When we hear the word “Damp”, we imagine difficult and costly procedures, together with chaos in the home as a professional fixes the problem. Fortunately, damp in the home is quite common and we have many tried and tested remedies available to use. Furthermore, the cost of damp proofing internal walls, as well as external, isn’t as bad as you might think.
The ancient Romans incorporated damp courses in their homes made from lead, slate or bitumen. However, in the UK it wasn’t until the 19th Century that they started using slate and bitumen impregnated hessian as a DPC.
But, these days, all modern houses use a plastic waterproof membrane to prevent moisture from soaking into the brick from the ground. Furthermore, houses also have a cavity wall to prevent rain from getting through the outside wall onto the inner wall surface where it damages plaster and interior fittings. Fortunately, the simple fixes employed by tradesmen are usually fairly inexpensive and quite adequate to sort out most problems.
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Crumbling masonry and rotten wood
There are three types of damp present in the average British home. And, each one has its specific cause and remedy. But, we’ll talk about these in more detail later. For now, let’s just say that each one will damage your decoration and furnishings if you leave them unchecked. And, if you don’t fix them at all, you can eventually have a house with rotten structural woodwork and crumbling masonry. Neither of which is a situation you want to happen. In short, your home will lose value very quickly and may need a complete re-build to restore it to its former glory.
The cost of damp proofing walls will depend on what type of damp it is, and what’s causing the problem. At the very least, if the problem is condensation all it’ll take is a change in lifestyle, which costs nothing. But, if it’s rising damp you can expect to pay from £400 up to £15,000, depending on the severity. However, bear in mind this cost includes replastering and redecoration, which you might be able to get done cheaper from a local handyman.
This guide sets out to explain:
- What the damp problems are.
- How to go about fixing damp in general, together with preventative measures.
- How much it’ll cost.
- You’ll learn why you should hire a professional to cure the rising damp.
- What is a damp survey?
- Identifying the signs of rising damp.
- How to treat damp internal surfaces.
- How to prevent penetrating damp.
With this safely under your belt, you can get back to living in your cosy damp-free home.
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Main Topics
Common Types of Damp
The three types of damp are:
1. Rising damp
Moisture in the earth soaks into the foundations and rises through the brick walls until it reaches your living space. Usually, houses have a damp proof course (DPC) through which water can’t travel. In old houses, they incorporated layers of slate as the DPC during construction. But, these days, we use a plastic membrane to prevent water from getting through.
If the DPC has failed, punctured, or split, it can be a difficult job to repair or replace. So, the commonest treatment for repairing damp proofing is to inject a chemical (usually a silicone compound) into the brick at DPC level. Then, remove the internal plaster, allow the wall to dry, followed by applying a damp proofing paint, or ‘tanking the walls’ as it’s known in the trade. Sometimes, the garden soil bridges the DPC. Now, you might not think this is important. But, the wet soil, piled up against the outside wall above the DPC, allows the moisture to soak in. This is simple to resolve. Remove the soil away from the wall, and perhaps lay paving slabs.
If you have an underground cellar, you’ll find that the walls will soak up moisture from below and outside, causing damp on the inner cellar wall. Usually, the remedy for this is to excavate and expose the outside of the cellar, inject a DPC and tank the walls up to DPC level to prevent moisture from penetrating. Then once the inside has dried out, apply damp proof plaster and salt neutraliser to remove any remaining signs of damp.
2. Penetrating Damp
Water from the outside seeping through the walls causes this type. Usually, the commonest causes are a cracked roof tile, damaged brickwork, broken gutter, or faulty window and door seals. Once the professional identifies the cause, it’s usually a case of repairing the fault for the dampness to disappear. However, in the meantime, mineral salts which have reacted with the water will appear on the surface. These can be brushed away and treated with a salt neutraliser.
3. Condensation
This type occurs in most houses, especially in modern ones with no draughts. This is the most common type of damp, but fortunately, is also the easiest to overcome. It’s caused by water–laden air meeting a cold wall, or ceiling. The condensed water soaks into the surface, leading to mould and mildew growth. It’s common in kitchens, bathrooms and wherever you dry wet clothes. In fact, anywhere you produce a lot of steam and water vapour. Modern homes with their good insulation and draughtproofing tend to produce areas of still air which makes the problem worse. To prevent this from happening needs a lifestyle change. Ensure you open windows and allow the damp air to escape, look behind wardrobes and cupboards for black patches and wipe down with diluted bleach.
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How much does rising damp treatment cost?
The cost of repairing a damp problem in your home will ultimately depend on the scale of the problem, how the problem came about, the size of your property, and how easy it is to fix the problem. The commonest cause of rising damp is where the outside ground level is above the level of the DPC. All you need to do is excavate the soil to at least 150mm below DPC level. Remember that these prices exclude VAT and will be about 15 to 20% higher if you live in or around London.
| Property type | Single wall | Whole house |
|---|---|---|
| Terrace house | £250 | £300 |
| Semi-detached | £250 to £300 | £600 |
| Detached | £500 minimum | £1500 |
If you live in an older property, you probably won’t have a DPC, or it’s made from bitumen impregnated hessian that deteriorates over time. To prevent damp, you must insert a modern DPC.
