You're in the middle of a bathroom remodel, everything's going perfectly, until you notice it - the bathtub lip sticks out too far. This frustrating issue affects 30-40% of alcove bathtub installations and can stop your project in its tracks. The protruding flange creates an awkward gap between your backer board and tub, threatening both the appearance and waterproofing of your finished tile surround.
The good news? This common problem has several proven solutions that don't require replacing your tub. As someone who's helped countless homeowners navigate this exact issue, I can tell you that understanding the right approach based on your specific measurements makes all the difference between a professional finish and a DIY disaster.
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This guide will walk you through four proven methods to fix a bathtub lip that sticks out, from simple shimming techniques to complete wall modifications. We'll cover everything from proper measurement techniques to waterproofing considerations, ensuring you achieve a watertight, professional-looking finish that lasts for years.
Before diving into solutions, it's essential to understand your tub's exact dimensions and installation requirements. I recommend checking our comprehensive bathtub dimensions guide to familiarize yourself with standard measurements and identify any anomalies in your specific installation.
Proper assessment is the foundation of a successful solution. I've seen homeowners waste hundreds of dollars on wrong materials simply because they misjudged their tub's protrusion. Taking precise measurements at multiple points along the tub flange will determine which solution method will work best for your specific situation.
Start by measuring the gap between your wall studs and the tub flange at several points - typically at the corners and every 16-24 inches along the walls. You'll likely find variations that range from 1/4 inch to 3/4 inch, which is completely normal. These measurements will guide your solution selection, with smaller gaps (under 1/4 inch) often requiring different approaches than larger protrusions.
For accurate measurements, you'll need a quality tape measure, level, and carpenter's square. Place your measuring tool perpendicular to the wall to get the true depth of the protrusion. Don't rely on visual estimates - I've learned that even experienced professionals can misjudge gaps by 1/8 inch or more, which can significantly impact your chosen solution.
Document all measurements in a simple sketch of your tub layout. This reference will be invaluable when selecting materials and planning your installation approach. If you're unsure about measurement techniques, our detailed guide on how to measure a bathtub properly provides step-by-step instructions with illustrations.
Furring strips offer the most versatile and cost-effective solution for protruding tub lips. This method involves attaching thin wood strips to your wall studs to build out the surface, allowing your backer board to sit flush with or slightly above the tub flange. I've used this approach successfully in bathrooms where the gap varies from 1/4 to 3/4 inch along different sections.
The beauty of furring strips lies in their adjustability. You can select different thicknesses (typically 1/4, 3/8, or 1/2 inch) based on your measurements, and even combine strips for custom depths. This flexibility makes them ideal for older homes where wall framing might be inconsistent or where the tub sits unevenly in its recess.
Installation requires basic carpentry skills and tools: a saw, measuring tape, and screws or nails. The key is ensuring all strips are perfectly aligned and secured to create a uniform surface. I recommend using construction adhesive in addition to mechanical fasteners for extra stability. This method typically costs $20-50 in materials and takes 2-4 hours to complete, making it an accessible option for most DIY homeowners.
When your tub protrusion is consistent along all walls, switching to thicker backer board provides a clean, professional solution. Standard 1/2-inch cement board creates a 1/4-inch gap above the tub flange, but 5/8-inch or 3/4-inch options can bridge larger gaps while maintaining structural integrity.
I've found this approach particularly effective in newer construction where measurements are consistent but the tub simply sits too far from the studs. The thicker board eliminates the need for transitions between different materials, creating a seamless surface for tile installation. DensShield, a gypsum-based backer board, offers 1/2-inch thickness with the added benefit of matching drywall dimensions, making transitions to adjacent walls virtually invisible.
Cost considerations are important here - thicker backer boards typically run $15-25 per sheet compared to $10-15 for standard 1/2-inch options. However, when you factor in the labor savings from not having to install furring strips and create transitions, many professionals consider this the premium solution for consistent gaps.
Sometimes the simplest solution is to address the root cause by adjusting the tub's position. If you have access to the tub's mounting points and the plumbing allows for movement, sliding the tub closer to one wall can balance out the gap distribution. I've seen this work beautifully in situations where the tub was centered too far from one wall, creating a massive gap on one side while being nearly flush on the other.
This approach requires careful assessment of your drain connection and overflow pipe. You'll typically have 1-2 inches of play in the plumbing connections, which might be enough to significantly improve your gap situation. Before attempting this method, I recommend taking photos of your current plumbing setup and consulting with a plumber if you're unsure about the connection types.
The process involves loosening the tub's mounting brackets, gently sliding it into the desired position, and then resecuring everything. This method costs nothing in materials but requires significant labor and plumbing knowledge. It's best attempted during initial installation before surrounding walls are finished.
For complex situations with varying gap sizes, a layered approach combining multiple materials often provides the best solution. This might involve using thinner furring strips in some areas combined with strategic backer board placement or even adding a layer of thin cement board over standard thickness in problem areas.
I've successfully implemented this method in older homes where wall framing is inconsistent and tub placement was done years ago. The key is creating gradual transitions rather than abrupt changes in wall depth, which can cause tile installation problems and visible step-offs in your finished surface.
This approach requires careful planning and might increase material costs by 20-30%, but it provides the most flexible solution for challenging situations. The layered method is particularly useful when you're working with existing tile and need to match surrounding surfaces without completely demolishing the bathroom.
