A grout pen can be a handy, low-cost way to freshen up grout lines that have gone grey, yellowed, or patchy — but it works best as a cosmetic touch-up rather than a true repair. If your grout is cracked, crumbling, or harbouring deep mould, a grout pen won't solve the underlying problem. Here's what you need to know before you reach for one.
What Is a Grout Pen?
A grout pen (sometimes called a grout marker or grout paint pen) is essentially a paint-filled applicator designed to colour over existing grout lines. Most contain a water-based, opaque paint or epoxy-based coating that dries to a hard finish. They're widely available at Bunnings and Mitre 10 in a range of colours — white and off-white being the most popular for bathroom and kitchen tiles.
When a Grout Pen Works Well
Grout pens are genuinely useful in the right situations:
- Surface staining and discolouration — grout that has yellowed or greyed from age, cleaning products, or hard water deposits
- Lightly mouldy grout that has been properly cleaned and dried first
- Cosmetic refresh before selling a home or renting a property
- Small areas such as a splashback, vanity surround, or feature wall
- Grout that is structurally sound — no cracks, no missing sections, no movement
In these cases, a grout pen can make a tired bathroom or kitchen look noticeably cleaner with minimal effort and cost.
When a Grout Pen Won't Cut It
There are situations where a grout pen is the wrong tool for the job:
- Cracked or crumbling grout — paint over a crack and the crack is still there underneath
- Active mould growth — painting over mould traps moisture and the mould will return, often worse
- Wet areas with failing grout — in showers and around baths, compromised grout can allow water ingress behind tiles, leading to serious damage to the substrate and potential issues under the NZ Building Code clause E3 (Internal Moisture)
- Large floor areas — grout pens wear quickly underfoot and will need frequent reapplication
- Wrong colour match — if you can't match the original grout colour closely, the result can look patchy
How to Use a Grout Pen: Step by Step
If your grout is a good candidate for a pen, follow these steps for the best result:
1. Clean the grout thoroughly
Scrub grout lines with a stiff brush and a suitable grout cleaner. Remove all soap scum, mould, grease, and loose material. Rinse well and allow to dry completely — at least 24 hours in a well-ventilated space. In NZ's more humid regions (Northland, West Coast), allow longer drying time.
2. Test in a hidden spot
Apply the pen to a small, inconspicuous area first to check the colour match and adhesion before committing to the whole job.
3. Apply carefully
Run the pen steadily along each grout line. Most pens have a chisel or fine tip — use the edge for narrow lines. Work in small sections and wipe any overspill onto tiles immediately with a damp cloth before it dries.
4. Allow to cure
Follow the manufacturer's drying and curing times. Avoid wetting the surface for at least 24 hours.
5. Seal if recommended
Some grout pens include a sealing agent; others recommend applying a separate grout sealer once dry. A sealer will extend the life of the finish significantly.
How Long Does a Grout Pen Last?
This varies depending on the product, the surface, and how much wear and moisture the area receives. On a wall splashback with good ventilation, results can last a year or more. On a shower floor or heavily used kitchen floor, expect to reapply within a few months. It's a maintenance solution, not a permanent fix.
The Alternative: Regrout or Reclean
If your grout is in poor condition, the proper solution is to remove and replace the grout — a process called regrouting. This involves raking out the old grout with an oscillating tool or grout saw, cleaning the joints, and applying fresh grout. Products from Ardex and Mapei are well regarded in the NZ trade for quality grout systems.
For badly stained but structurally sound grout, a professional steam clean or chemical clean may restore the original colour without any painting at all — worth trying before reaching for a pen.
A Note on Wet Areas and the NZ Building Code
In wet areas (showers, baths, laundry tubs), grout is part of the waterproofing system. If grout is failing in these locations, it's important to address it properly. The MBIE Building Performance website has guidance on building code requirements for internal moisture (E3) and sanitary facilities (G13). Ongoing water ingress behind tiles can cause significant structural damage and may require a building consent for remediation work — check with your local council.
When to Call a Professional
Call a qualified tiler if:
- Grout is cracked, missing, or crumbling in a wet area
- You suspect water has gotten behind the tiles (hollow-sounding tiles, damp walls, lifting tiles)
- You want a lasting result on a large area
- You're unsure whether the substrate has been damaged
A licensed tiler will assess whether a regrout, retile, or waterproofing repair is needed. You can find experienced local tilers on tradedirectory.co.nz.
Site Safe
SiteWise
BCITO Qualified
