Rising damp can quietly damage skirting boards, plaster and decoration long before most homeowners notice the problem. Catch it early and the repair is straightforward. Leave it, and the cost climbs.
This guide walks you through how to fix rising damp properly: how to confirm it’s actually rising damp (and not condensation or a leak), the treatment options that genuinely work, and what a proper repair looks like from start to finish. It’s written by the team at London Property Preservation, a family run damp proofing specialist that has been treating rising damp across South London since 1994.
What Is Rising Damp?
Rising damp is moisture from the ground travelling upwards through the porous materials in your walls, usually brick, stone and mortar. It moves by capillary action, in the same way water climbs up a paper towel dipped in a glass. The moisture typically reaches around a metre above the skirting board before evaporation balances the flow.
It is one of three main forms of dampness found in UK homes, and the trickiest to diagnose without proper training. The other two are penetrating damp (water entering horizontally through walls, usually from a defect outside) and condensation (moisture from inside the home settling on cold surfaces). Each one looks similar on the surface but needs a completely different repair, which is why a misdiagnosis often wastes thousands of pounds.
Rising damp is most common in older London properties, particularly Victorian and Edwardian homes where the original damp proof course has either failed, been bridged by later building work, or was never installed in the first place.
If you’d rather skip the reading and have an expert take a look, we offer free damp surveys across Croydon, Clapham and the wider London area.
Signs of Rising Damp
Before you can fix rising damp, you need to be sure that’s what you’re dealing with. Look for these signs together rather than in isolation, since any one of them on its own can point to a different problem.
On the wall itself:
- A tide mark or horizontal staining around 1 metre above the skirting board
- Peeling, bubbling or blown plaster at the base of the wall
- Damp patches that feel cool and don’t dry out, even in warm weather
- White, powdery deposits known as efflorescence, caused by salts pulled up through the brickwork
- Discoloured or lifting wallpaper along the bottom edge
- Flaking or blistering paint near floor level
On timber and decoration:
- Rotting or warped skirting boards
- Black mould appearing low on the wall (often the first thing people notice)
- Carpets or floor coverings feeling damp around the edges of a room
The smell test:
- A persistent musty, earthy odour, especially noticeable when a room has been closed up
If most of these signs sit at the top of a wall or around windows, you’re more likely looking at condensation or a roof issue. Rising damp almost always starts low and works upwards.
For more on telling these apart, our guide to how to identify damp walls breaks down each type in more detail.
Why Choose London Damp Solutions
If you’re in London and weighing up who to call, here’s what we bring to the job:
- Established 1994 – over three decades treating rising damp across South London
- Family run – you deal with the same people from first call through to final sign-off
- Approved Triton Contractors
- Members of the National Register of Property Preservation Specialists
- 4.7-star Google rating from clients across Croydon, Clapham and beyond
- Free damp surveys with a clear, written report
- 5% discount on any like-for-like written quote
We cover Croydon, Clapham and the wider South London area from our base at 13–15 Lancing Road, Croydon CR0 3EN.
What Causes Rising Damp?
Rising damp doesn’t appear out of nowhere. It almost always points to one (or more) of the following:
- A failed or missing damp proof course (DPC). Properties built before the 1875 Public Health Act often have no DPC at all. In newer homes, slate, bitumen or plastic DPCs can deteriorate or be damaged by structural movement.
- A bridged DPC. This is one of the most common causes we see. Raised garden beds, new patios, render carried down past the DPC line, or internal floors built up above the DPC all allow moisture to bypass the barrier.
- High external ground levels. UK building regulations require the DPC to sit at least 150mm above outside ground level. When landscaping, driveways or paths breach that gap, water finds a way in.
- Defective rendering or pointing. Cracked render and crumbling mortar joints let groundwater soak deeper into the wall.
- A blocked cavity. Rubble, mortar droppings or insulation that’s slumped over time can act as a wick, drawing moisture from the outer leaf to the inner.
Older South London housing stock is particularly vulnerable, which is why our damp specialists always start with a thorough on-site diagnosis rather than assuming the cause.
How to Fix Rising Damp: Step by Step
Treating rising damp properly is a sequence, not a single action. Skipping steps is the main reason it comes back. Here’s how a professional rising damp repair runs from start to finish.
Step 1: Get a Professional Damp Survey
Always start with a survey. A trained damp surveyor will use a calibrated moisture meter, check ground levels, inspect the DPC line, look for bridging, and rule out condensation and leaks. Without this, you risk treating the wrong problem.
A proper damp survey also tells you the extent of the damage to plaster and timber, which determines what repairs you’ll need after the damp itself is dealt with.
Step 2: Remove the Affected Plaster
Once rising damp is confirmed, the contaminated plaster needs to come off. This isn’t optional. Plaster that’s been soaked by rising damp holds hygroscopic salts, which keep pulling moisture from the air long after the wall has dried. Leaving it in place guarantees recurrence.
Plaster is typically removed to at least 300mm above the highest visible damp line, back to bare masonry.