Regardless of which solution you choose, proper installation technique is crucial for long-term success. I've developed these steps from years of experience and feedback from both DIY homeowners and professional contractors.
Waterproofing is the most critical aspect of solving bathtub lip issues. I've seen too many beautiful tile jobs fail because the gap between tub and backer board wasn't properly sealed. Water infiltration behind tile can lead to mold growth, structural damage, and costly repairs that far exceed the initial solution cost.
The gap between your backer board and tub flange should never exceed 1/4 inch. If you have a larger gap, fill it with backer rod before applying your waterproofing membrane. For gaps over 3/8 inch, I recommend using a two-part approach with backer rod followed by silicone caulk, then overcoating with a waterproofing membrane.
RedGard and Kerdi Band are the two most reliable waterproofing membranes for this application. RedGard is a liquid-applied membrane that's easy to work with and costs about $60 per gallon. Kerdi Band is a fabric membrane that costs slightly more but provides superior protection in problem areas. Whichever you choose, apply it according to manufacturer specifications and embed mesh tape for reinforcement.
Remember that the tub flange itself is designed to be the primary water barrier. Your waterproofing membrane is secondary protection. Never place backer board over the tub flange - this is the most common and costly mistake I see in DIY installations.
Having the right materials and tools on hand will save you countless trips to the hardware store and ensure professional results. Based on my experience with hundreds of bathtub installations, here's what you'll need:
Essential Tools:
Materials List:
Cost estimates range from $100-300 for materials, depending on your chosen solution and bathroom size. When selecting materials, I recommend consulting our guide to the best tub surrounds for proper installation to ensure compatibility with your overall bathroom design.
Learning from others' mistakes can save you time, money, and frustration. Here are the most common errors I've encountered in bathtub lip installations:
Never place backer board over the tub flange. This is the cardinal sin of bathtub installations. The flange is designed to sit behind the backer board, creating a waterproof barrier. Covering it traps water and creates a guaranteed failure point.
Don't ignore small gaps. Even 1/8 inch gaps can allow water infiltration. Always waterproof the space between backer board and tub flange, regardless of how small it seems.
Avoid abrupt transitions. When using different thickness materials, create gradual transitions rather than step-offs. Abrupt changes can cause tile cracking and create visible lines in your finished installation.
Don't skip the waterproofing membrane. Caulk alone is not sufficient for the gap between tub and backer board. Always use a proper waterproofing membrane for long-term protection.
Don't rush the measurements. Take measurements at multiple points and document everything. I've seen projects fail because measurements were only taken at one point and didn't account for variations along the tub length.
After working with professional tilers and plumbers, I've gathered these insider tips that can elevate your installation from good to great:
Test fit your backer board before securing it permanently. I recommend doing a dry fit with at least one sheet to identify any issues before you commit to the installation. This simple step can save hours of rework.
Use a laser level for reference lines when possible. While traditional levels work fine, a laser level makes it easier to maintain consistent lines across multiple walls, especially in larger bathrooms.
Consider the tile thickness in your calculations. Don't forget to account for the tile and thin-set mortar when determining your backer board placement. The finished tile surface should slightly overlap the tub flange for proper water shedding.
Plan your tile layout before installing backer board. Knowing your tile pattern and grout line locations can help you optimize backer board placement and minimize cuts.
When working with acrylic bathtub installation tips in mind, remember that acrylic tubs can flex slightly. Don't over-tighten mounting brackets, and consider using additional support underneath the tub base.
For complete bathroom renovations, understanding how different tub types affect installation is crucial. Our guide to the best alcove bathtubs provides insights into how different models handle flange placement and installation requirements.
No, never place cement board over a bathtub lip or flange. The flange is designed to sit behind the backer board, creating a waterproof barrier. Placing cement board over the flange traps water and creates a failure point that leads to water damage and mold growth.
The lip of a bathtub is called the flange or tile flange. It's a raised edge designed to sit behind the backer board and tile, creating a waterproof barrier that prevents water from getting behind the tub surround.
Leave a 1/8 to 3/16 inch gap between the bottom of the backer board and the tub flange. This small gap allows for proper waterproofing membrane application and prevents the backer board from sitting directly on the tub surface.
Yes, if your tub is accessible and plumbing allows, you can often slide the tub 1-2 inches to balance gaps between walls. Check drain and overflow connections first, and ensure proper support underneath the tub base before making adjustments.
RedGard and Kerdi Band are the most reliable waterproofing membranes for tub flange gaps. Apply over mesh tape reinforcement for added protection. For gaps over 1/4 inch, use backer rod first, then seal with silicone before applying the membrane.
Create gradual transitions using furring strips, specialty trim pieces, or tapered drywall beads. Avoid abrupt step-offs which can cause tile cracking and visible lines. Plan transitions during the backer board installation phase.
Solving a bathtub lip that sticks out might seem daunting, but with the right approach and attention to detail, it's entirely achievable for most DIY homeowners. The key is taking accurate measurements, choosing the appropriate solution for your specific situation, and never compromising on waterproofing.
I recommend starting with the simplest solution that addresses your measurement needs - often furring strips for smaller gaps or tub adjustment when possible. Only move to more complex solutions if necessary. Remember that proper preparation and waterproofing are more important than the specific solution method you choose.
Take your time with measurements, don't rush the waterproofing steps, and don't hesitate to consult professionals for complex situations. With these guidelines, you can achieve a professional-looking, watertight bathtub surround that will last for years to come.