8 Hidden Bathroom Problems You Shouldn’t Ignore

contemporary bathroom with recessed bath under large window

Whether you’re looking to buy a new home or renovating your own, you’ll likely notice property damage and construction issues. Problems pop up all over the house, but the most common are bathroom problems. Faulty old plumbing, water damage, poorly installed flooring… a lot can go wrong in one room! Here are some hidden bathroom remodel mistakes to repair before they drain your wallet. 


Water is everywhere in the bathroom and so is sealant and protection… at least we would hope. Poor or missing caulking is one of the most common bathroom problems to run into, and it’s a doozy. Water can leak into cracks or areas missing caulking, not only causing water damage but also mould growth. If you run into a smelly toilet, check the caulking – it’s likely the issue. Here are some easy spots to check. 

  • Showerhead flange and plumbing. There should be caulking around the outside of the showerhead flange and on the plumbing attached. 
  • Toilet. With this fixture, the Building Code doesn’t have any guidance. Most plumbers caulk between the toilet base and the floor for added stability when the floor is uneven. However, if you end up caulking it and your toilet springs a leak, the water may end up in your floor rather than on it, making it harder to notice.
  • Shower/tub. If you’ve got a shower or tub, check if the spaces where it meets the floor and wall are caulked. 
  • Vanity. The space between the vanity countertop and the wall should be caulked to prevent water from seeping into cracks. 

hidden bathroom problems culking grouts with mould

Plumbing problems 

Sinks, showers, baths… they all need water, so pipes are everywhere. And, unsurprisingly, they cause many of the biggest bathroom problems.  

Most modern plumbing uses copper, but if you have an older home, you might run into cast iron, galvanized steel, or even lead pipes. Iron and steel piping aren’t nearly as corrosion resistant as copper, so you might want to replace them to avoid premature leaks or bursts. That said, lead pipes can cause serious health consequences, so they should be replaced immediately. Many cities, including Toronto, offer grants to offset the cost.

Need to repair parts of your plumbing system? In just a few clicks, find a specialized contractor to carry out maintenance and repair work through the HomeExpress online referral service.

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Aside from leaks and water damage, other plumbing issues can be hard to detect. A maze of pipes could be hiding behind your drywall. Sometimes you’ll find pipes that lead to nowhere, perhaps a fixture that was planned but never completed, or old pipes that were left during a previous installation. If you come across excess pipes during your renovation, have your contractor remove them.

contractor tacking care of pipes for plumbing

Poor drainage 

Unless you want your bathroom trips to be punctuated by wet feet, good drainage is key. Each main fixture has its own drain and trap, which can become clogged with things like hair over time. Many homeowners reach for drain cleaner to solve this, but the caustic fluid can cause bigger bathroom problems down the line and even damage pipes. If you can access it, empty the pipe trap and run the water through until it’s clear. Otherwise, you’ll want to clear it manually or hire a licensed plumber.
Sometimes you’ll find drains installed in the wrong place or improperly, which tends to leave pools of water in places like your shower. The flooring or shower pan is supposed to be slanted slightly toward the drain, but sometimes faulty flooring or a previous botched shower conversion can prevent it. No matter the cause, you’ll want to correct these bathroom remodel mistakes to avoid water damage.  

bathroom floor drain being cleaned to avoid hidden bathroom problems

Breath of wet air 

Excessive humidity can lead to water damage like bubbling or peeling paint and create the perfect environment for mildew and bacteria. A quick way to check if you have this bathroom problem is to look at your mirror after a shower: if the fog sticks around, then it’s time to test your ventilation. In a full bathroom, a lone window isn’t enough: it needs a fan. 

