Matching new grout to old grout is one of the trickier DIY tiling jobs — but with the right preparation and a bit of patience, you can get a result that blends in well. The key is understanding that old grout rarely looks like it did when it was first laid, so your starting point is always getting the existing grout as clean as possible before you try to match it.
Why Grout Colour Matching Is Challenging
Grout changes colour over time due to dirt, mould, mineral deposits, cleaning products, and general wear. What was once a bright white or a clean mid-grey can shift significantly. New grout also looks different when wet versus dry, and it continues to lighten slightly as it cures. These variables mean an exact match is rarely guaranteed — but a close match is very achievable.
Step 1 — Deep Clean the Existing Grout First
Before you even think about choosing a colour, thoroughly clean your existing grout. Surface grime can make grout appear several shades darker than its true colour. Use a dedicated grout cleaner or a paste of baking soda and water, scrubbing with a stiff grout brush. For stubborn mould or staining — common in NZ bathrooms due to our humid climate — a diluted bleach solution can help on light-coloured grout (test in a hidden spot first).
Once clean, allow the grout to dry completely — ideally 24 hours — before assessing the colour. Natural light gives the most accurate reading.
Step 2 — Identify Your Existing Grout Type and Colour
There are two main grout types you'll encounter:
- Cement-based grout — the most common in NZ homes, available in sanded (for joints wider than about 3 mm) and unsanded varieties.
- Epoxy grout — harder, more stain-resistant, and typically used in commercial settings or wet areas. It has a slightly different sheen.
If you know the original brand and colour name (check old receipts or photos from the build), that's your best starting point. Common NZ suppliers include Ardex and Mapei, both of which have wide colour ranges and are stocked at trade and hardware stores.
Step 3 — Use a Grout Colour Chart In-Store
Take a tile sample or a clear photo of your cleaned, dry grout to your local tile shop, Bunnings, Mitre 10, or PlaceMakers. Hold physical grout colour chips directly against your sample in natural light — don't rely on screen colours or catalogue images alone.
Ask staff if they have a grout colour selector tool, which some suppliers provide. Mapei and Ardex both offer colour-matching resources.
Tips for Choosing the Right Shade
- Go slightly lighter than you think you need — new grout dries lighter than it looks when mixed.
- If the existing grout has yellowed or warmed with age, look for a colour with a warm undertone rather than a cool grey or stark white.
- Buy a small quantity first and do a test patch in an inconspicuous area. Allow it to cure fully (usually 24–72 hours) before judging the colour.
Step 4 — Mix and Apply Carefully
Follow the manufacturer's mixing instructions precisely. Consistency in water ratio is important — too much water weakens the grout and can affect the final colour. Mix only what you can use within the pot life (usually 30–60 minutes for cement grout).
Apply new grout to a small test area, clean off the haze, and let it cure before comparing to the surrounding grout in natural light.
Step 5 — Consider a Grout Colourant as an Alternative
If you can't get a close enough match with new grout, a grout colourant or grout paint can be applied over existing clean grout to change or refresh its colour. These products are available at hardware stores and can be a good option when you want to unify the look of an entire tiled surface rather than just patching. They do require thorough surface preparation and may need reapplication over time.
Realistic Expectations
Be honest with yourself: a perfect invisible match is difficult, especially on older tiles where the grout has aged significantly. In many cases, a close match that isn't noticeable from a normal viewing distance is the realistic goal. If the area is prominent — like a kitchen splashback or main bathroom — it may be worth regrout the entire surface for a uniform result.
For areas subject to moisture, make sure any new grout in wet zones complies with the requirements of relevant NZ Standards for wet area construction (check with your tile supplier or BRANZ for the applicable standard) and the NZ Building Code clause E3 (Internal Moisture). BRANZ has useful guidance on wet area construction and maintenance.
When to Call a Professional
If the grout failure is widespread, if tiles are cracked or lifting, or if you suspect a waterproofing issue behind the tiles (especially in showers or around baths), it's time to call a qualified tiler. Waterproofing in wet areas is critical under the NZ Building Code, and getting it wrong can lead to costly structural damage. A licensed tiler will also have access to professional-grade colour-matching tools and a broader range of grout products.
You can find experienced local tilers on tradedirectory.co.nz — always check they have relevant experience with your tile type and wet area work.
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