Choosing the right grout for your shower might seem straightforward, but get it wrong and you're looking at mould, leaks, and costly repairs down the track. New Zealand's humid bathroom conditions — especially in regions like Auckland and the West Coast — make grout selection even more important. This guide walks you through your options so you can make a confident, informed choice.
Why Grout Choice Matters in a Shower
Shower grout is constantly exposed to water, steam, soap scum, and temperature changes. Poor grout selection or application can lead to water ingress behind tiles, which is one of the most common causes of serious bathroom damage in NZ homes. Under the NZ Building Code, wet areas like showers must be waterproofed to comply with Clause E3 (Internal Moisture). The grout you choose plays a direct role in maintaining that waterproof barrier.
The Main Types of Shower Grout
Cement-Based Grout
Cement-based grout is the most widely used type and comes in two forms:
- Unsanded (non-sanded) grout — best for narrow joints (generally under 3 mm). Smooth texture, ideal for polished tiles and glass mosaic.
- Sanded grout — contains fine sand for added strength. Suited to wider joints (generally 3 mm and above). More resistant to shrinkage and cracking.
Cement grout is affordable and available in a huge range of colours from suppliers like Mapei and Ardex, both of which have strong product ranges stocked at NZ tile and trade stores. The downside: cement grout is porous and must be sealed after installation and periodically thereafter to resist moisture and staining in a shower environment.
Epoxy Grout
Epoxy grout is a two- or three-part system (resin, hardener, and sometimes filler) that cures to form a very hard, non-porous surface. It is:
- Highly water and stain resistant — no sealing required
- Resistant to mould and mildew
- More durable over the long term in wet areas
- Harder to work with — it sets quickly and requires careful, experienced application
- Generally more expensive than cement grout
For shower floors and walls that will see heavy daily use, epoxy grout is often the professional's preferred choice. Sika and Mapei both offer epoxy grout products suitable for wet areas.
Premixed (Acrylic) Grout
Premixed grouts are convenient but are not recommended for showers. They don't cure as hard as cement or epoxy grout and can remain slightly flexible and porous — a poor combination for a constantly wet environment. Avoid these in any wet area application.
Comparing Your Options
| Grout Type | Best For | Sealing Required | Difficulty | Cost (Guide Only) |
|---|---|---|---|---|
| Unsanded cement | Joints under 3 mm | Yes | Easy–Moderate | Low |
| Sanded cement | Joints 3 mm+ | Yes | Easy–Moderate | Low |
| Epoxy | All shower joints | No | Moderate–Hard | Medium–High |
| Premixed acrylic | Dry areas only | — | Easy | Low |
Cost is a general guide only and will vary by brand, retailer, and quantity.
Choosing the Right Colour
Colour choice is partly aesthetic, but there's a practical side too. Lighter grout colours show soap scum and mineral deposits more readily, while darker grout can fade over time if not properly sealed. Mid-tone greys and warm neutrals tend to be a popular, practical choice in NZ showers. Always check the grout manufacturer's colour chart in natural light before committing — colours can look very different once dry.
Joint Width and Tile Type
The width of your tile joints (the gaps between tiles) determines whether you need sanded or unsanded grout. Your tile supplier or tiler can advise on the correct joint width for your specific tile — rectified tiles (precision-cut) typically use very fine joints, while natural stone or handmade tiles may need wider joints. Using the wrong grout type for your joint width can cause cracking or poor adhesion.
Sealing Cement Grout in a Shower
If you go with cement-based grout, sealing is non-negotiable in a shower. Allow the grout to cure fully (check the manufacturer's instructions — typically at least 48–72 hours), then apply a quality penetrating grout sealer. You'll need to reseal periodically — how often depends on usage and the product used, but checking annually is a good habit. BRANZ provides useful guidance on wet area maintenance for NZ homes.
Silicone Sealant: Don't Forget the Corners
Grout should never be used in internal corners or the junction between the shower wall and floor. These movement joints must be filled with flexible silicone sealant to allow for the natural movement of the building. Using grout in these spots will almost always result in cracking. Use a sanitary-grade silicone that matches your grout colour for a neat finish.
When to Call a Professional
Tiling a shower — particularly waterproofing the substrate before tiles go on — is skilled work. While grouting itself is not legally restricted work in NZ, the waterproofing membrane installation underneath is critical and must comply with NZ Building Code Clause E3. If the membrane is done incorrectly, no amount of good grouting will save you from water damage.
If you're retiling a shower from scratch, or if you're unsure about the condition of the existing waterproofing, it's strongly advisable to engage a qualified tiler. A good tiler will also ensure correct substrate preparation, tile layout, and grout selection for your specific situation. You can find licensed local tilers on tradedirectory.co.nz.
Note: Any plumbing work in the shower (moving or installing waste drains, shower mixers, etc.) is restricted work under NZ law and must be carried out by a registered plumber or drainlayer. Check the Plumbers, Gasfitters and Drainlayers Board to verify a tradesperson's registration.