Why old roofs leak first – and what to check inside

In a cosy rural home, the roof is your first line of defence. Old buildings settle and shift, and their slates, tiles and flashing tire over decades. A slipped slate might seem trivial from the ground, yet it can let in a surprising amount of water. That water rarely appears as a dramatic drip. More often it creeps along a rafter, soaks into plaster and shows up as a brown patch on a bedroom ceiling weeks later.

Start indoors. After heavy rain or a storm, check upper rooms for faint damp stains, bubbling paint or a musty smell. In the loft, use a torch to inspect the underside of the roof covering and the rafters. Look for dark damp patches, white salt deposits or daylight through the roof. If you can see daylight, you have found a gap – and a likely entry point for water.

Safe inspection from the ground and the loft

Please do not climb onto a wet or frosty roof. A fall is far more serious than a leak. Use binoculars from the garden instead. Look for slates that have slipped out of line, cracked or missing tiles, and wobbly ridges. Check the chimney stack for cracked mortar and lifted lead flashing. Note anything suspicious, then check it from the loft if you can reach it safely.

In the loft, take a powerful torch. Look at the roof battens – the horizontal timbers holding the slates. Damp or blackened battens tell you water is getting in regularly. Check around chimneys, vents and roof windows. If you find a drip during rain, place a bucket underneath and take a photograph. This helps a roofer find the fault quickly, saving you money.

Slipped and cracked slates: the quiet culprits

Slates are held to battens by nails or hooks. Over time, nails rust and fail, especially on the sunny side of a roof where frost and heat cause constant movement. A slate can slip down and leave a gap, or crack after a hard frost. Water then runs behind neighbouring slates and into the roof space.

For a single slipped slate, a roofer can often re-hang it using a stainless steel slate hook or copper wire, without disturbing the rest of the roof. If the slate is cracked, replace it with a matching reclaimed slate. Do not simply push it back – the nail holes will be enlarged and it will slip again. Ask your roofer to check the battens and felt underneath while they are up there. On older roofs without felt, a small area of breathable membrane can be slipped in as a precaution.

Blocked valleys, gutters and hidden dams

Valleys are the sloping channels where two roof sections meet. They gather moss, leaves and twigs. When a valley blocks, rainwater cannot escape. Instead it backs up under the slates and into the building. This is a common cause of damp in rural homes surrounded by trees.

Clear valleys and gutters at least twice a year – in late spring and late autumn. Use a gutter scoop or a gloved hand, and work from a stable ladder with a helper. Never lean out over the gutter. Check that downpipes run freely. If a gutter overflows during rain, clear it. A blocked gutter can soak the wall, causing damp patches and crumbling render – far more expensive than a simple clean.

Worn flashing and mortar: the usual suspects

Flashing is the metalwork sealing joints between your roof and chimneys, walls, vents or dormers. On old buildings this is often lead. Lead lasts for decades, but it can crack, lift or become porous. Mortar pointing around chimney stacks also crumbles after frost.

Inspect flashing from the ground with binoculars. Look for gaps, lifting edges or tears. Do not cover cracks with silicone sealant. It is a temporary bodge that traps moisture and makes a proper repair harder. A roofer will replace damaged lead with new lead of the correct code – usually code 4 or 5 – and dress it neatly into the mortar. For old buildings, repoint with a lime mortar mix, not hard cement, so the chimney can breathe. White stains on brickwork below a chimney often mean water is tracking through failed mortar.

When to call a roofer – and how to prevent repeat problems

Call a professional roofer if you find multiple slipped slates, a sagging roofline, water near electrical fittings, or damp that returns after rain. Storm damage should be assessed quickly, as a small gap can let in litres of water in one downpour. A reputable roofer will survey the roof and give a written quote.

Prevention is simple. Check your roof from the ground after every gale, keep trees trimmed back from the roofline, and clear gutters and valleys twice a year. A stitch in time is never more true than on an old roof. By spotting cracked slates, blocked valleys and worn flashing early, you protect your cosy home from damp ceilings and expensive structural damage. Your roof has sheltered you for generations – a little care now will keep it doing so for many more.