Step 3: Install a New Damp Proof Course
This is the core of the repair. Modern DPC installation almost always uses chemical injection: a water-repellent cream or fluid is injected into a series of drilled holes along the mortar bed just above ground level. As it spreads, it creates a continuous chemical barrier that stops capillary moisture in its tracks.
In some cases, particularly where chemical DPCs aren’t suitable, a physical DPC (a slate or plastic membrane inserted into the wall) may be the better option. The right choice depends on the wall construction, and is something the surveyor will recommend.
If you’d like to understand the wider process, our damp proofing service explains how we approach each property.
Step 4: Allow the Wall to Dry
This is the step most DIY attempts get wrong. A wall doesn’t dry overnight. Even after a new DPC is installed, masonry can take weeks to months to release its trapped moisture, depending on wall thickness and weather conditions.
Improve airflow during this period, use a dehumidifier in the room, and resist the temptation to redecorate too soon.
Step 5: Re-plaster With a Salt-Resistant System
Once the wall is dry, it needs to be re-plastered using a specialist salt-resistant render and plaster system. Standard gypsum plaster applied to a wall that’s recently had rising damp will quickly fail. The render coat acts as a salt barrier, allowing the wall to breathe while keeping any remaining salts away from the finished surface.
Step 6: Address External Causes
Any external cause identified during the survey needs to be sorted, otherwise the new DPC is fighting a losing battle. That might mean lowering a path, removing a bridged render, repairing pointing, or improving drainage.
Step 7: Redecorate
Wait until the walls test dry before painting. Use a breathable emulsion for the first coat or two so any residual moisture can still escape. After that, normal decoration can resume.
How Much Does It Cost to Fix Rising Damp?
Rising damp treatment costs vary widely depending on:
- The length of wall affected
- Whether it’s an internal wall or an external one
- The amount of plaster removal and re-plastering required
- Whether external groundworks are needed
- Property type and access (a terraced Victorian in Clapham will price differently to a detached house with rear access)
Because of those variables, anyone giving you a fixed figure without seeing the property is guessing. We always quote after a survey so the figure you receive is the figure you’ll pay.
Rising Damp on Internal Walls
Rising damp on internal walls catches a lot of homeowners by surprise, because most people assume it’s only an external-wall problem. It isn’t. Any masonry wall in direct contact with the ground can suffer from it, including internal load-bearing walls and party walls in terraced and semi-detached homes.
The treatment process is the same as for external walls: survey, strip back, install a new DPC, dry, re-plaster. The only real difference is access. Internal walls often involve more disruption to flooring or skirting, so allowing extra time during the works is wise.
If you’ve got rising damp showing on both sides of an internal wall, it’s almost always a DPC failure rather than a leak, but a survey will confirm it either way.
Fixing Rising Damp in Older and Period Properties
A significant proportion of the homes we treat are Victorian, Edwardian or older. These properties need a slightly different approach:
- Lime plaster and lime mortar are often the right choice for re-plastering, as they let the wall breathe and suit the original construction
- Heritage considerations mean any work on a listed building or in a conservation area should be discussed with the local authority first
- Ground-level surveys are particularly important, as decades of landscaping changes have often raised exterior levels above the original DPC
We’ve been working on London’s older housing stock since 1994 and our damp specialists know how to repair these homes without compromising their character.
Frequently Asked Questions
Can I fix rising damp myself?
Some surface fixes (removing affected plaster, drying the wall, repainting) are within reach for a confident DIYer, but installing a new damp proof course really needs a specialist. Getting the injection depth, spacing or product wrong means the damp comes straight back, and DIY chemical DPC kits rarely come with the insurance-backed guarantee a professional install includes.
How long does it take to fix rising damp?
The DPC injection itself is usually a one-day job for an average room. The bigger time factor is drying: walls can take weeks to release the moisture they’ve absorbed before re-plastering is possible. Including the full repair and redecoration, allow four to eight weeks from start to finish for most homes.
Will my home insurance cover rising damp?
Most standard UK home insurance policies don’t cover rising damp, because insurers treat it as a gradual maintenance issue rather than a sudden incident. Always check your own policy wording. A leak that’s been mistaken for rising damp may be covered, which is another reason a professional survey is worth getting first.
Is rising damp actually real?
Yes. While a small number of voices online claim rising damp is a myth, it is a recognised building defect, well-documented in BRE (Building Research Establishment) literature and accepted by the wider construction industry. What is true is that it’s sometimes misdiagnosed – which is why getting a survey from a qualified damp specialist matters.
How do I stop rising damp coming back?
A properly installed DPC, paired with salt-resistant re-plastering and correct external ground levels, should keep rising damp away for decades. Annual checks of pointing, gutters and ground levels help. For a deeper guide, see how to stop rising damp.
Get Expert Help With Rising Damp in London
Rising damp doesn’t fix itself. The longer it’s left, the more plaster, timber and decoration it ruins, and the bigger the eventual bill. Catching it early means a quicker repair and a healthier home.
If you’ve spotted any of the signs above, the next step is simple: book a free survey and let one of our specialists confirm what you’re dealing with.
Book your free damp survey or call us on 020 8689 0073 – we’re open 8am to 4pm, Monday to Friday.
