Installing a floating floor in a room with a floor drain is absolutely doable, but it requires more planning than a standard installation. The key challenges are maintaining drainage access, managing moisture, ensuring the floor still drains effectively, and keeping your installation compliant with the NZ Building Code — particularly clauses E3 (internal moisture) and G13 (foul water drainage).
Understand the Room Type First
Before you buy a single plank, identify what kind of room you're working in. Floor drains are most common in:
- Laundries – moderate moisture exposure
- Bathrooms and wet areas – high moisture, strict waterproofing requirements
- Garages or utility rooms – lower moisture but often uneven concrete substrates
Wet areas (showers, bathrooms) have specific waterproofing requirements under NZ Building Code clause E3 and are generally not suitable for standard floating floors. If your drain is inside a shower or wet zone, a floating floor is almost certainly the wrong product — tile or sheet vinyl over a properly waterproofed substrate is the appropriate solution. Always confirm with your local council or a Licensed Building Practitioner if you're unsure.
For laundries and utility rooms where the drain is a safety overflow rather than a primary drainage point, a floating floor can work well with the right product and method.
Choose the Right Floating Floor Product
Not all floating floors are created equal when moisture is involved. Your best options for rooms with drains are:
| Product Type | Water Resistance | Suitable for Drain Rooms? |
|---|---|---|
| Luxury Vinyl Plank (LVP) / SPC | Excellent | Yes (best choice) |
| Laminate (standard) | Poor | No |
| Water-resistant laminate | Moderate | Marginal — laundry only |
| Engineered timber | Moderate | Laundry only, with care |
Rigid-core Luxury Vinyl Plank (LVP) or Stone Plastic Composite (SPC) flooring is the top recommendation. These products are 100% waterproof at the plank level, dimensionally stable, and widely available at Bunnings and Mitre 10. Always check the manufacturer's specifications for wet area suitability before purchasing.
Prepare the Subfloor Thoroughly
A floating floor must sit on a flat, clean, and dry subfloor. In rooms with drains, the subfloor often slopes slightly toward the drain — this is intentional and important.
- Check the slope: A gentle fall toward the drain (typically 1:100 or as specified) is fine and should be maintained. Floating floors can tolerate minor slopes, but check your product's tolerance (usually no more than 3 mm over 1.8 m).
- Level high spots: Use a floor-levelling compound such as products from Ardex or Mapei to flatten any humps. Do not fill the drain fall.
- Moisture test: Concrete subfloors must be tested for moisture vapour transmission. Use a calcium chloride test or a moisture meter. High readings mean you need a vapour barrier or moisture-tolerant underlayment.
- Clean thoroughly: Remove all dust, adhesive residue, and debris.
Plan the Drain Opening Carefully
This is the most critical step. The floor drain must remain fully accessible and functional — blocking or restricting a floor drain can breach the NZ Building Code and create serious drainage problems.
Steps for cutting around the drain:
- Lay out your planks dry (without clicking them together) to plan the layout and minimise cuts around the drain.
- Mark the drain position on the planks that will surround it.
- Cut planks to fit around the drain grate, leaving a small gap (typically 5–10 mm) between the plank edge and the drain body. This gap allows water to reach the drain.
- Do not cover the drain grate — the grate must remain removable for cleaning and maintenance. Many installers use a drain trim ring or tile insert grate that sits flush with the finished floor height.
- Seal the cut edges of LVP or laminate planks around the drain with a waterproof sealant such as a product from Sika to prevent moisture wicking into the core.
- Check the drain grate height — you may need to raise or replace the grate to sit flush with your new floor surface. This is important for both aesthetics and trip hazard prevention.
Expansion Gaps and Perimeter Sealing
Floating floors expand and contract with temperature and humidity changes. Always leave the manufacturer's recommended expansion gap around all fixed objects — walls, cabinetry, pipes, and the drain body itself. Typically this is 8–12 mm at walls and 5–10 mm around penetrations.
Cover wall expansion gaps with skirting boards or scotia. Around the drain, the gap can be left open (to allow drainage) or fitted with a flexible sealant bead — check your product's installation guide for guidance.
Underlayment Considerations
In rooms with drains, choose an underlayment with a built-in vapour barrier (look for products with a polyethylene film backing). Do not run underlayment over the drain opening — cut it back neatly so the drain remains unobstructed. Some SPC/LVP products have underlayment pre-attached; confirm this is appropriate for your moisture conditions.
Do You Need a Building Consent?
In most cases, replacing or installing a floating floor is exempt from building consent under Schedule 1 of the Building Act 2004. However, if you are altering the drainage system itself (repositioning a drain, changing pipe connections), that work may require consent and must be carried out by a registered drainlayer licensed through the Plumbers, Gasfitters and Drainlayers Board. Always confirm with your local council before starting.
When to Call a Professional
Call a qualified flooring installer or tradesperson if:
- The room is a wet area (shower, bathroom) — waterproofing and tiling is almost always the right solution
- The subfloor has significant moisture issues or structural damage
- You need to alter or raise the drain to suit the new floor height — this is restricted plumbing/drainlaying work
- You're unsure about Building Code compliance for your specific situation
You can find experienced local flooring installers and plumbers on tradedirectory.co.nz.
