9 Home Renovations That Can Cost Far More Than Homeowners Expect, Especially When Plumbing, Electrical Work, Or Permits Get Involved

Every renovation starts with a pretty picture and a tidy number. Then the contractor opens a wall, and the number starts to wiggle.

A room under renovation with a ladder and buckets of paint beside an unfinished wall.

A Homes.com article by Dave Hansen, “7 hidden costs of home renovations and how to avoid them” (July 22, 2026), lays out where the surprises tend to hide. It says its estimated pricing comes from the home services marketplace Angi.

We pulled nine of those cost areas into one list, with the price ranges the article gives. Your own quote will depend on your region, your house and the contractor, so treat these as ballparks and not promises.

Water Damage Hiding Behind The Drywall

Homes.com puts water damage repair at $1,350 to $6,300. It sits under the “structural issues” heading, and it is the kind of problem that stays out of sight until the demolition starts.

That is why a leak you never noticed can quietly add thousands to a bathroom or kitchen project.

Termites And Pests That Chewed Up The Framing

The article lists termite and pest damage repair at $1,000 to $10,000. That is a wide range, and the spread depends on how far the damage runs.

Wood that looks fine on the surface can be a different story underneath, so ask your contractor to look closely before the project is priced.

A Foundation Problem Nobody Planned For

Foundation repair runs $2,225 to $8,135 in the Homes.com article, and major full-structure repairs can exceed $25,000.

It is the sort of discovery that can change the whole project. A kitchen update is one thing; fixing what holds up the house is another.

An Electrical Panel That Cannot Handle The New Load

New appliances and lighting can ask more of your wiring than the old panel can give. Homes.com lists an electrical panel upgrade at $518 to $2,191, with an average of $1,345.

The cost can climb to $4,500 with a breaker box replacement, panel relocation or amperage expansion, according to the article.

A Main Water Line That Leaks Just When You Open Up The Floor

Plumbing surprises are common in remodels. The article puts main line water leak repair at $600 to $4,500.

It also lists smaller plumbing items, like faucet or fixture replacement at $150 to $600 and a new water heater installation at $800 to $2,000. Those small items add up.

Plumbing and electrical work are also two of the areas Redfin says usually trigger permits. That means the pipe fix and the permit fee can show up on the same invoice.

A Heating System That Gives Out Mid-Project

Homes.com lists a new heating system at $3,800 to $7,500. A new air conditioning system is $2,600 to $6,200.

If the old system is struggling, a remodel can be the moment it finally quits. Ask for its age and condition early.

Homes.com also lists insulation at $0.30 to $6.75 per square foot, depending on the material. When a project opens up an attic or wall, the choice of material changes the total quickly.

Permit Fees That Land On Your Bill

The article says typical permit fees range from $525 to $3,114. That is a real line item, and one many homeowners forget to add.

It is also a good reason to ask any contractor, up front, who pulls the permits and who pays for them.

A Redfin guide to building permits says structural work, electrical rewiring, plumbing changes and HVAC installs usually need a permit. It also lists fines, stop-work orders and forced demolition of unpermitted additions as possible consequences of skipping one.

Redfin adds that many buyers avoid homes with unpermitted work, which can complicate a sale. Local rules differ, so your city or county building office has the final word.

Asbestos Found In An Older Home

Asbestos removal runs $1,215 to $3,278 in the Homes.com piece, and disposal of the material is listed at $10 to $150 per cubic yard, varying by state.

Older houses are the usual suspects. If your home is from an earlier era, ask for testing before demolition starts.

Knob-And-Tube Wiring Inside The Walls

Here is the budget buster. According to Homes.com, knob-and-tube wiring removal costs $12,000 to $36,600.

That is a huge number, and a good reminder to have the wiring checked before anyone swings a hammer.

Homes.com recommends setting aside a contingency fund of 10% to 20% of the total project cost. For do-it-yourselfers, it suggests budgeting about 10% above estimated material costs for price changes.

Think of it as an insurance policy you hope not to use. If the walls turn out to be clean, you keep the money for the next project.

Waste adds up too. The article lists a standard waste truckload at $300 to $800.

The Homes.com list covers only part of the picture, but it shows the pattern. The costly surprises tend to hide in the places nobody can see until the project is underway: behind walls, under floors and inside the electrical panel.

Get several written quotes, ask exactly what each quote covers, and keep your cushion untouched until you need it. A little planning now keeps a bright new kitchen from becoming a sour memory.

Willow and Hearth