Fix leaks, movement and moisture before resealing or regrouting
Wear gloves and eye protection. Stop if there is hidden water damage, persistent mould, structural movement or a safety-critical service penetration.
MOST LIKELY CAUSES
Start with these
Oversized penetration
The hole around the pipe was never sealed properly.
Failed filler or foam
Previous material has shrunk or broken away.
Air path through cavity
The gap connects directly to a void.
Pipe movement
Rigid filler has cracked around the pipe.
Symptom variations Match the exact failure pattern and location. ⌄
- Cold air around pipe
- Visible gap
- Dust movement
- Noise from cavity
- Previous filler cracked
Quick checks Simple checks before removing material. ⌄
- Check for leaks, damp or movement.
- Identify the existing sealant or grout type.
- Remove only failed material.
- Clean and dry the joint thoroughly.
- Choose a compatible flexible product.
Step 1 — Identify pipe type and temperature Remove failed material fully and use products suited to the joint, movement and moisture level. ⌄
Do not use unsuitable materials around hot pipes or flues.
Step 2 — Clean the gap Remove failed material fully and use products suited to the joint, movement and moisture level. ⌄
Remove loose filler and debris.
Step 3 — Seal with the correct flexible material Remove failed material fully and use products suited to the joint, movement and moisture level. ⌄
Use backing rod, sealant or approved fire-stopping where required.
Common causes explained Why sealants, grout and joints fail. ⌄
Draughts around pipes come from unsealed wall or floor penetrations, oversized holes or failed filler.
Advanced diagnostics Further checks for recurring failures. ⌄
- Check fire-compartment requirements.
- Use heat-resistant sealant near hot services.
- Avoid trapping condensation.
- Inspect cavity airflow.
- Do not seal boiler flues with general-purpose products.
Parts and materials needed Common materials linked to this repair. ⌄
- Flexible sealant
- Backing rod
- Fire-rated sealant where required
- Low-expansion foam
- Pipe collar
When to call a professional Conditions that should end basic DIY work. ⌄
- Water is leaking into walls or floors.
- The joint keeps opening because of movement.
- Mould or damp is widespread.
- An unvented cylinder, flue or fire-stopping joint is involved.
- Tiles or fittings are loose or unstable.
Frequently asked questions Common sealing and grouting questions. ⌄
Can new silicone be applied over old silicone?
No. Remove the old material and residue first for a reliable bond.
Should corners be grouted or sealed?
Changes of plane usually perform better with a suitable flexible sealant.