What is penetrating damp? Signs your house may have it and how you can fix it, according to experts

Penetrating damp is a costly problem, so early detection is key

Pale grey green house exterior
(Image credit: Future PLC)

Wet and damp conditions are all part and parcel of living in the UK, but penetrating damp isn’t something you should take lightly. Left untreated, it could spell disaster for your home and cost you a fortune in maintenance and repair costs. But what is penetrating damp?

Not to be confused with the signs of rising damp, penetrating damp is when water sneaks into a property through its external walls. In an ideal world, homeowners want to get rid of damp and keep excess moisture to a minimum, which is why penetrating damp poses such a problem. 

The key to solving penetrating damp is early detection, which is why we’ve asked the experts to share their knowledge on what causes penetrating damp, how to identify it , and what to do if you have penetrating damp. 

What is penetrating damp?

Most people want to stop dampness coming through walls, but that’s impossible to do when you have penetrating damp. Below, we’ve outlined everything you need to know about this household problem, and what to do if you discover you have penetrating damp in your home. 

What causes penetrating damp

Penetrating damp can be a nightmare for homeowners and landlords alike, but it’s important to note that it's usually the by-product of a much bigger issue.

‘The usual suspects behind this problem include leaky roofs, cracks in walls, messed-up gutters, and faulty window or door seals,’ says Elizabeth Vergara from Vergara Homes

These external defects offer gateways for the water to infiltrate your home, which is why it’s always a good idea to keep on top of cleaning your gutters and keep an eye out for any cracks in your bricks or render or problems with your roof. 

Pale grey green house exterior

(Image credit: Future PLC/Rachael Smith)

Of course, penetrating damp is particularly troublesome during periods of heavy rainfall and is more common in older properties that have deteriorated over the years. It’s less common for modern homes to suffer from this problem, but there’s no doubt that it’s very inconvenient and costly for any house.

Jack Garratt, Managing Director at Garratt’s Damp & Timber Ltd says, ‘Penetrating damp may also affect your house insurance. Many insurance companies regard penetrating damp as general wear and tear, which means that any repairs are not covered, and the expense has to be covered by the homeowner.’

The signs of penetrating damp

Although penetrating damp can be a cause for concern, the signs of this excess moisture are primarily visible signs - which means that you should be able to catch them early. 

‘It manifests itself through visible damp patches, puddles and drips that are contained within a singular area,’ says Jack. ‘It makes plaster crumbly and wet, leaves damp patches on ceilings or walls, and staining on external walls.’

‘If left untreated, black mould or spores may appear on internal walls, as condensation increases due to the damp air hitting cold surfaces. It also has a distinctive musty odour, particularly when fungal growth of wet or dry rot occurs on the timbers.’

So, it’s best to keep an eye on your home and make a note of any unusual changes. 

white dehumidifier next to damp wall

Penetrating damp on kitchen wall

(Image credit: Future / Rebecca Knight)

What to do if you have penetrating damp

Although many people may dismiss the signs of penetrating damp, it’s important to solve this issue as soon as you spot them. 

Peter Clayton, from Trade Plumbing says, ‘When left untreated, penetrating damp can become very serious. Not only can it cause irreparable and costly damage to the structures of your home, but it may also result in the formation of mould on surfaces.'

First and foremost, you should try and do everything you can to dry the excess moisture that’s made its way into your house. The best way to do that is to use one of the best dehumidifiers

A Meaco dehumidifier by the side of a sofa in a living room with dark walls

(Image credit: Future / Heather Young)

Then, you need to find the cause of this penetrating damp. However, you should never try to carry out any remedial work yourself as you may cause more damage in doing so. Instead, do your research and find a well-respected and well-reviewed damp specialist who can take over. 

This professional will be able to survey your house and perform certain tests on the brickwork and the roof to see where the water is coming in. When they figure out where the water is coming in (in many cases, you may have a few separate issues that need fixing), they can take steps to repair the problem and protect your house from future penetration. 

You may find that your penetrating damp can be fixed with a few simple roof repairs, or it might be that you need to replace your broken gutters. However, you also need to be aware that this may be a much bigger job - especially if you need to re-render your house, weatherproof your bricks, or replace your windows. 

Peter adds, ‘Then, internal dampness can be treated. Damp plasterboard must be removed and left to fully dry. If the plasterboard is extremely wet or contains mould, it must be discarded and replaced.’


How do you know if damp is penetrating?

There are three different types of damp; condensation damp, rising damp and penetrating damp. Condensation damp is usually temporary and harmless, and rising damp will only ever affect the ground floor of your home. 

However, penetrating damp can affect any room in your house and is the result of water sneaking into a property through its external walls. This will usually show itself in the form of mouldy damp patches on your wall, a musty smell, and blistering plaster and paint. 

How do you treat penetrating dampness?

It’s always best to avoid DIY treatments when it comes to penetrating damp, as you may do your house more harm than good. But when a professional takes on this job, they will focus on treating the cause of this problem. This might involve fixing broken guttering, re-rendering the outside of a house, fixing masonry, or replacing broken roof tiles. 

The damp professional may also suggest weatherproofing the exterior bricks of your house, in an effort to create a weatherproof barrier between you and the outside world. 

If you spot signs of penetrating damp, it’s best to act fast. 

Lauren Bradbury

Lauren Bradbury is a freelance writer and major homes enthusiast. She graduated with a Bachelor’s degree in English and Creative Writing from the University of Chichester in 2016, before dipping her toe into the world of content writing. After years of agency work, writing everything from real-life stories to holiday round-ups, she decided to take the plunge and become a full-time freelancer in the online magazine world. Since then, she has become a regular contributor for Real Homes and Ideal Home, and become even more obsessed with everything interior and garden related. As a result, she’s in the process of transforming her old Victorian terraced house into an eclectic and modern home that hits visitors with personality as soon as they walk through the door.