022 6935871Building from Scratch? 7 Bathroom Features to Plan Before the Slab Is Poured
When designing a new home or planning a full-scale renovation, most people focus on visual finishes. However, what sits behind the walls and beneath the floor often matters more in the long run. The early stages of a build, especially those before the slab is poured, shape how functional a bathroom will be years after the house is complete.
Several decisions must happen during this phase, including plumbing placement, drainage direction, structural support for fixtures, and wiring paths. These components form the framework of every bathroom and cannot be adjusted easily once concrete is set or walls are closed. While it might seem tempting to delay decisions until the design is more developed, doing so can result in complications, delays, or expensive retrofitting.
This article focuses on helping homeowners, designers, and renovators understand which elements need attention before the slab goes in. With thoughtful planning, you can avoid problems later and build bathrooms that feel considered and complete from the start.
1. Plumbing Placement: Getting It Right from the Ground Up
Toilet Positioning and Floor Waste Planning
One of the first steps is identifying exactly where the toilet and floor waste will be located. These elements require fixed pipework beneath the slab. If their locations change after pouring, builders may need to jackhammer through concrete to relocate them — a disruptive and expensive process.
Shower Drainage and Waterproofing Alignment
Where the shower will be located also matters early. You’ll want to place the drain in a spot that aligns with the desired layout while maintaining an adequate slope for water flow. Pre-slab coordination ensures the shower tray or tiled floor will align with waterproofing zones and drainage points without awkward adjustments.
Early Coordination with the Plumber
Planning doesn’t sit solely with the homeowner or designer. It’s essential to involve a licensed plumber who understands the specific requirements of your build. Working together, you can finalise drainage points before the slab boxing begins. Doing this step early allows for the smooth placement of pipes and avoids any last-minute surprises.
Can’t I finalise these details after framing starts?
In most cases, no. Once the concrete slab is in place, changing plumbing locations requires significant rework. That’s why it’s important to lock in these decisions before the concrete pour.
2. Drainage Angles and Waste Fall Requirements
Understanding Required Slopes
For water to drain properly, waste pipes must have a slight and consistent slope. This is often called the “fall,” and it ensures gravity carries waste away from the bathroom effectively. If the slope is too steep, water can move too quickly and leave solids behind. If it’s too flat, water may pool or back up.
Setting Falls for Each Fixture
Different bathroom fixtures require different fall gradients. A walk-in shower needs a steeper fall than a bath waste. Similarly, floor wastes must align with the floor gradient to prevent water from pooling in low spots. Planning these angles requires precision and should comply with New Zealand’s plumbing code.
Avoiding Mistakes Through Early Planning
Failing to consider fall angles can lead to functional issues. Water that doesn’t drain properly may pool, seep into other areas, or damage tiles. These problems often surface long after construction ends, making early planning essential.
3. Window Placement for Natural Light and Ventilation
Placement and Privacy Considerations
Natural light helps make bathrooms feel larger and more inviting, but placement matters. Too low, and windows compromise privacy. Too high, and ventilation becomes less effective. Consider the balance between light, airflow, and privacy when planning window positions.
Types of Windows That Work Well
Frosted glass helps retain privacy without reducing light. Louvre or awning windows allow for ventilation even during light rain. These styles suit most Kerikeri homes and fit easily into standard framing sizes when specified early.
Framing and Reveal Requirements
Bathroom windows often need custom reveals or lintels to support their placement. Including these in early specifications ensures your window supplier and builder are aligned. Making adjustments later could disrupt the waterproofing plan or clash with internal fixtures.
4. In-wall framing for Future Fittings and Fixings
Wall Supports for Mounted Features
Floating vanities, wall-hung toilets, and large mirrors all need firm support inside the wall. Standard timber framing may not be enough, especially for heavier features. If not considered early, fixing these later may require cutting into finished walls.
Future-Proofing for Accessibility
Even if you don’t need accessible fittings now, it’s smart to include support for grab rails and reinforced fixtures. Adding these supports in the early phase costs little and avoids future inconvenience.
Structural Adjustments for Heavier Items
Sometimes, steel framing or extra timber nogs are required. Shower screens, especially frameless ones, need solid fixing points. These details must be planned during wall framing, not after.
What if I change my mind about fittings later?
You can still change surface items like tapware or mirrors. However, the support structure for things like towel rails or vanities needs to be in place before the walls are closed. Otherwise, changes might involve wall repairs or compromise the installation.
5. Recessed Shower Niches and Storage Planning
Framing in Recessed Storage Early
Recessed niches for shampoo bottles or in-wall shaving cabinets must be framed during construction. If planned too late, they may interfere with plumbing or require moving structural elements.
Avoiding Conflicts with Plumbing Lines
Check for any water lines or vent pipes in the same wall before locking in your storage features. Planning these together helps you avoid clashing systems and keeps everything functional and neat.
6. Pre-wiring for Lighting and Heated Towel Rails
Planning for Light Fixtures and Mirror Wiring
Backlit mirrors and LED strip lights have grown in popularity. These require power points or low-voltage wiring to be placed in specific spots. Running conduits during wall framing avoids the need to chase wires through finished walls later.
Heated Towel Rails and Smart Switches
These elements need more than just power — they may need timers or smart switches mounted at accessible heights. Knowing where switches or controllers will go ensures compliance with electrical safety zones and clearances in wet areas.
Avoiding Exposed Conduits or Retrofitting
Planning power needs to avoid messy or exposed conduits later. Retrofits often look unplanned or require patching over tiled areas. A clear plan for electrical features improves both functionality and appearance.
7. Shower and Bath Positioning for Layout and Flow
Clear Paths and Entry Directions
Think about how people will enter and move through the space. Avoid placing the shower door in a spot that clashes with a vanity or opens into the walkway. Consider where water might splash and how traffic flows in and out.
Sightlines from Entry Points
Position toilets where they’re not directly visible when entering the room. Likewise, avoid placing baths where they create pinch points in smaller bathrooms. These small layout details affect how the room feels and functions every day.
Supporting Screens and Bath Edges
Walls that support shower screens or bath edges need extra bracing. If not specified early, tilers and installers may need to adjust their work, leading to inconsistent finishes or delays.
Is this advice only for new homes?
No. While much of this applies to new builds, any bathroom renovation that involves moving plumbing or walls should follow the same early-stage planning principles.
Why Your Bathroom Layout Matters More Than the Tiles
While it’s easy to focus on tapware or tile colour, those elements are changeable. A poorly thought-out layout, on the other hand, is harder to fix and often more disruptive. Functional issues such as tight corners, poorly placed doors, or inaccessible storage are problems people only notice once the bathroom is in daily use.
Instead of rushing into finishes, take the time to evaluate movement, clearance, sightlines, and user comfort. These choices shape how the bathroom works, not just how it looks.
Conclusion
Planning a bathroom during the early stages of a build requires more than choosing finishes or browsing inspiration photos. Before the slab is poured, key decisions need to be made about plumbing placement, drainage angles, electrical wiring, and structural supports. These steps set the foundation for how the bathroom will work in daily life, not just how it will appear.
Whether you’re building new or undertaking a major home renovation in Kerikeri, this level of foresight reduces the chance of layout mistakes, costly changes, or functionality issues later. Being proactive in the early stages gives you more control over the outcome and ensures the bathroom suits your needs for years to come.
What do I ask builders when getting house renovation quotes?
Ask whether pre-slab planning is included in the quote. Check how flexible the layout is once the slab is down and whether a plumber or designer is consulted early in the process. These questions help ensure your project stays on track from the start.