Injecting a silicone liquid under pressure is the easiest method. It soaks into the brickwork and mortar where it cures leaving a water–impermeable barrier. The following table gives an idea of the costs involved in DPC injection.
| Property type | Single wall | Whole house |
|---|---|---|
| Terrace house | £300 | £400 |
| Semi-detached | £400 | £900 |
| Detached | £650 minimum | £2000 |
You will also pay VAT on top. And, you will usually have to hire a plasterer and decorator to remedy damp damage.
In comparison, condensation and penetrating damp cost very little to remedy.
- Penetrating damp requires the gutter or window seal to be mended, along with damaged internal plaster. Probably, this will cost about £150 to £200 per day for a suitable tradesman.
- Condensation needs some ventilation and adequate heating in the house. This won’t cost anything as you’re doing it yourself.
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Damp Proof Course (DPC): Types & Prices
A damp proof course is a barrier that prevents the passage of water through the building. Usually, a bricklayer incorporates a DPC into a wall as it’s being built. But, it can be retrofitted at DPC level as an injected liquid if necessary by specialist contractors. In theory, you can use any waterproof material as a DPC. But, in practice, it must be able to withstand compression under the load imposed by the wall. Traditionally, bricklayers used a layer of slate, lead or bitumen as a DPC, which although adequate for the period, tended to become damaged with age. Nowadays, we use a structurally stable plastic sheet or injected chemicals.
Damp meter
Initially, you’ll need to know if you have damp problems. There’s a useful tool on the market called a Damp and Moisture Meter. It measures the conductivity of the brickwork between two points and calculates the amount of damp you have. Unfortunately, it won’t prove you have rising damp, only that you have damp areas that should be looked at further. It operates with wood as well as masonry, so can be used for other applications too. A simple DIY moisture meter costs about £20, but you can buy sophisticated professional versions costing up to £150.
Injected DPC
The cost of a damp proof course injection varies depending on certain factors. But, in general for a typical house will range from about £500 to £2000.
DPC Cream
Damp proof course cream is a DIY version for retrofitting. It consists of an aerosol can which injects the chemical into pre-drilled holes. A can of cream costs about £17 for 310ml, which covers about 1.6m.
DPC Rods
Damp proof course rods are another DIY solution. First, insert the rods into predrilled holes. Once in place, they release a liquid chemical DPC that seeps along the mortar course. They cost about £20 for a pack of 10 rods, which will cover 1.2m wall length.
Retrofitted DPC
There are different types of retrofitted DPC.
- We’ve already mentioned damp proof course injection. You inject a silicone–based liquid into predrilled holes. Then, the liquid penetrates the masonry, where it sets, creating a waterproof barrier. Costs vary from £500 to £2000.
- Mortar injection DPC is a mortar consisting of Portland cement, quartz sand and a mix of active chemicals. Mix it with water and inject into predrilled holes using a grout pump. A chemical reaction takes place, causing a network of crystals to grow. Effectively blocking any cracks and pores. A 20kg bag will cost you between £50 and £60.
- Electro-osmotic DPC might be the high-tech method we’ve all been waiting for. A few different companies provide kits, but they give the same basic instructions. Insert titanium electrodes into the wall just above ground level. Then, apply a small electric current from the mains supply. This, supposedly prevents the water molecules from rising up the wall as they’re attracted towards the negative electrode. However, many damp proofing surveyors question the validity of this method. You see, water molecules have no charge, meaning they won’t be attracted to any electrode. Heritage House quote communication from BRE in which they state that the systems are a failure and do not work. The Building Research Establishment (BRE) is considered to be the last word in building products certification in the UK. So, before you choose, do a lot of research, contact BRE and Trading Standards and decide for yourself whether you want to try this method.
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What Causes Damp Walls? (Interior & Exterior)
Any excess moisture can cause damp walls. Let’s just run over a few common scenarios.
Condensation comes from water vapour in the air condensing onto a cold surface. If you leave it, you will encourage the formation of mould. It’s very common in kitchens, bathrooms and around windows and doors.
Penetrating damp comes from water penetrating the outside skin of a cavity wall. Crossing the cavity and soaking through the internal skin and plaster. It can be caused by problems with guttering, cracks in masonry and rubble inside the cavity wall.
Rising damp comes from moisture travelling up the wall under capillary action from the ground. Normally, a DPC will stop this movement. But if there’s damage to the DPC or if outside ground level is too high, the barrier won’t operate properly.
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Identification & Signs
Usually, the commonest signs of rising damp are:
- Rotting skirting boards and plaster.
- Wet patches on the walls.
- Peeling wallpaper and paint.
