6 things your neighbour could be doing that are causing damp in your home – and what you can do about it

As we shift into autumn and the temperature drops, the chance of damp creeping into our homes rises. We close the windows, start drying clothes inside and pop the heating on. All of these elements together can increase the chances of damp, and whilst a dehumidifier is a great option, it's not solving the actual problem in this case.

The most common reason for damp appearing can be sharing a wall (or two) with a neighbour. This is called 'penetrating damp' and can be caused by a number of issues. Once established, it can spread and settle, so it's important at this time of year to be aware of the causes; as such, we have asked our experts what we should all be looking out for this season.

1. Leaking gutters

Leaking gutters are one of the biggest issues, and with leaves starting to drop, they're also getting clogged up.

Mark Irving, building expert at Build & Plumb, explains, 'If your neighbour has a leaking gutter, this can eventually lead to penetrating damp in your home due to the repeated overflow of water saturating external brickwork. Bricks, mortar and render are all porous, and they will soak up escaping water instead of allowing it to flow down the drainpipe. Over time, this moisture will build up and travel downwards or sideways through the masonry. If it hits a shared or adjoining wall, it will cross over onto your property and show up as damp.'

If you are suspicious of a leak, then a good option is to check the guttering when it's actually raining; this will show you whether it's overflowing or dripping onto brickwork.

Also check the downpipe. A blockage lower down can cause water to back up into the gutter and overflow even when the gutter itself looks fairly clear.

'If the same wall keeps becoming damp after rain, the guttering and downpipe are worth checking before assuming there is a plumbing leak somewhere inside the house,' advises Peter Jones, director at ADI Leak Detection.

Give your gutters the once-over; we love Amazon's 4m 13ft 2-in-1 telescopic gutter cleaning brush scoop kit, currently £25.64. You can operate from the ground so no need for ladders.

2. Plumbing leaks

These can come from various sources – a broken pipe, a leaking bath (if you live in a flat), appliances like a leaking washing machine, radiators and shared drains.

'A bathroom or kitchen on the other side of a shared wall can cause damp in your home if there is a leak behind it,' says Peter. 'It does not need to be a burst pipe. A small leak from a shower connection, bath, toilet or pipe joint can release water slowly over a long period without either household noticing straight away.'

A sign to look out for is if the damp gets worse even during dry weather. 'This means plumbing becomes more likely. You may also notice the patch changing after the bathroom or kitchen next door has been used, although it is not always that obvious,' Peter adds.

If you or your neighbour have a leaking pipe, then the 151 waterproof stop leak rubberised leak repair spray is a good quick fix, £6.94 at B&Q.

3. Damaged roofing

'The flashing on a roof seals the gap where your roof meets your neighbour's, or where a chimney joins onto a property,' explains Mark. 'If the flashing on your neighbour's side is damaged, cracked or missing, water can run straight down behind the brickwork and seep into interior walls.'

Slipped or broken tiles can also expose roof felt, Mark adds. 'If this felt is old or damaged, water running off the roof can be directed onto the brickwork of your property and cause damp in party walls or loft spaces.'

Laura Rich, former estate agent and property designer at Furniturebox, says to look for signs like brown or yellow staining, bubbling or flaking paint, or even the smell of damp. 'Mould growth or patches that become worse after rain is a sign that the roof tiles are problematic. If the damp is concentrated on a wall or ceiling directly adjacent to a neighbour's roof structure, it's worth considering whether the source could be external rather than assuming it's an internal plumbing problem.'

For an emergency roof issue, B&Q's liquid rubber roof coating leak seal will do the trick and is ideal for flat roofs too, £59.99 for 5 litres. It is definitely worth maintaining your roof and encouraging your neighbour to check theirs too.

4. Empty properties

Is the property next to yours empty? This can be fine during the summer months, but once the seasons change, problems can begin to show themselves, especially if the house is being neglected.

'A vacant property can pose more of a risk as problems may not be spotted as quickly; homeowners are likely to notice a dripping tap, leaking radiator, overflowing gutter or water stain much sooner than a property that is sitting empty,' says Laura. 'Properties that are unoccupied for an extended period might mean heating may also be switched off, ventilation may be limited and routine maintenance can be missed - contributing to moisture and condensation problems within the empty property.'

Of course, if the house is temporarily vacant but still maintained by the owner, it should be fine, but if not, it can be worth investigating. You can check ownership and occupancy records at HM Land Registry.

5. Garden issues

Perhaps not one we often think about, but it can be a cause. According to Mark, there are three main causes for concern.

'First up is if your neighbour raises the level of their garden soil, lawn or patio so that it is above your home's damp-proof course, moisture can bypass this barrier and soak into the brickwork of your home. The second is surface water run-off – sloped lawns, patios and concrete slabs that direct rainwater towards your property can saturate external walls and cause penetrating damp. The last is dense vegetation near a brick wall, as it will be constantly shaded and wet, which prevents water from evaporating; this increases internal condensation.'

A good time to check for these is after heavy rain. 'Look for water pooling beside the wall, water running from the neighbouring garden towards the property or one section of soil which stays wet much longer than everywhere else,' suggests Peter.

If your garden becomes waterlogged, the quickest solution is to spike it with a fork; this will help the standing water drain away.

6. Building work or structural changes to a neighbouring property

We know that building work near your property can create issues – it can move pests like rats, create foundation cracks, cause wall and roof damage due to heavy equipment vibration and add extra dust.

'Extensions, new paving, raised patios or changes to external walls can sometimes alter how rainwater drains around a property,' says Noel Folk, indoor air quality expert and founder of EcoAir. 'For example, if paving is raised too high against a shared wall or water is redirected towards your property, it can increase the risk of moisture getting into the walls.'

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You must check your home over for damp at this stage in the year, then keep looking over potential areas and put some preventative measures in place.