DIY Disasters: 20 Repairs to Leave to the Pros

Home improvement looks so easy on TV, and going the DIY route is a real money saver when facing labor costs that can turn a leaky $11 toilet fill valve into a $200 expense. However, some projects are dangerous and easy to screw up no matter how many YouTube videos show the way, and many renovations require permits and finished work that must meet code. Sometimes it's better to hire a professional.

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Andrew Lisa contributed to this story.

Few household projects have a smaller margin for error — a single wrong move or momentary lapse in concentration can be fatal. Most municipalities require that a licensed professional, with knowledge, training, and insurance, do serious wiring and electrical work. Permits are required, and the work must be done to code to pass inspection. The United States has some 45,000 electrical fires a year, according to the National Fire Protection Association, and amateurs risk injury. 

Check sites like Thumbtack and TaskRabbit to find professional services and home improvement helpers in your area.

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It's fine to DIY simple repairs involving faucets and toilets. But turn to a professional for tasks such as replacing a hot water heater or installing new pipe, because of the required permits, safety regulations, and associated risks, from water damage to carbon monoxide emissions. One plumber wrote on the site Angi, "We encounter improperly installed water heaters on a daily basis." Licensed plumbers have years of training and proper tools, and work to code. 

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A skilled homeowner can do much of a bath renovation, as long as the footprint of the room is the same and no wiring or plumbing needs moving. Upgrades such as replacing a shower head or adding a handheld shower are easy, but fancier fixtures need extra water supply lines, thermostatic controls, drainage, and other systems behind walls that are beyond the skills of most DIYers. 

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Fixing a broken thermostat is easy, as is changing a filter or unclogging a drain line, specialists say, but repairing or replacing an HVAC system is not. Repairs gone wrong can cause serious damage — such as freon leaks — and manufacturers can void their warranties if someone besides a licensed professional works on the system.

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There are just two steps to refinishing a tub: sanding and spray painting. But when pros show up in hazmat suits, it's easy to see this isn't a job for homeowners. Professionals have access to sanders meant specifically for tile, and the acrylics they use last longer than anything from a big-box store. Pros also have a wider selection of colors and know how to ventilate a room and speed the curing process.

Some window fixes involving weather stripping, gaskets, caulking, and screens are fine for DIYers to tackle. But imprecise window installation can result in leaks that cost more in energy inefficiency than professional installation would have cost to begin with. Adding a skylight means not only cutting through the roof but installing flashing, and usually must be done by a roofer. With both, failure to follow the manufacturer's instructions can void the warranty. 

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Natural gas is potentially explosive and poisonous, so this is a job best left to professionals. When switching to a gas stove from electric, for example, a plumber should handle the installation of piping and an electrician is needed to modify the circuit. The work also must meet code. 

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Leaks can be caused by ice dams, cracked caulk or flashing, or actual holes, but remember that water travels, so the area of water damage might not be where the leak is. Finding the cause and location can be difficult — and dangerous. Roofing is one of the deadliest jobs in America, according to fatality rates from the Bureau of Labor Statistics, and the Occupational Safety and Health Administration has identified falls as the leading cause of death among construction workers. Experts can identify the source of a leak quickly and spot damage that might cause problems in the future. 

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Homeowners who find flooding in their basements often apply waterproofing paint or try sealing cracks in the concrete. Experts at Angi warn that these DIY repairs usually provide only temporary relief. Permanent solutions might involve digging an 8-foot-deep trench; jackhammering a concrete floor to install drainage, piping, and a sump pump; installing a French drain or special tiles; and adding a waterproof membrane to the exterior. Go to a pro. 

Trees that have died or been damaged by fierce weather can threaten houses and cars. Tree removal is a job for a certified arborist or similar expert, because it's perilous work — just go to YouTube and search "tree felling gone wrong." The tools used to remove trees are dangerous, not least of them the ladder. More than 300 people die and 500,000 are injured using ladders every year in the United States, according to the National Institute for Occupational Safety and Health. Arborists use tree cranes to get up high, carry insurance to protect property from falling branches, and know the art of pruning. 

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Many older homes have asbestos insulation, floor tiles, siding, or pipe wrap that can be disturbed and become toxic when walls are opened up, risking a family's health. The only way to know for sure if asbestos is a risk is to have a professional do a test. The EPA strongly suggests hiring an asbestos abatement specialist with specialized tools and ventilation equipment. 

Homeowners can remove mold themselves from the outside of walls, usually with some kind of bleach solution — as long as they wear protective gear such as a high-filtration face mask and gloves. If mold is extensive and inside the walls, call an expert to seal off the area, so spores don't travel; use a chemical treatment to prevent mold from returning; and clean out air ducts or the HVAC system. If necessary, they can also replace drywall and do other restorations.

Related: What You Don't Know About Mold Can Ruin Your Life

Lead paint is no longer legal, but homes built before 1978 are likely to have it. When it begins to crumble or flake off, such as during renovation, it creates a toxic dust. Many states require that paint be removed by a certified lead paint specialist, who can determine an abatement strategy and remedy the situation, either by covering the surface with a special paint, enclosing it with drywall, or removing it entirely. 

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Hardwood refinishing isn't difficult, but it's difficult to do well. It involves a drum sander, a special edger, a floor polisher, stain, and poly, and there's a big difference between the equipment you can rent and the bigger, more powerful stuff the pros use. You're likely to gouge the floor with a rented sander, which weighs more than 100 pounds and can move on its own, and staining magnifies any mistakes. 

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On most home renovation shows, the hosts begin work by merrily whacking at walls with a sledgehammer. What you don't see: Off the air, a structural engineer examines the walls first to make sure they aren't load-bearing. There could be all kinds of things hidden in the walls, as well, particularly in an older house. Pros will recognize asbestos and stop as soon as they see it. Another thing they don't show on TV: the cost and hassle associated with removing debris.

Home improvement stores sell products for removing creosote deposits from chimneys, but they're not a substitute for professional cleaning with the right tools — and DIYers might not catch problems in masonry, spot animal nests, or identify issues with flashing or trim. Pros can recommend the most efficient way to use a wood stove or fireplace and do a qualified inspection to avoid one of the more than 22,000 chimney fires a year cited by the Chimney Safety Institute of America.

A fresh coat of paint is one of the cheapest and simplest ways to radically overhaul your house — on the inside, that is. For the part of your house that stands between you and the elements, however, things get tricky. Exterior painting requires critical and complicated prep work; with stucco, it can take the better part of a month. If you don't want a peely, bubbly surface, precision spraying and backrolling is required — and that precision comes only with experience.

This one falls into the "looks easy but actually isn't" category. A skilled, experienced crew can pave a driveway in a single day. Most homeowners cannot. If it rains overnight while you're half-done, you — and your partial driveway — are in trouble. Putting in a driveway is a labor-intensive affair, and the surface is likely to crack, shift, crumble, or come out uneven unless left to a pro. 

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Garage doors and openers are surprisingly complex. Tinkering with them yourself is likely to result in irreparable damage to the garage door — and possibly to you. It also requires specialized, expensive tools that you're almost certain never to use again.

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When you see cracks in your home's foundation, walls, or floors, or if doors and windows start sticking, it's likely you have foundation issues. If you're flirting with the idea of shoring up joists or load-bearing joints yourself, don't. Mistakes can affect plumbing, electrical work, and other major systems.