The Most Expensive Part of a Bathroom Renovation (And How to Save Thousands on Yours)

Bathroom renovations are one of the most rewarding upgrades you can make to your home — they add comfort, improve functionality, and significantly boost resale value. But they’re also one of the most complex and expensive renovation projects homeowners take on. And while most people assume luxury tile or high-end fixtures drive the cost, the reality is that what’s underneath the surface often has the biggest impact on your budget.

In this guide, we’ll break down the key factors that make bathroom remodels costly, reveal the part of the project that tends to eat up the largest chunk of your budget, and share how Luma Build Design has helped homeowners across Centre Wellington, Guelph, Elora, Fergus, and beyond save thousands — without compromising quality, design, or long-term value.

Why Bathroom Renovations Are One of the Most Expensive Projects in Your Home

Bathroom renovations might be one of the smallest spaces in a home, but they often have the highest cost per square foot of any room remodel. The reason is simple: bathrooms require nearly every type of trade and material in a condensed space — plumbing, waterproofing, electrical, framing, insulation, tiling, and finish work all have to work together perfectly. This means the cost isn’t just about what you see on the surface, but also the technical work happening behind the walls and under the floors.

One of the biggest misconceptions homeowners have is that expensive tile or designer vanities are what push bathroom remodel budgets up. While premium materials do affect pricing, they’re rarely the most expensive part. The real cost drivers come from the critical systems that ensure your bathroom functions properly and lasts for decades — things like waterproofing, plumbing, and ventilation. If these foundational elements aren’t done right, you risk water damage, mold growth, and costly repairs down the road.

At Luma Build Design, we’ve seen countless projects across Elora, Fergus, and Guelph where a previous renovation looked beautiful on the outside but was failing internally. That’s why we prioritize quality installation over flashy finishes. Investing properly in the foundation of your bathroom isn’t just about safety — it’s about saving thousands in potential future repairs and protecting your home’s overall value.

Another factor that adds complexity (and cost) is the small footprint. Bathrooms pack a lot of functionality into a limited space, so every decision — from plumbing reroutes to fixture placement — can affect labor time and material use. A small misstep early on can lead to significant changes in scope later, which is why detailed planning and expert project management are essential.

Finally, local building codes and permit requirements in regions like Centre Wellington, Guelph-Eramosa, and Woolwich add another layer of technical precision. Bathrooms are considered “wet zones,” meaning there’s less margin for error and more oversight, which further increases labor complexity and inspection requirements.

The Most Expensive Part of a Bathroom Renovation: Waterproofing & Plumbing

While it’s easy to get caught up in design decisions like tile patterns or faucet styles, the true cost champion in nearly every bathroom remodel is the waterproofing and plumbing system. These are the backbone of the entire project — and also the most labor-intensive, regulated, and risk-prone elements of a bathroom build.

Waterproofing is where everything begins. If your shower, tub surround, or flooring isn’t sealed properly, water will find its way into the walls and subfloor — leading to rot, mold, and structural issues. That’s why we rely on professional-grade systems like Schluter®-KERDI Board, which offer a lightweight, waterproof substrate that creates a completely sealed envelope behind your tile. When combined with a high-performance sealant like GE Advanced Silicone 2 or Loctite® Polyseamseal Tub & Tile, you get a waterproofing solution that protects your bathroom for decades.

Plumbing is another cost-heavy aspect because it often involves more than just swapping out fixtures. Relocating a shower drain, installing a new tub, or adding body sprays requires reworking supply lines, drain slopes, and venting systems. Each of these tasks must meet strict plumbing codes and often requires licensed trades — which adds to labor costs. The upside? When done right, plumbing upgrades significantly improve water efficiency, increase resale value, and provide a better user experience.

We’ve helped many homeowners across Kitchener, Elmira, and Waterloo save thousands on this part of the project by optimizing layouts. For example, instead of relocating the toilet or shower, we sometimes redesign the space around existing plumbing — a small change that can reduce costs dramatically while still achieving a modern, functional design.

Beyond materials and layout, waterproofing and plumbing costs are also influenced by the condition of your existing bathroom. Older homes — especially those in areas like Arthur, Elora, Fergus or Guelph’s historic districts — often have outdated or non-compliant systems that require more extensive updates. While this adds upfront expense, it’s an investment that ensures long-term durability and prevents costly future failures.

Top 5 Factors That Influence Bathroom Renovation Cost (Without Talking Dollars)

Even without listing exact prices, we can confidently say that five key factors almost always determine the final cost of a bathroom remodel. Understanding these elements will help you make smarter decisions and prioritize your budget effectively:

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1. Plumbing Layout Changes

Moving major fixtures like toilets, tubs, or showers requires rerouting plumbing — often through concrete or joists — which significantly increases labor time. Whenever possible, keeping fixtures in the same location can help control costs.

