Renovating
How to Deal With Penetrating and Rising Damp
Think you might have damp in the fabric of your home? Check out our expert advice on managing this common issue
Flaky plaster, unexplained damp patch or strange stain troubling you? You’re not alone.
Penetrating damp is one of those common problems many homeowners in Britain deal with at some point – partly because it’s a fairly humid country, partly because many of us live in period homes, and partly because we aren’t always as diligent at house maintenance as we’d like to be. Leaky pipes, broken roof tiles and faulty pointing can all be a problem.
Here, three professionals explain what penetrating (and rising) damp is, how to identify it, how to get rid of it, and how to prevent it from coming back.
Professional advice from: Cat Hoad of Absolute Project Management; Lior Brosh of Brosh Architects, who specialises in period properties; John Klee, heating content specialist at BestHeating
More in this series: How to Deal With Condensation Damp
Penetrating damp is one of those common problems many homeowners in Britain deal with at some point – partly because it’s a fairly humid country, partly because many of us live in period homes, and partly because we aren’t always as diligent at house maintenance as we’d like to be. Leaky pipes, broken roof tiles and faulty pointing can all be a problem.
Here, three professionals explain what penetrating (and rising) damp is, how to identify it, how to get rid of it, and how to prevent it from coming back.
Professional advice from: Cat Hoad of Absolute Project Management; Lior Brosh of Brosh Architects, who specialises in period properties; John Klee, heating content specialist at BestHeating
More in this series: How to Deal With Condensation Damp
What are the signs?
Spied a worrying stain on your ceiling, or walls feeling clammy? It’s probably time to investigate.
“The first signs of penetrating damp are typically a damp area on a wall or ceiling that looks unsightly and which can lead to mould and mildew, or maybe a damp smell in a cupboard or behind furniture,” Cat says.
Lior says the typical signs are wet stains on walls, black mould, bulges in walls or loose plaster.
John Klee advises looking out for distorted, blistering or bubbling plaster. “Salting can also occur, leading plaster to appear white and fluffy,” he adds. “Skirting boards and floor timbers can also be seen to rot.”
Spied a worrying stain on your ceiling, or walls feeling clammy? It’s probably time to investigate.
“The first signs of penetrating damp are typically a damp area on a wall or ceiling that looks unsightly and which can lead to mould and mildew, or maybe a damp smell in a cupboard or behind furniture,” Cat says.
Lior says the typical signs are wet stains on walls, black mould, bulges in walls or loose plaster.
John Klee advises looking out for distorted, blistering or bubbling plaster. “Salting can also occur, leading plaster to appear white and fluffy,” he adds. “Skirting boards and floor timbers can also be seen to rot.”
What causes it?
If you have a large crack in your exterior render directly behind a growing interior damp patch, then the cause will be obvious. However, at other times it can be a headache pinpointing exactly where water is getting in – and it might require some detective work.
“Penetrating damp is usually caused by some lack of maintenance or a problem developing in a property, although the cause can be very simple – if the rainwater downpipe becomes blocked by autumn leaves, for instance,” Cat says. “The water that would have run away into the drain then runs down the surface of the brickwork. Over time, this gets soaked through and moisture penetrates to the inside of the house.”
But, as Cat points out, you won’t always have easy and safe access to the source of a problem, such as a blocked pipe. “You might need a specialist with a ladder or scaffolding,” she says. “That can be expensive, but the problem won’t go away till it’s fixed, and it could continue to cause deterioration.”
Lior points to damaged drains as a common cause of rising damp. “If pipes under the structure are damaged or broken, this allows water to sit under your house and undermine the foundations,” he says. “That creates movement in the bricks, which can cause cracks in the damp-proof course.”
If you have a large crack in your exterior render directly behind a growing interior damp patch, then the cause will be obvious. However, at other times it can be a headache pinpointing exactly where water is getting in – and it might require some detective work.
“Penetrating damp is usually caused by some lack of maintenance or a problem developing in a property, although the cause can be very simple – if the rainwater downpipe becomes blocked by autumn leaves, for instance,” Cat says. “The water that would have run away into the drain then runs down the surface of the brickwork. Over time, this gets soaked through and moisture penetrates to the inside of the house.”
