Introduction
Toronto’s weather can be tough on bathrooms. With high humidity, temperature swings, and long winters, moisture easily builds up—leading to mold, mildew, and costly damage if your bathroom isn’t properly protected. That’s why knowing how to waterproof a bathroom in Toronto’s humid climate isn’t just a good idea—it’s a must for every homeowner.
In this blog, we’ll walk you through the best ways to waterproof your bathroom from start to finish. Whether you’re doing a small upgrade or a full renovation, you’ll learn how to keep moisture out and protect your home for the long term. Let’s explore the smartest materials, methods, and tips to build a bathroom that stands strong against Toronto’s damp conditions.
Why Waterproofing Matters in Toronto’s Climate
Toronto’s humid climate creates the perfect environment for moisture to linger—especially in bathrooms. With frequent temperature shifts, condensation builds up on walls, ceilings, and floors, making these spaces highly vulnerable to mold growth, water damage, and even structural decay over time.
Properly waterproofing a bathroom in Toronto’s humid climate helps prevent these common issues. High humidity, particularly during summer and winter months, can seep into tile grout, behind walls, or under flooring if not sealed correctly. Once moisture gets in, it can lead to black mold, which is difficult to remove and harmful to your health. It can also warp drywall, damage wooden supports, and reduce the overall value of your home.
Waterproofing also helps improve energy efficiency. A well-sealed, moisture-resistant bathroom retains heat better, reduces the chance of cold drafts, and supports better indoor air quality—something especially important in older Toronto homes.
In short, waterproofing isn’t just about protecting surfaces—it’s about building a safer, longer-lasting bathroom that can handle Toronto’s challenging climate year-round.
Choosing the Right Waterproofing Method
When planning how to waterproof a bathroom in Toronto’s humid climate, selecting the right method is one of the most important steps. Not every waterproofing solution fits every space. Your choice depends on your bathroom’s size, materials, and exposure to moisture—especially in areas like showers, tubs, and floors.
1. Cementitious Waterproofing
This is one of the most popular methods used in Toronto homes. Cementitious waterproofing involves applying a cement-based coating over walls and floors to create a water-resistant barrier. Brands like Schluter® are widely recommended by professionals because they comply with the Ontario Building Code and offer long-term durability. It’s especially effective for tiled showers and floors.
2. Liquid-Applied Waterproofing Membranes
These roll-on or brush-on membranes are flexible and great for uneven surfaces or curved areas. Once dried, they form a seamless waterproof layer that prevents water from seeping into walls or subfloors. This method is often used in combination with mesh reinforcement on joints and corners to strengthen high-risk areas.
3. Sheet Membranes
Sheet membranes are prefabricated waterproof layers that are applied to flat surfaces. They’re ideal for large bathroom floors or behind wall tiles in showers. These sheets are extremely effective at stopping water penetration when properly sealed at the edges and corners.
4. Waterproof Backer Boards
Instead of traditional drywall or green boards, many professionals use waterproof cement boards behind tiles. These boards don’t absorb moisture and add an extra layer of protection when paired with a surface membrane.
Step-by-Step Waterproofing Process
If you’re wondering how to waterproof a bathroom in Toronto’s humid climate, following the right steps is key. Whether you’re doing it yourself or hiring a contractor, this process ensures your bathroom is fully sealed against moisture, mold, and long-term damage.
1. Prepare the Surface
Start by cleaning all surfaces—walls, floors, and corners—where waterproofing will be applied. Remove dust, grease, and loose particles. The surface should be dry, smooth, and free of cracks. Patch any holes before moving to the next step.
2. Install Waterproof Backer Board
Instead of regular drywall, use cement backer boards in moisture-prone areas like the shower or tub surround. These boards are mold-resistant and ideal for humid environments like Toronto.
3. Apply Primer (If Needed)
Some waterproofing systems, especially liquid-applied membranes, require a primer before application. This helps the membrane adhere properly and last longer.
4. Apply the Waterproofing Membrane
Use either a liquid waterproofing membrane or a sheet membrane like Schluter® KERDI. Start from the bottom and work your way up the walls. Pay close attention to corners and joints—these are common leak points.
- For liquid membrane: Use a roller or brush to apply two coats, allowing proper drying time between each.
- For sheet membrane: Embed the sheets into thin-set mortar and press firmly to eliminate air bubbles.
5. Seal All Joints and Fixtures
Use waterproof tape or banding to seal all seams, edges, and around plumbing fixtures. In Toronto’s damp climate, these areas are prone to leaks if not sealed correctly.
6. Let It Cure and Test for Leaks
Allow the membrane to fully cure—usually 24 to 48 hours depending on the product. Once dry, perform a flood test by filling the shower base with water and checking for leaks. This step is especially important if you’re waterproofing a curbless shower.
7. Tile Installation
Once everything is dry and tested, you can begin tiling. Use waterproof grout and seal the grout lines once cured for added protection.
Best Materials & Local Considerations
Choosing the right materials is crucial when planning how to waterproof a bathroom in Toronto’s humid climate. With moisture being a year-round concern, every layer in your bathroom—from the walls to the flooring—should be designed to resist water damage, mold, and decay. Let’s explore the best waterproofing materials and what to consider specifically for homes in the Greater Toronto Area (GTA).
1. Waterproof Backer Boards
For walls behind showers and tubs, always use cement backer boards like Durock or HardieBacker instead of drywall or green board. These boards are mold-resistant, non-organic, and won’t degrade over time. They’re ideal for humid climates and help support tile without absorbing moisture.
