Home renovations aren’t for the faint of heart. In addition to living off microwavable meals, you’ll likely have to endure construction dust, extended deadlines and hidden expenses. ‘Hope for the best and prepare for the worst’ should be every first-timer’s mantra.

Greg Stewart is the Chief Operating Officer of Bungalo, an online homebuying platform where shoppers can browse, finance and purchase professionally renovated homes in five US cities. Here he shares four renovation mistakes that delay timelines and burst budgets, complete with real dollar amounts based on the company’s extensive home flipping experience.

1. Overlooking your plumbing system

You may be able to rattle off your home’s square footage, the number of closets it has, and your kitchen countertop material, but do you know what kind of pipes exist within your walls? If your home’s pipes are leaking or deteriorating, it may be high time to replace them. “Upgrading plumbing from cast iron to PVC can cost between $2,000 and $5,000 per bathroom, with an upgrade for the entire home costing $15,000-plus,” says Stewart.

2. Applying for permits at the last minute

Many contractors will secure building permits on your behalf, however, if you’ve agreed upon an hourly rate or are going the DIY route, you may want to submit the paperwork yourself — well in advance. “In a hot real estate market, permitting can be an excessively long process,” explains Stewart. “The average permit takes up to 45 days to secure and costs buyers anywhere from $300 to $1,000-plus depending on the permits required.”

3. Not budgeting for surprises during demolition

Every renovation needs a contingency fund — an emergency cash reserve of between 10 and 20 percent of the total cost of the project. If you’ve ever watched Fixer Upper or The Property Brothers, you know unforeseen expenses are bound to arise. Stewart points to structural issues, electrical problems and roof repairs as the most expensive culprits.

“Structural issues often result in another visit to the permitting office and cost buyers at minimum a few thousand, especially when dealing with structural code like hallway dimensions and window egress, which can be upwards of $10,000,” he notes. Structural damage can be invisible to the untrained eye, so it’s best to call in the pros to conduct a thorough inspection.

Older homes built between the 1880s and late 1930s may harbor knob and tube wiring, an outdated electrical system that may pose a fire hazard. “Electrical requirements can cause an inspector to require a full home rewire which can cost over $20,000,” says Stewart. That’s no small chunk of change when all you really wanted was a bigger footprint for the master bedroom.

Roof repairs are a fact of life when you’re a homeowner. The lifespan of your roof will depend upon the material used. Asphalt shingles, for example, need to be replaced every 15 to 30 years. “New roofs are typically $10,000, but repairs like adding caps to exposed nails can be completed for a few hundred dollars,” adds Stewart.

4. Changing your mind once the renovation is underway

One thing you can control during a home renovation is your decision making process. “A customer changing their mind can cost limitless money and time,” says Stewart. “Changed plans at any time can require a new permit, which can put the job on hold. Not to mention, contractors will typically charge more for changed orders during construction.” While it might seem like no big deal to swap the ceramic tile for porcelain, you may wind up sabotaging your own budget and timeline.

4 Home Renovation Mistakes That will Cost You Time & Money by Kelsey Pudloski | Livabl