But, as Cat points out, you won’t always have easy and safe access to the source of a problem, such as a blocked pipe. “You might need a specialist with a ladder or scaffolding,” she says. “That can be expensive, but the problem won’t go away till it’s fixed, and it could continue to cause deterioration.”
Lior points to damaged drains as a common cause of rising damp. “If pipes under the structure are damaged or broken, this allows water to sit under your house and undermine the foundations,” he says. “That creates movement in the bricks, which can cause cracks in the damp-proof course.”
For an initial diagnosis, Lior recommends looking at the direction in which the damp is travelling.
“If the damp seems to be coming down from above, it’s normally due to a faulty roof, a blocked or damaged gutter system, or damaged windows,” he explains. “If the damp is coming from the floor and rising up the walls, it’s normally due to a damaged drain system, damp-proof course or damp-proof membrane.”
Remember, also, that some types of chemical damp-proofing only last 20 to 25 years, not the lifetime of a property.
“If the damp seems to be coming down from above, it’s normally due to a faulty roof, a blocked or damaged gutter system, or damaged windows,” he explains. “If the damp is coming from the floor and rising up the walls, it’s normally due to a damaged drain system, damp-proof course or damp-proof membrane.”
Remember, also, that some types of chemical damp-proofing only last 20 to 25 years, not the lifetime of a property.
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What damage can it cause?
This will depend how long your damp problem hangs around, and the extent of any water penetration.
“Penetrating damp can cause really extensive damage in the long-term,” Cat says. “It can cause brickwork to deteriorate and crumble, or fall off. It can also cause timbers, such as on a windowsill or wardrobe, to rot and swell, and can rot fabrics such as curtains or carpet.” She warns that penetrating damp may also cause issues with electrics and electrical equipment, which is “potentially dangerous”.
Replastering, redecorating and replacing rotten windows may all be necessary if your problem is caught too late. In the worst instances, damage to property can be devastating, not merely cosmetic, Lior warns. “It can undermine the structure of the house by leading to the development of dry rot, which can turn brick into powder,” he says.
This will depend how long your damp problem hangs around, and the extent of any water penetration.
“Penetrating damp can cause really extensive damage in the long-term,” Cat says. “It can cause brickwork to deteriorate and crumble, or fall off. It can also cause timbers, such as on a windowsill or wardrobe, to rot and swell, and can rot fabrics such as curtains or carpet.” She warns that penetrating damp may also cause issues with electrics and electrical equipment, which is “potentially dangerous”.
Replastering, redecorating and replacing rotten windows may all be necessary if your problem is caught too late. In the worst instances, damage to property can be devastating, not merely cosmetic, Lior warns. “It can undermine the structure of the house by leading to the development of dry rot, which can turn brick into powder,” he says.
How can it be treated?
As you’d probably expect, the key treatment is getting rid of the cause of water penetration.
“The good news is, once the cause is eliminated and the affected areas are allowed to dry out, the damage can often be rectified quite easily and isn’t necessarily long-lasting,” Cat says. In less severe cases, it might be a case of patching up your paintwork or a little light skimming of the plaster.
If the damp is rising, you might need a CCTV drain survey, Lior says. If your damp-proof course is damaged, then bricks might need a special injected treatment to rectify problems, and special plaster applied on walls.
For a roof, John says the most common treatment will be applying a water repellent. He points out that, when it comes to cost, it’s almost impossible to name a price, as every cause of penetration damp will require a different treatment.
“Generally speaking, a damaged roof will be more expensive to fix than a leaking pipe or two,” he says. “A single double-glazed window replacement could cost anything from £200 to £500 before fitting.”
As you’d probably expect, the key treatment is getting rid of the cause of water penetration.
“The good news is, once the cause is eliminated and the affected areas are allowed to dry out, the damage can often be rectified quite easily and isn’t necessarily long-lasting,” Cat says. In less severe cases, it might be a case of patching up your paintwork or a little light skimming of the plaster.
If the damp is rising, you might need a CCTV drain survey, Lior says. If your damp-proof course is damaged, then bricks might need a special injected treatment to rectify problems, and special plaster applied on walls.
For a roof, John says the most common treatment will be applying a water repellent. He points out that, when it comes to cost, it’s almost impossible to name a price, as every cause of penetration damp will require a different treatment.