2. Membranes (Sheet & Liquid)
Toronto professionals often recommend Schluter® KERDI or RedGard for dependable waterproofing. These membranes:
- Create a watertight seal
- Are approved by Ontario building codes
- Work well with tiled floors and walls
Use sheet membranes for wide coverage on walls and floors, and liquid-applied membranes in tight or curved areas.
3. Sealants and Caulking
For joints, seams, and around fixtures, choose a 100% silicone caulk or a high-grade hybrid sealant. These prevent water intrusion where tiles and materials meet, especially near tubs, faucets, and shower corners.
4. Waterproof Tile Adhesives & Grout
Always use thin-set mortar approved for wet areas. For grout, opt for epoxy grout or a grout with waterproof additives. Don’t forget to seal your grout annually to keep it resistant to stains and moisture.
5. Ventilation Systems
Toronto’s cold winters and humid summers demand strong ventilation. A quiet, high-capacity bathroom fan (rated for the room size) helps pull out moisture and prevents condensation from settling on surfaces. Some advanced fans even come with humidity sensors.
Toronto Code Requirements & Permits
When learning how to waterproof a bathroom in Toronto’s humid climate, it’s important to understand that some waterproofing and renovation work may require permits under local building codes. Following these regulations ensures your bathroom upgrade is safe, legal, and up to standard.
1. When Is a Permit Required?
In Toronto, you typically need a building permit if your bathroom renovation involves:
- Modifying the structure or layout (like moving walls)
- Adding or relocating plumbing fixtures
- Installing or altering waterproofing systems in a shower or wet room
- Changing floor drains or venting systems
For waterproofing projects—especially if you’re renovating a curbless shower, relocating a tub, or installing in-floor heating—permits help ensure your work meets city safety and moisture-control standards.
2. Plumbing & Waterproofing Oversight
According to the Ontario Building Code, waterproofing and plumbing work must be inspected by a certified building inspector. This helps verify that:
- Waterproof membranes are installed correctly
- Shower slopes are adequate (minimum 2% gradient)
- There are proper barriers to prevent leaks into adjacent rooms
Working with a licensed contractor who understands Toronto’s inspection process can help avoid delays or costly rework.
3. Permits for Condo Renovations
If you’re waterproofing a bathroom in a Toronto condo, you’ll also need approval from your building’s condo board or property management. Condo rules may require:
- Pre-approval of waterproofing materials
- Proof of contractor insurance
- Scheduled inspection times
4. Who Can Apply for a Permit?
You can apply for a building permit through the City of Toronto’s ePlan portal. However, it’s often easier and faster to have your licensed contractor submit the application on your behalf.
Maintenance Tips for Long-Term Results
Even after you’ve successfully waterproofed your bathroom in Toronto’s humid climate, ongoing maintenance is key to keeping it protected. Regular upkeep not only extends the life of your waterproofing system but also helps prevent mold, mildew, and moisture damage over time.
1. Use an Effective Ventilation System
Install and regularly clean a high-quality bathroom exhaust fan. This helps remove excess moisture after showers, especially during Toronto’s humid summers and cold winters when condensation builds up. Always run the fan for at least 20–30 minutes after bathing.
2. Reseal Grout and Caulking Annually
Grout and caulking naturally wear down over time, allowing moisture to seep through. Use a silicone-based sealant to reseal corners, joints, and tile grout at least once a year. In high-moisture areas like curbless showers or near tubs, more frequent resealing may be needed.
3. Check for Signs of Mold and Peeling
Regularly inspect corners, baseboards, behind toilets, and under vanities. If you notice mold spots, peeling paint, or musty smells, take immediate action. Early detection can help you avoid serious structural problems later.
4. Clean Tiles with Mold-Resistant Products
Use mild, mold-resistant cleaners on tiles and grout lines. Avoid harsh chemicals that can degrade waterproof membranes underneath. A simple vinegar-water solution or specialized bathroom cleaner helps maintain cleanliness without damaging surfaces.
5. Keep Wet Areas Dry
Wipe down glass panels, shower floors, and walls after use. Install squeegees or microfiber cloths for daily users. This habit prevents water buildup and slows down wear and tear on waterproof surfaces.
Conclusion
Knowing how to waterproof a bathroom in Toronto’s humid climate is essential for creating a healthy, long-lasting space. With the right materials, proper techniques, and code-compliant methods, you can protect your home from mold, mildew, and moisture-related damage. Whether you’re installing a curbless shower or upgrading a traditional tub area, waterproofing ensures safety and durability. By using quality membranes, sealing joints properly, and maintaining ventilation, you’ll keep your bathroom dry and damage-free year-round. Don’t overlook the importance of local code requirements and regular maintenance—they’re just as vital as the initial installation. A well-waterproofed bathroom in the GTA adds comfort, peace of mind, and long-term value to your home.
Frequently Asked Questions (FAQs)
1. What is the best way to waterproof a bathroom in Toronto’s humid climate?
The best way to waterproof a bathroom in Toronto is to use a combination of cement backer boards, waterproof membranes (like Schluter® or RedGard), and silicone caulking. These materials resist mold and moisture while meeting Ontario building codes.
2. Do I need a permit to waterproof my bathroom in Toronto?
You may need a permit if your waterproofing project involves plumbing changes, moving walls, or building a curbless shower. It’s best to check with the City of Toronto or work with a licensed contractor who can guide you through the permit process.
3. How can I prevent mold in my Toronto bathroom?
To prevent mold, install a high-efficiency ventilation fan, reseal grout annually, and wipe down wet surfaces regularly. Proper waterproofing combined with good airflow is key to controlling humidity in Toronto homes.
4. How long does waterproofing last in a bathroom?
When installed and maintained properly, a waterproofing system can last 10–15 years or more. Annual inspections and resealing high-moisture areas help extend its lifespan, especially in humid environments like Toronto.
