How to Insulate Your Pipes to Prevent Freezing

When water freezes inside pipes, it expands and can crack or burst the pipe — causing flooding when it thaws. Lagging (insulating) vulnerable pipes is a simple, cheap preventive measure.

Which pipes are most at risk?

• The condensate pipe from your boiler (exits through an outside wall)
• Pipes in unheated spaces: loft, garage, outbuildings
• Pipes running along external walls with poor insulation
• Any pipework in unheated utility rooms

What you need

Foam pipe lagging — available from any DIY store (B&Q, Screwfix, Wickes) for approximately £1–3 per metre. It comes in different internal diameters — measure your pipe diameter first (most domestic pipework is 15mm or 22mm).

How to fit pipe lagging

1. Measure and cut the lagging to length with scissors or a knife
2. Open the pre-cut slit along the length of the lagging
3. Press it onto the pipe — it clips around the pipe and holds itself in position
4. At joints and bends, cut the lagging at 45° angles to make neat mitre joints
5. Secure with self-adhesive tape if needed in windy or high-access areas

The condensate pipe

Priority number one is your boiler's condensate pipe — the plastic pipe exiting through the wall that drains condensate from your condensing boiler. Wrap the full external section with foam lagging. This prevents the most common winter boiler lockout cause and takes 10 minutes.

If a pipe has already frozen

Do not use a blowtorch. Use warm (not boiling) water, a warm damp towel, or a hairdryer on a low setting to thaw slowly. Check for any resulting leaks once thawed before the system is used again.