- Crystallised salts appearing on the surface of the wall. These are minerals dissolved from the ground or brickwork and appearing on the surface.
Rising Damp Prevention: Steps You Can Take
First, find out where it’s coming from.
Find out if you have a DPC in your home. An old stone–built property probably won’t have one. Otherwise, find the DPC which should be about 150mm above outside ground level.
Follow the DPC around the house. Inspect it all the way and decide if it looks damaged or if it’s being bridged by structures. This can be flower beds or outside steps above the DPC level. It might also be interior plaster that touches a solid concrete floor.
Do you live in a semi–detached or a terraced house? If so, is it coming in from your neighbour’s house? And, is their DPC higher than yours.
You might have rubble inside the cavity that allows water to rise above the DPC level.
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Damp Surveys
A damp survey is a specialist inspection of a property done by a qualified damp surveyor. As a specialist, the surveyor knows what to look for and where. They will first ask questions about any damp, you might have found. Then, they’ll systematically go through the house, looking at certain places and checking the level of damp in the plaster using a damp meter. They will also look for possible future causes of damp, such as damaged guttering, objects bridging the DPC, and the condition of any pipework. Most damp surveys take no longer than about 4 hours. However, depending on various factors this might extend to be as much as a couple of days.
Factors include property size; the method of building the property; the extent of the damp problem; type of damp present; the extent of the damage and accessibility.
Eventually, you’ll receive a copy of the report discussing the findings and ways to remedy the damp. A typical damp survey will cost anything from £150 to £400 for a 3 bed detached property, depending on the size of the house and its location. The price is typical of the amount charged by a fully qualified chartered surveyor belonging to the Royal Institution of Chartered Surveyors.
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Does my tradesperson require any qualifications, be part of any trade bodies or associations?
Assessing and treating damp can be a tricky job. So, you’d expect the technician to be qualified and a member of a trade association.
A typical damp proofer will belong to a trade body such as the Damp Proofing Association, the Property Care Association, British Wood Preserving and Damp Proofing Association or the UK government endorsed TrustMark Scheme.
Additionally, the contractor should have a minimum of the following qualifications and certificates:
- Certified Surveyor in Remedial Treatments (CSRT).
- Construction Skills Certification Scheme (CSCS).
- Certificated Surveyor in Structural Waterproofing (CSSW).
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Hiring a Professional vs DIY
It’s always better to use a professional for serious things such as damp proofing. You’ll have a guarantee for their work, and the professional will spot things that you might miss. You’ll have the benefit of many years experience and their various professional training courses. A professional will know the ways to solve a damp problem and will know how to handle the various chemicals and equipment needed.
However, there are some damp problems that you can fix with a minimum of tools and experience.
- Removing soil from above the DPC will prevent damp from bridging the course.
- Repairing a broken gutter.
- Repointing brickwork.
- Applying mastic around a window.
All these are jobs that a DIY enthusiast can easily do. And of course, almost anyone can ventilate a room to prevent condensation.
But, if after trying these simple remedies, you still have a damp problem. You must contact a qualified damp proofing surveyor for a full inspection.
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Damp Proofing Cost FAQs
Is damp covered by insurance?
Not usually! Most home insurance policies (buildings and contents) will not give cover for problems caused by damp or condensation. However, some insurance companies will give specific cover for rising damp. But, you’ll probably have to pay a higher premium. Instead, it’s much better to keep on top of the maintenance jobs around the house, to reduce the likelihood of damp in the first place.
How long does damp proofing take?
This depends on the extent of the job and the size of your property. A small job will take from 1 to 2 days whereas a larger job will take about a week. However, as an average, a full damp proofing on a 3–bedroom semi–detached will take about 3 to 4 days.
How long after damp proofing can I paint?
After damp proofing, you should give the walls a chance to dry out naturally. This means that you should avoid decorating using wallpaper for about a year afterwards. However, you can use a water–permeable emulsion paint once all the visible signs of damp have gone. This will usually be between 1 to 2 months.
What happens if you leave rising damp untreated?
If you don’t treat rising damp, you’ll eventually end up with structural problems. The plaster will crumble away from the walls, woodwork will rot and paint will peel from surfaces. On top of that, you’ll have an unpleasant smell in the house. Additionally, you’ll probably develop health problems such as asthma and other lung conditions from breathing in fungal spores.
What percentage of damp is acceptable?
It’s generally accepted that any reading above 16% is considered damp. However, you’ll only know for certain by using a calibrated damp meter. Ask a specialist damp surveyor to check for damp if you have any concerns.
Find Damp Specialists In Your Area
Damp is one thing that you should treat as soon as it appears in your home. You can treat some types of damp yourself quite easily. But, if you can’t seem to find the root cause or if it’s a very serious case, contact a professional to sort it out. Even though the initial cost of damp proofing might seem a lot, it’s better to have it fixed than suffer major problems in your home. So, complete the form on this page and you’ll receive 2 to 3 quotes from suitably qualified professionals in your area.
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