Silva said, “It’s going to take you longer, and it’s going to cost you more.”

And if you’re tackling the work yourself, make sure you’re up to the task as well as any possible complications, lest you get in over your head — or even put yourself in danger. “You gotta know your qualifications,” says Silva. “If you don’t know anything about electricity, don’t touch it. If you know a little bit about electricity? Don’t touch it,” he said. “Leave that to a pro or you’re going to burn your house down.”

Skipping the Building Permit

Pulling a permit from your city or town — and waiting for the inspector to come by and check the progress — can be kind of a pain in the ass. But if a permit is required (it varies by community and the scope of the job), this is an essential step.

For one thing, those inspections are designed to protect you from shoddy or unsafe work. But what’s more, your homeowners insurance could potentially deny a claim if unpermitted work creates a problem, or you could face trouble when it’s time to sell your home. And if you get caught doing major work without a proper permit, the city could issue a stop work order – leaving you with indefinitely exposed studs – or even force you to rip out newly installed fixtures so inspectors can check the electrical and plumbing work, and then start all over again.

Ignoring Safety Precautions

It’s oh-so-tempting to skip the protective eye goggles when you’re cutting a board or to forego a HEPA mask even though you’re working with potentially hazardous materials. But any time or money saved by ignoring basic safety precautions isn’t worth a costly emergency room copay or long-term health issues.

Anytime you take on a home improvement project, it’s bound to be more expensive than you thought. The least you can do is avoid making unforced errors that can make it even pricier.

Don’t Make These 7 Costly Home Improvement Mistakes by Jon Gorey | Apartment Therapy