Winter-proofing London property: the October checklist

Every January our emergency board tells the same story: frozen condensate pipes, burst supplies in cold lofts, gutters that finally surrendered. Almost all of it was preventable in October. This is the checklist we run for subscribers each autumn, published in full, with the reasoning behind each job so you can prioritise honestly if you only get through half of it.

Start at the roofline

Gutters and downpipes blocked with autumn leaf-fall will overflow in the first sustained rain, and in London's terraces that water usually finds a parapet junction or a window head. A clearance visit costs a fraction of the redecoration it prevents. While access is up there, have slipped slates, cracked fillets and flashings checked; small defects become ceiling stains under winter rain, and the gap between a ten-minute refix and an internal repair is one storm.

Parapet and valley outlets deserve their own line on the list. Unlike an eaves gutter, which overflows harmlessly outward, a blocked parapet outlet ponds water against the fabric of the building until it finds a way in. On flat roofs, clear the outlets and check that nothing has been stored or dropped on the membrane through the summer.

The heating system, before the first cold weekend

Boilers fail on the first cold weekend of the year because that is the first time they work hard since spring. An autumn service catches weak components before the December queue forms, and it is also when the engineer checks the flue, the pressure vessel and the safety devices that quietly drift out of spec. For rented property the service can share a visit with the annual gas check, which halves the access problem.

Three smaller jobs travel with the service. Bleed radiators and rebalance where rooms heat unevenly. Check the system pressure and teach the tenant where the filling loop is. And if the boiler is a condensing model, insulate the external condensate pipe: when that small white pipe freezes, the boiler locks out, and this single cheap fix addresses the most common winter breakdown in the country. If the pipe has frozen before, ask about rerouting or upsizing it rather than insulating and hoping.

Water: lagging, stopcocks and empty properties

Water is the other threat, and it rewards preparation more than any other system. Lag any pipework in lofts, garages and unheated voids, including the cold feed and vent pipes that older systems run through the loft. Find the stopcock, make sure it actually turns, and make sure the tenants know where it is: the difference between a damp cupboard and a collapsed ceiling is usually response time, and nobody finds a stopcock for the first time calmly at two in the morning.

Empty properties need a decision, not luck. Either keep background heat on through the cold months, or drain the system down properly. Check the insurance policy while you decide: most unoccupancy clauses impose conditions (minimum heating, regular inspections, water off) that quietly void cover when ignored, which turns a burst pipe into an uninsured burst pipe.

Condensation season

From November, condensation overtakes leaks as the source of damp complaints. Cold external walls, warm moist air and closed trickle vents produce mould on the coldest surfaces, usually behind furniture and in corners, and the standard January argument about lifestyle versus building defect helps nobody. Get ahead of it: check extractor fans actually run and vent to outside, confirm trickle vents are open, and brief tenants on the unglamorous basics of lids on pans and windows cracked after showers. Where a room moulds every winter regardless, treat it as a building signal (cold bridging, failed insulation, blocked airbrick) and investigate rather than repaint.

The stakes on this one have risen. Expectations on how quickly landlords respond to damp and mould reports have hardened across the rental sector, and a documented response (inspection booked, cause identified, works scheduled) is now the minimum defensible standard. An October ventilation check is cheaper than a February dispute.

Flats and blocks: the shared-fabric problem

Flats add a category of winter risk that houses do not have: the failure that starts in someone else's demise. A frozen pipe in an absent neighbour's flat, a communal loft tank with no lagging, a shared valley gutter nobody owns. If you let flats, establish before winter who maintains the communal fabric and how out-of-hours problems get reported to the managing agent, and put those contact details in the tenant's welcome pack next to the stopcock location. For top-floor flats, confirm the loft above is insulated and that any tank and pipework up there is lagged, because the flat below the loft is where the ceiling comes down. Leaseholders should also check what their lease and the block policy say about escape-of-water excesses, which in some London blocks now run to four figures and land on the flat where the leak started.

The outside walk

Finally, walk the outside with a critical eye. Overhanging branches, loose aerials and tired fence panels all become projectiles or leaks in a named storm. Check that gully gratings are clear so surface water drains away from the building rather than against it, that external taps are isolated or insulated, and that any garden furniture and planters are either secured or light enough not to matter.

Basement and lower-ground flats deserve one extra check: the condition of any anti-flood valve and the clearance of lightwell drains. Leaves collect in lightwells all autumn, the first real downpour finds the blocked outlet, and the water has nowhere to go but under the door.

The checklist, in order

• Clear gutters, downpipes and parapet or flat-roof outlets.
• Inspect the roof for slipped slates, cracked fillets and failed flashings.
• Service the boiler; bleed and balance radiators; check system pressure.
• Insulate (or reroute) the external condensate pipe.
• Lag pipework in lofts, garages and unheated voids.
• Locate and test the stopcock, and tell the tenants where it is.
• Set the empty-property plan: background heat or full drain-down.
• Check extraction, trickle vents and airbricks before condensation season.
• Walk the exterior for branches, aerials, fences and blocked gullies.

When to book it

October, and the reason is queues rather than weather. Roofers, heating engineers and drainage teams all hit capacity in the first cold snap, and emergency pricing follows demand. The same jobs booked in October happen at planned-work prices with planned-work care. GEM subscribers have this checklist run for them as planned autumn maintenance, with photographs filed against each property; for everyone else, print it, book the trades early, and enjoy a quieter winter.

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