Applying silicone sealant neatly in shower corners is one of those jobs that looks simple but catches plenty of DIYers out. With the right preparation, a quality sanitary silicone, and a bit of patience, you can achieve a clean, watertight finish that will last for years and keep moisture out of your wall cavities.
Why Shower Corner Sealing Matters
Shower corners are a primary weak point for water ingress. Grout alone is not flexible enough to cope with the slight movement that occurs between walls and the shower base or between two tiled walls — it will crack over time. Silicone sealant is flexible, waterproof, and mould-resistant, making it the correct material for these joints. Under the NZ Building Code (particularly clauses E3 — Internal Moisture — and E2 — External Moisture), wet areas must be properly waterproofed, and failed sealant joints are a common cause of hidden water damage. You can read more about wet-area requirements at MBIE Building Performance.
Tools and Materials You'll Need
- Sanitary silicone sealant (mould-resistant, suitable for wet areas)
- Silicone gun (a smooth-rod gun gives better control than a ratchet gun)
- Masking tape (low-tack painter's tape works well)
- Stanley knife or silicone removal tool
- Methylated spirits or isopropyl alcohol
- Clean cloths or paper towels
- A small bowl of water and a few drops of dish soap
- A silicone finishing tool or your finger
Choosing the Right Silicone
Always use a sanitary or bathroom-grade silicone that is labelled mould-resistant. Standard clear or white silicone is available from Bunnings and Mitre 10. Match the colour to your grout where possible — most brands offer white, off-white, grey, and sometimes colour-matched options. Brands such as Sika offer sanitary silicone products; check Sika NZ for their wet-area range. Avoid using general-purpose silicone in showers — it won't resist mould or the constant wet-dry cycles.
Step 1 — Remove the Old Sealant Completely
If you're resealing, all of the old silicone must come out. Use a Stanley knife or a dedicated silicone removal tool to cut and peel away the old bead. Any silicone left behind will prevent the new sealant from bonding properly. Take your time — this is the most important step.
Step 2 — Clean and Dry the Surface Thoroughly
Wipe the joint with methylated spirits or isopropyl alcohol on a clean cloth to remove soap scum, grease, and any silicone residue. Allow the surface to dry completely — ideally leave the shower unused for at least 24 hours before resealing. Silicone will not bond to a damp surface, so this step cannot be rushed.
Step 3 — Apply Masking Tape
This is the secret to a professional-looking finish. Apply two strips of low-tack masking tape along each side of the joint, leaving a gap of 4–6 mm (or the width of your intended bead). Press the tape edges down firmly so silicone can't bleed underneath. Straight tape lines mean a straight, neat bead.
Step 4 — Cut the Nozzle and Load the Gun
Cut the nozzle at a 45-degree angle, making the opening about 4–5 mm wide. Smaller is better — you can always do a second pass, but too much silicone is hard to control. Load the cartridge into your silicone gun and do a small test bead on a piece of cardboard to get a feel for the flow.
Step 5 — Apply the Silicone Bead
Hold the gun at roughly 45 degrees to the corner. Move steadily and consistently along the joint in one smooth pass, applying even pressure. Try to complete each corner in a single continuous run rather than stopping and starting, which creates lumps. Work from top to bottom on vertical joints.
Step 6 — Tool the Bead Smooth
Dip your finger or a silicone finishing tool in the soapy water — this stops the silicone sticking to you. Run it firmly along the bead in one smooth stroke, pressing the silicone into the joint and creating a slightly concave profile. Do this immediately after applying the bead, before it starts to skin over (most silicones begin skinning within 5–10 minutes).
Step 7 — Remove the Masking Tape
Peel the masking tape away straight away, before the silicone skins. Pull it back at a low angle, away from the bead. If you wait too long, the tape will tear the edges of your bead. Once the tape is off, you'll have clean, sharp edges.
Step 8 — Allow Full Cure Time
Most sanitary silicones are touch-dry within an hour but need 24–48 hours to fully cure before the shower is used. Check the manufacturer's instructions on the cartridge. Avoid getting the joint wet during this period.
| Step | Key Point |
|---|---|
| Remove old silicone | Must be 100% gone for new silicone to bond |
| Clean & dry | Methylated spirits; surface must be bone dry |
| Masking tape | 4–6 mm gap; press edges firmly |
| Cut nozzle | 45° angle, 4–5 mm opening |
| Apply bead | One smooth, steady pass |
| Tool smooth | Soapy finger or tool, immediately |
| Remove tape | Straight away, before skinning |
| Cure | 24–48 hours before use |
When to Call a Professional
If you notice cracked tiles, soft or hollow-sounding substrate, or signs of water damage behind the wall (staining, mould, or soft GIB board), stop and call a licensed tiler or builder. What looks like a simple reseal job may indicate a failed waterproofing membrane underneath — a much bigger issue that requires professional repair to meet the NZ Building Code. You can find qualified local tilers on tradedirectory.co.nz. For any concerns about waterproofing compliance, BRANZ publishes good guidance on wet-area construction.
Safety note: Work in a well-ventilated space when using silicone solvents and sealants. Check WorkSafe NZ for safe handling of chemical products.
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