2. Waterproofing System Quality

Choosing high-quality waterproofing products like Schluter®-KERDI or Nuco Newflex ensures long-term performance and avoids costly water damage later. Cheap alternatives may save a little upfront but can lead to major repair costs down the road.

3. Fixture Selection & Brand Quality

The fixtures you choose — from Kohler bathtubs to Moen shower valves and Delta faucets — dramatically affect both upfront cost and long-term durability. Higher-end options typically offer better warranties, water efficiency, and resale appeal.

4. Tile & Finish Complexity

Labor costs increase with intricate tile layouts, custom niches, or premium materials. Simple layouts can deliver a high-end look without excessive labor time, helping balance cost and style.

5. Existing Conditions & Demolition Needs

Hidden issues like rotted subfloors, old cast-iron pipes, or asbestos tile can increase scope quickly. A thorough pre-renovation inspection helps identify these surprises early, allowing for more accurate project planning.

DIY vs. Professional Bathroom Renovations – What’s Really Worth It?

One of the most common questions homeowners have is whether they should tackle parts of a bathroom renovation themselves to save money. The truth is, some parts of a bathroom remodel are DIY-friendly — but the most critical, expensive components are usually best left to professionals.

Where DIY can make sense:If you’re comfortable with tools and have renovation experience, certain cosmetic tasks like painting, installing accessories, or even replacing a vanity can be done yourself. These jobs typically don’t involve plumbing, waterproofing, or structural changes, so the risk of expensive mistakes is relatively low. DIYing these smaller tasks can save a few hundred dollars — but the savings are often minimal compared to the total cost of a full renovation.

Where hiring a professional is essential: Plumbing, waterproofing, electrical work, and tile installation are areas where even small mistakes can lead to massive problems. A poorly installed shower membrane or improperly sealed joint can cause hidden water damage, mold, and structural issues that cost thousands to fix later. Using high-quality materials like Schluter®-KERDI Board and GE Advanced Silicone 2 is only effective when installed correctly — and that level of precision comes from experience.

At Luma Build Design, we’ve been called in countless times to fix DIY bathroom projects that went wrong — often costing homeowners far more than if they had hired us from the beginning. Across Guelph, Fergus, and Elmira, we’ve helped clients correct moisture issues, fix failing tile installations, and bring plumbing up to code — all problems that could have been avoided with proper professional installation.

Ultimately, if your bathroom renovation involves plumbing, waterproofing, or layout changes, hiring a professional is an investment that pays off in long-term durability, safety, and peace of mind. Save the DIY work for finishing touches — and let experts handle the critical systems that protect your home.

Frequently Asked Questions About Bathroom Renovation Costs

Q1: What’s usually the most expensive part of a bathroom renovation?

A: Waterproofing and plumbing almost always represent the largest share of a bathroom remodel budget. These systems require specialized materials, precise installation, and compliance with building codes — all of which add to labor and material costs.

Q2: Can I save money by using cheaper materials?

A: While you can reduce upfront costs with budget materials, it often leads to expensive repairs later. Investing in high-quality products like Schluter®-KERDI, Nuco Newflex, and Moen fixtures ensures durability, performance, and better long-term value.

Q3: How long does a bathroom renovation usually take?

A: A standard bathroom remodel typically takes 2–4 weeks, depending on the complexity, layout changes, and any unforeseen issues. Older homes or projects requiring significant plumbing updates may take slightly longer.

Q4: Do I need a permit for a bathroom renovation?

A: In most townships — including Centre Wellington, Woolwich, and Guelph-Eramosa — you’ll need a permit if your renovation involves plumbing, structural changes, or electrical work. Your contractor will typically handle the permit process for you.

Ready to Transform Your Bathroom?

A bathroom renovation is one of the smartest investments you can make in your home — but it’s also one of the most complex. Understanding where the major costs come from and how to make smart material and layout decisions will help you maximize value and avoid costly mistakes.

At Luma Build Design, we’ve helped homeowners across Elora, Fergus, Kitchener, Guelph, and beyond design and build bathrooms that are not only beautiful but also durable, efficient, and built to last. Whether you’re dreaming of a modern walk-in shower, a spa-like retreat, or a complete bathroom overhaul, our team is here to help.

👉 Contact our team today to schedule a consultation or explore our Bathroom Renovation Services. You can also view past renovation projects to see how we’ve helped homeowners create spaces they love — all while staying on budget.

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• How Much Does a Basement Renovation Cost in 2025?

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