A leaking gutter joint is one of the most common — and most fixable — home maintenance issues in New Zealand. In most cases, you can reseal a joint yourself in under an hour using a tube of appropriate sealant, basic tools, and a safe ladder. Here's how to do it properly so the repair actually lasts.
Safety First: Working at Height
Before you climb anything, take a moment to think about ladder safety. Falls from ladders are a leading cause of serious injury in NZ homes. Always use a rated, stable ladder on firm, level ground, have a second person to foot the ladder, and never overreach — move the ladder instead. If your gutters are above a single storey or over a difficult surface, seriously consider hiring a professional. WorkSafe NZ has useful guidance on working safely at height.
What You'll Need
- Gutter sealant or silicone (see product notes below)
- Stiff brush or old paintbrush
- Putty knife or flat scraper
- Clean rags or paper towels
- Methylated spirits or a dedicated cleaner/degreaser
- Caulking gun
- Gloves and safety glasses
- Stable ladder
Choosing the Right Sealant
Not all silicone is equal for gutters. Standard bathroom silicone is not recommended — it isn't designed for the UV exposure, temperature swings, and constant water contact that gutters experience in NZ's varied climate.
Look for a product specifically labelled for gutters or roofing, such as:
- Gutter and roof sealants (available at Bunnings or Mitre 10)
- Polyurethane-based sealants — these are often more flexible and durable than standard silicone for metal gutters
- Sika produces a range of construction sealants suitable for this application
Check the product label to confirm it's compatible with your gutter material — uPVC (plastic), aluminium, steel, or copper all have slightly different requirements. When in doubt, ask at the trade counter.
Step-by-Step: Sealing the Joint
Step 1 — Clear the Gutter
Remove all leaves, debris, and standing water from the gutter around the leaking joint. You can't seal a wet, dirty surface effectively. Flush the area with a hose and let it dry completely — this may mean waiting for a dry day.
Step 2 — Remove Old Sealant
Use a putty knife or scraper to carefully remove as much of the old, failed sealant as possible. Be gentle with plastic gutters to avoid cracking them. Getting back to a clean surface is the most important step — new sealant won't bond well over old, peeling material.
Step 3 — Clean and Degrease
Wipe the joint area thoroughly with methylated spirits or a suitable degreaser on a clean rag. Allow it to dry fully. Any grease, algae, or residue will prevent proper adhesion.
Step 4 — Apply the Sealant
Load your caulking gun and cut the nozzle at a slight angle to match the width of the joint. Apply a continuous, even bead of sealant along the full length of the joint, pressing it into any gaps. Work from one end to the other without stopping if possible.
Smooth the bead with a wet finger or a caulking tool to ensure good contact with both surfaces. Remove any excess with a damp rag before it skins over.
Step 5 — Allow to Cure
Check the product's cure time — most sealants need at least 24 hours before exposure to water, and some need longer to reach full strength. Don't run water through the gutter or let rain hit the joint during this period if you can help it.
Gutter Joint Types: What to Expect
| Joint Type | Common Material | Notes |
|---|---|---|
| Slip joint (overlap) | uPVC, aluminium | Easiest to reseal; clean both overlapping surfaces |
| Union/connector piece | uPVC | May have a rubber gasket — check if gasket needs replacing |
| Soldered joint | Copper | Sealant is a temporary fix; may need a plumber or roofer |
| Riveted joint | Steel/aluminium | Seal around the rivet heads as well as the seam |
Note: If your gutter has a rubber gasket inside the joint, check whether the gasket itself has perished. If so, replacing the gasket (available at most hardware stores) will give a better long-term result than sealant alone.
Tips for a Long-Lasting Repair
- Don't rush the drying time — this is where most DIY repairs fail
- Apply sealant on a dry day above 10°C for best adhesion
- Clean your gutters at least twice a year (more if you have overhanging trees) to prevent debris build-up that accelerates joint failure
- Check gutter fall (slope) — gutters should slope gently toward the downpipe. Pooling water puts extra stress on joints
When to Call a Professional
Some gutter issues go beyond a simple reseal. Call a qualified gutter cleaner or roofing tradesperson if:
- The gutter is cracked, sagging, or pulling away from the fascia
- Multiple joints are leaking, suggesting the whole run needs replacing
- The leak is near roof flashings — this may involve the roof cladding and could affect your building's weathertightness under NZ Building Code clause E2
- You're not comfortable working at height
- The gutters are copper or older steel with soldered joints requiring specialist repair
A qualified local gutter cleaner or roofing tradesperson can be found on tradedirectory.co.nz. Getting a professional to inspect and reseal all joints at once can save you repeat trips up the ladder.
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