Heat Damage to Rental Properties: The Pre-Autumn Checklist for London Landlords

After the Heatwave: The Pre-Autumn Property Check Every South London Landlord Should Be Doing

Summer damage to a property is rarely dramatic. Nothing falls down in August. What actually happens is quieter: materials expand, dry out, shrink back and lose their seal — and none of it announces itself until the first serious downpour of autumn pushes water into a gap that wasn't there in June.

That gap between cause and symptom is exactly why we schedule inspections at this point in the year rather than in November. By the time a tenant reports a damp patch on a bedroom ceiling, the repair has usually stopped being a £200 job.

After another record-breaking run of heat, insurers are urging property owners to look over their buildings before the seasons turn. From where we sit — managing 124+ properties across Balham, Clapham, Tooting, Streatham, Dulwich, Wandsworth and Crystal Palace — that advice lands with particular force in this part of London.

Why South London landlords should take this more seriously than most

Much of our patch sits on London Clay. Clay is the soil type that responds most strongly to prolonged dry weather: it shrinks as moisture leaves it, and the ground beneath a building can move with it. Victorian and Edwardian terraces — the backbone of the rental stock in Tooting, Balham, Herne Hill and Streatham — often sit on shallow foundations that were never designed with that movement in mind. Add mature street trees drawing moisture out of the subsoil, and you have the classic recipe for subsidence.

The numbers make the case for looking early. Cracking that turns out to be structural typically costs in the region of £17,000 to put right, and the Association of British Insurers has reported average subsidence claims reaching around £20,000 this year. A full roof replacement averages roughly £8,000. Set against that, a slipped tile replaced in September is not really a cost at all.

There's a second reason to act now, and it's one landlords often overlook: insurers expect maintenance. Damage that develops gradually from a defect you could reasonably have spotted is one of the most common reasons a claim is reduced or declined. A documented seasonal inspection is not just good management — it's your evidence.

What we look for before autumn

You can pick up most of this from the ground with a decent pair of eyes and a torch. None of it requires a survey.

1. New or widening cracks

Check external walls, and internally around door frames, window reveals and where ceilings meet walls. Fine hairline cracking is common and usually cosmetic. What matters is a crack that is wider than about 3mm, wider at one end than the other, running diagonally, or visibly longer than it was in the spring. Those warrant a professional opinion rather than filler. Photograph anything you're unsure about with a coin or ruler alongside it — that photo becomes your baseline for next year.

2. The roof

Heat cycles expand and contract roofing materials, which loosens fixings and shifts tiles. Look from the street and from the garden for slipped, cracked or missing tiles, daylight visible through a loft, and the condition of flashing around chimneys, valleys and dormers. Flat roofs and single-storey rear extensions deserve a closer look — felt and EPDM harden and split under UV.

3. Gutters, downpipes and drainage

Plastic guttering softens in sustained heat, so sections sag, joints pull apart and brackets loosen. It rarely matters in August. It matters enormously during the first heavy rain, when overflowing water runs down the face of the wall and saturates brickwork and foundations. Clear the summer's debris while you're there, and check that gullies at the base of downpipes are running freely.

4. Brickwork and pointing

Sun and heat degrade mortar over time; it goes powdery, crumbles at the joint and eventually falls out. Missing pointing is a direct route for water into the wall, which shows up months later as penetrating damp on the inside — usually blamed, wrongly, on tenant condensation. Rake a key across a few joints on the most exposed elevation. If mortar comes away as dust, plan repointing.

5. Sealant around windows and doors

UV dries out silicone until it hardens, shrinks and pulls away from the frame. It's a five-minute check and one of the cheapest fixes on this list. Replacing perished sealant before autumn keeps out both rain and draughts — which, incidentally, helps on the energy efficiency front too.

6. Timber that has moved

Wooden doors and sash windows swell in heat and usually settle back as temperatures drop. If they're still sticking, binding or failing to lock properly by late September, the timber has likely warped. Worth resolving promptly: a front or back door that no longer closes and locks cleanly is a security issue, and in a tenanted property that is your responsibility, not the tenant's.

Turning the checklist into a system

For managed properties, this is the part that actually protects the asset:

• Inspect on a schedule, not on complaint. Two visits a year — one before autumn, one in spring — catch the vast majority of building faults while they're still cheap.

• Record everything. Dated photographs and a written report give you a defensible position with insurers, and a clear picture of whether a crack is moving or static.

• Tell tenants what to report. Most tenants will flag a leak. Far fewer think to mention a door that's started to stick or a gutter that overflows in heavy rain. A short, friendly note at the start of autumn is worth more than any clause in a tenancy agreement.

• Triage honestly. Sealant and slipped tiles are maintenance. Structural cracking is not — that needs a chartered surveyor and, potentially, an insurer notified early rather than late.

A note for flats, blocks and leaseholders

If your property is a flat, the roof, gutters, main structure and external walls are almost always the freeholder's or RTM company's responsibility under the lease — recovered through the service charge. That doesn't mean you can ignore them. It means the route is different: report the defect to the managing agent in writing, keep the correspondence, and follow it up.

Where we act as block managing agent, this seasonal inspection sits within our planned maintenance cycle. Where significant external works are needed, we'll also be looking at whether the cost crosses the Section 20 consultation threshold — because getting the consultation process right is what keeps those costs recoverable. Discovering the problem in September, rather than in the middle of a January leak, gives everyone time to do it properly.

Talk to us

If you'd like your property inspected before the weather turns — or you've noticed something on this list and aren't sure how serious it is — get in touch. We'll take a look, tell you plainly whether it's a maintenance job or something that needs a surveyor, and handle the works from there.

Your Home Managed Ltd — lettings, property management and block management across South and South West London.

We make it personal · Falamos Português Company No. 13118297

Sources for the figures quoted: insurer Quotezone's pre-autumn guidance for property owners and Association of British Insurers claims data, as reported by Landlord Today, August 2026.