Removing old grout without scratching your tiles is absolutely doable as a DIY project — the key is choosing the right tools, working carefully, and taking your time. Rush the job or use the wrong equipment and you risk chipping glazed surfaces or gouging softer stone tiles, turning a straightforward regrout into an expensive repair.
Why You Might Need to Remove Grout
Grout deteriorates over time. It can crack, crumble, discolour, grow mould, or simply look tired. In wet areas like bathrooms and kitchens, failed grout can allow water to penetrate behind tiles — a serious issue under the NZ Building Code's E3 (Internal Moisture) requirements. Removing and replacing old grout restores the waterproof seal and freshens the look of your tiling without the cost of a full retile.
Tools You'll Need
Choosing the right tool is the single most important decision in this job.
- Oscillating multi-tool with a grout removal blade — the safest and most efficient option for most tiles. The blade vibrates rather than spinning, giving you much more control.
- Manual grout saw — a small hand tool with a carbide-tipped blade. Slower, but very precise and great for small areas or delicate tiles.
- Rotary tool (e.g. Dremel) with a grout bit — fast but harder to control; higher risk of scratching, especially on glazed or polished tiles.
- Angle grinder — generally not recommended for DIYers around tiles due to the high risk of damage.
You'll also need safety glasses, a dust mask (grout dust is a respiratory irritant — check WorkSafe NZ guidance on silica dust if working with natural stone), work gloves, a stiff brush, and a vacuum.
Step-by-Step: Removing Grout Safely
1. Assess Your Tiles First
Identify your tile type before you start. Glazed ceramic and porcelain tiles are relatively forgiving. Natural stone (marble, travertine, slate) and handmade or textured tiles scratch more easily and need extra care. If in doubt, test your chosen tool in a hidden corner first.
2. Set Up Your Work Area
Protect surrounding surfaces and ensure good ventilation. Grout removal creates a lot of fine dust. Dampen the grout lines lightly — this can help reduce airborne dust, though it won't eliminate it.
3. Work Along the Grout Line, Not Across It
Always run your tool along the centre of the grout joint, never at an angle across the tile face. Keep the blade or bit as vertical as possible. Apply light, steady pressure — let the tool do the work rather than forcing it.
4. Remove Grout in Passes
Don't try to remove all the grout in one pass. Make several shallow passes, gradually deepening the channel. You don't need to remove every last trace — aim to clear the top 2/3 of the grout depth to give new grout a solid key to bond to.
5. Clean Up Thoroughly
Vacuum out the joints, then use a stiff brush to remove loose debris. Wipe the tile faces with a damp cloth. Inspect each joint — any remaining loose or crumbling grout should be picked out with a grout saw or pointed tool.
Choosing New Grout
Once the joints are clean and dry, you're ready to regrout. Match your new grout type to the application:
| Grout Type | Best For | Notes |
|---|---|---|
| Cement-based (unsanded) | Joints under 3 mm | Most common, widely available |
| Cement-based (sanded) | Joints 3 mm and wider | Stronger for wider joints |
| Epoxy grout | Wet areas, high traffic | More durable, harder to apply |
For wet areas like showers, always use a waterproof or water-resistant grout and finish with a quality grout sealer once cured. Brands like Ardex and Mapei offer grout products widely available through NZ tile and trade suppliers. Sika also produces grout and tile adhesive products suited to NZ conditions.
You'll find a range of grout products and tools at Bunnings and Mitre 10.
Tips to Avoid Scratching
- Never use a metal scraper flat across the tile face — even brief contact can scratch glazed surfaces.
- Keep blades sharp — a dull blade requires more pressure and increases the risk of slipping.
- Go slowly around tile edges — the corners are most vulnerable to chipping.
- Test first — always do a test patch in an inconspicuous spot before committing to the whole area.
- For polished or natural stone tiles, consider consulting a professional tiler, as these materials are particularly unforgiving.
When to Call a Professional
Some situations are best left to a qualified tiler:
- Large areas — removing grout across an entire bathroom or kitchen floor is labour-intensive and the risk of cumulative damage increases with fatigue.
- Delicate or expensive tiles — marble, polished porcelain, handmade terracotta, or heritage tiles warrant professional care.
- Structural cracking — if grout is cracking because the tiles themselves are moving or the substrate is failing, regrout alone won't fix the problem. A tiler can diagnose the underlying cause.
- Shower recesses and wet areas — waterproofing in these areas is covered by the NZ Building Code. If you're concerned the waterproof membrane may have been compromised, get a professional assessment.
A skilled local tiler will have the right tools and experience to get the job done quickly and without damage. You can find qualified tilers in your area on tradedirectory.co.nz.
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