If you have a fan, test it by putting a piece of toilet paper up to it while it’s running. If it can’t hold the paper in place, then its probably not working properly. And, even if it can hold the paper, you may need a fan with a higher volume flow if you still have humidity stagnating in your bathroom. 

humid bathroom mirror with dripping fog

Hidden water damage 

Mildew, mould, and even rot could be hiding behind your tiles and walls. This bathroom problem is typically caused by water infiltration, but fixing the source of the leak isn’t enough – you need to address the damage, as well. Over time, mildew will turn to mould, and rot will eventually compromise the structure of your home. Here are some signs of water damage to look out for. 

  • Discolouration 
  • Bubbling and cracking paint 
  • Water accumulation/puddles 
  • Soft drywall 
  • Musty smells 

If you see any of these issues, or if there was a known leak, have a professional check your bathroom for water damage. Things like mouldy insulation will need to be replaced immediately (mould is almost impossible to get out, and it’ll spread), while mouldy wood will need to be treated and sealed to prevent future rot.

ceiling with peeled paint because of water damage

Faulty wiring  

From the pendant lights and sconces to the plug-in towel warmer, a lot of elements in your bathroom are connected with wires. Your electrical fixtures might seem like they’ve been installed properly at first glance, but there are often flaws hiding just below the surface. 

The easiest bathroom remodel mistake to notice is a lack of outlets in your main bathroom. While a single GFCI outlet isn’t necessarily a big deal, it can be really inconvenient if your toothbrush or shaver charging station needs to be plugged in at all times. Other common bathroom remodel mistakes include overloaded outlets, improper grounding, and bare wires, which can be fire and electrocution hazards. 

If you’re updating an older home, take a moment to check if the switches and outlets are properly grounded. Turn off the power to your bathroom, then remove an outlet cover and see if there’s a bare wire attached to nearby metal. This grounds your electrical, and if your bathroom lacks it, it’s a good idea to hire an electrician to install one. While they’re there, they can check for other signs of faulty outlets. 

wires hanging outside their outlet

Unsafe flooring 

We’re all accustomed to the creak of a floorboard or uneven tiles, but these seemingly innocuous flaws can be indicative of much bigger bathroom problems. Due to the weight of fixtures and tiling, the bathroom floor can often end up bent out of shape. For tile floors this means cracking tiles and grout, leaks, and even collapsing floors. 

In older houses, you might find a web of pipes in the floor reaching fixtures and drains. Contractors often cut holes and notches into the joists, removing solid obstacles and helping the pipes get to where they need to go. Even though it’s a common practice, it’s possible to remove too much material from the joists, which can lead to structural instability.  

Here are some signs that your flooring might need some work: 

  • Cracked grout or tile 
  • Uneven tile 
  • Moving or soft spots in your floor 
  • Warped flooring 
  • Small holes in wood panelling (could be a sign of carpenter ants) 

cracked beige bathroom floor tiles

Material mishaps 

The bathroom is a special case for building materials – with such high moisture levels, everything needs to be sealed or protected. This means opting for water-resistant drywall, vapour barriers, mildew-resistant paint, and of course silicone caulking. Older houses typically don’t have these items, so if you’re going to invest in a bathroom remodel, you can replace all of them to prevent future issues like leaks and mould. Here are some signs that your bathroom might need an upgrade. 

  • Drywall isn’t water resistant 
  • Lack of vapour barrier between the drywall and insulation 
  • Peeling or bubbling paint 
  • Grout attaching tubs or toilets to the floor 

bubbles in paint of a bathroom wall

Wash away renovation worries 

When planning to purchase a home or renovate an existing space, many bathroom remodel mistakes can catch you by surprise. Whether it’s poorly done caulking or structural damage, you can save yourself a lot of problems by taking a look around or getting an inspection done.

If you’re ready to take the plunge, our Verified Contractors can help bring your dream bathroom to life. Otherwise, feel free to browse some of our bathroom decor ideas, completed projects, and cost saving tips. 

Briar Von Gerl is an engineer, inventor, and artist, and her favourite pastime is creating things. She applies her previous millwork design and creative experience to her writing, hopefully inspiring others to create something themselves.