“Generally speaking, a damaged roof will be more expensive to fix than a leaking pipe or two,” he says. “A single double-glazed window replacement could cost anything from £200 to £500 before fitting.”
“The best way to stop this type of damp coming back is to be diligent with straightforward maintenance on your property,” Cat says. That means keeping on top of all those niggly jobs it can be easy to neglect, such as clearing gutters and keeping exterior decoration up to date. “Water can get into cracks in painted surfaces, such as window frames,” she says.
“The roof, guttering system and windows are the first line of defence against water penetration, so make sure all are in working order and check your gutters on a yearly basis for blockages,” Lior advises. “Inspect the external walls of your home by looking for damaged bricks or loose pointing. If it’s a period home, find a builder who has experience with old buildings.”
John advises paying attention to windowsills. “Ensure there’s no blockage in the drip grooves to avoid moss and dirt forming and expanding in these crevasses. If you do notice a build up of muck, thoroughly clean them.”
“The roof, guttering system and windows are the first line of defence against water penetration, so make sure all are in working order and check your gutters on a yearly basis for blockages,” Lior advises. “Inspect the external walls of your home by looking for damaged bricks or loose pointing. If it’s a period home, find a builder who has experience with old buildings.”
John advises paying attention to windowsills. “Ensure there’s no blockage in the drip grooves to avoid moss and dirt forming and expanding in these crevasses. If you do notice a build up of muck, thoroughly clean them.”
Anything else to know?
If there’s one golden piece of advice from all the experts, it’s this: don’t simply do nothing and bury your head in the sand.
“Don’t ignore a damp issue in your home,” Lior says. “If you notice any damp, I suggest contacting a specialist. There are many companies that do damp surveys to find out the causes and can propose the appropriate solutions.”
And while professional advice is vital, it’s always a good idea to apply a little common sense, too. “I lived in a flat that had water penetration on an outside wall; the plaster and paint inside was bubbling and flaking,” Cat says.
“Then one day in the street, I looked up and noticed an overflow pipe from the loo in the room above was dripping,” she says. “It turned out to be because of a slightly faulty ballcock in the cistern. We fixed that quickly and cheaply and the damp stopped. So sometimes you just need a bit of lateral thinking!”
Tell us…
Have you had penetration damp and did you manage to get rid of it? Share your advice and photos in the Comments.
If there’s one golden piece of advice from all the experts, it’s this: don’t simply do nothing and bury your head in the sand.
“Don’t ignore a damp issue in your home,” Lior says. “If you notice any damp, I suggest contacting a specialist. There are many companies that do damp surveys to find out the causes and can propose the appropriate solutions.”
And while professional advice is vital, it’s always a good idea to apply a little common sense, too. “I lived in a flat that had water penetration on an outside wall; the plaster and paint inside was bubbling and flaking,” Cat says.
“Then one day in the street, I looked up and noticed an overflow pipe from the loo in the room above was dripping,” she says. “It turned out to be because of a slightly faulty ballcock in the cistern. We fixed that quickly and cheaply and the damp stopped. So sometimes you just need a bit of lateral thinking!”
Tell us…
Have you had penetration damp and did you manage to get rid of it? Share your advice and photos in the Comments.
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The name might sound scary, but, from a technical point of view, penetrating damp is actually a relatively simple problem to understand.
“It’s dampness coming into a property from the outside,” Cat Hoad says. “It’s caused by a breach of the waterproof layer that protects buildings from the external elements. For example, it could be rainwater getting in through a leaky roof, or through a wall because of a faulty gutter – where, rather than flowing into the nearest drain, water is effectively directed against a wall or through cracks in brickwork, pointing, or around the edges of windows and doors.”
John Klee points out that penetrating damp by its nature can “infiltrate any part of a home at any level” and “detrimentally affect properties of any age”.
Rising damp is when water penetrates from below, usually because the building’s damp-proof membrane has been compromised in some way.
Lior Brosh explains that rising damp is more likely to happen in period buildings through some sort of defect in the build. “These buildings are commonly made of a mixture of bricks and timber,” he says. “When any existing damp-proof course is worn out or damaged due to movement, it allows water to climb up the internal walls.”