How long does it take to install a Damp Proof Course?

The nature of the job determines the total time it will take to install a damp proof course. For instance, whereas a smaller job may require around 1-2 days to complete a bigger job may need up to a week.

On average, a full damp proof course on 3-bed semi should take around 3-4 days.


It is the process of making floors and walls impervious to water molecules, rising from the ground. Damp proofing is known to protect a building from both timber and structural decay. It is a long-term solution to keeping the interior part of a building free from water.

Usually, after a building is constructed, moisture eventually climbs up the walls through capillarity and then enters the interior part of a building. You may then notice damp spots on your walls & floors, peeling off paint, white powder like staff or brownish staining your walls. These are all indicators of a missing or ineffective damp proof course. It is especially common in buildings with basements.

If you are familiar with such signs and would like expert advice on how to go about it, feel free to get in touch with us.


What types of Barriers are used?

There are various types of barriers used to damp proof floors and walls such as damp proof course, damp proof membrane, integral damp proofing, cavity construction, pressure grouting and surface coating.

The two most common methods are:

a. Damp Proof Membrane(DPM)
Over the years dump proof membranes have taken to many forms including the use of asphalt, bituminous coatings, cementitious coatings, resin coatings sheet membranes and cavity membranes.

b. Damp Proof Course(DPC)
Use of damp proof course is considered an alternative to DPM. It includes the use of water repellants, osmotic and pore blocking. These methods were improvised so as to waterproof already constructed buildings since it proved almost impossible to insert them with a physical DPM.

How are these installed?

Water Repellant
A chemical solvent that is in the form of a gel, liquid, paste or cream is used. It is injected into walls via drilled holes and eventually joins up to form an impermeable layer.

It is believed that water molecules rise up from the earth through matter by capillarity or osmosis. As they move electrical potential is developed between the matter and the earth.
The osmotic damp proof course was developed as a result of this theory. In this method, a titanium wire is run around the walls that need waterproofing.

*Initially, a copper wire was used but was soon replaced by titanium due to its highly corrosive properties.

The wire is then connected to the mains which supply it with electricity. Its earth rods short-circuits the electrical potential caused by water molecules rising up a wall stopping any further movement.

Pore Blocking
Cement is combined with water using a ratio of 1:3 to form a semi-liquid mixture which is then injected into a wall’s mortar using a reusable gun. With time, it chemically reacts to compounds that take up the pore spaces. This blocks moisture from rising up the wall.


Damp proofing injection is a cost-effective and proven way to tackle rising damp in a building. Damp proof injection is applicable in all types of masonry walls. A chemical cream solvent is injected into the walls and floors and deeply penetrates the mortar creating a waterproof membrane.

Preparing to Inject Damp Proofing Cream

First and foremost, acquire and wear protective gear. A pair of gloves, gas mask and safety goggles will do.

Preparing to inject damp proofing cream involves:

Step 1 – Consultation
It is advisable to consult a professional to help determine how far moisture content has gone up the wall. This will establish the levels in which it is appropriate to remove plaster.

Step 2- Removing Plaster and Skirting Boards
Plaster and skirting boards are removed to recommended heights. If a qualified person is not available, it is considered safe to get rid of the plaster to a height of 1.5m since water normally rises up to a height of 1.2m.

Step 3- Drilling Holes
Drill holes into the mortar joint (avoid the brick and stones) using a 12mm diameter drill no less than 100mm apart. The holes should be drilled 10-20mm in depth in a continuous line.

Step 4 – Injecting With Chemical
Inject a dry zone injection fluid into the holes under low pressure using a hand pump or gun. Leave it to settle. Given time, the cream will chemically react to form a fundamental layer that prevents water molecules from penetrating the wall.

Note: Injecting with the chemical is considered most effective for newly constructed walls. Additionally, It is advisable to ensure only quality dry zone injection fluid is used for great results.


Penetrating damp is often referred to as rain penetration. It is the infiltration of moisture into the external wall of a building which later manifests itself as a stain of dampness enlarging in proportion after a heavy downpour. This is usually common in older buildings. A cavity wall that is constructed as per the required standards should channel infiltrating water back outside.

Symptoms of Penetrating Damp

For External walls
Brickworks is damaged- This often occurs when water which has penetrated a brickwork freezes causing cracking in the brick that later becomes a weak point in the wall structure.

The growth of moss on the exterior side of the wall- The perfect breading environment for moss and algae is a moist place. A damp wall hence creates a perfect living space for moss encouraging its broad spread on walls. This creates an unattractive appearance to the walls.

The stain of dampness on walls- Stains of dampness on external walls form and their sizes increase when more moisture penetrates into the wall.

For Internal Walls

Plaster damage- Paint and plaster peeling off and discolouration on the wall’s surface is as a result of dampness on the inner side of the wall.

Wooden fixture rotting- Wood rot is basically decay of wooden fixture by a fungus which digests moist wood. Excessive presence of moist in wood causes rot and decay in timber.

The growth of mould on walls- Moisture constantly present on an exterior wall may cause rapid growth of mould and its spread along the wall.

Causes of Penetrating Damp

Faulty building material
Penetration of rainwater may be caused by faulty building material. These are unmaintained gutters with clogged up downpipes and a poorly designed drainage that leaves water stagnant on one part of the floor or roof.

Ageing of building material.
All building materials have a definite lifespan. Weather conditions may affect the building materials and accelerate the rate of ageing. For instance, when water penetrates in a brick and is frozen, cracks are formed enabling water to infiltrate through the cracks created.


The first step is to establish the main cause and fix it. Check all possible leading causes e.g. Gutter, downpipes etc. confirm that all downpipes are in good order and unclogged to allow a smooth flow of water.

Using water seals on the external wall is preferable as this will prevent penetration of water which may cause damping.

Waterproofing your Exterior Brick Walls

External walls are constantly exposed to water sources including rainwater and snow hence a need to waterproof them.

The following are steps to waterproofing exterior walls

  1. Identify faults on walls and other building materials- Check to eliminate all other causes of structural dampness on the wall. Fix the issue and as a precautionary measure waterproof it.
  2. Choose the most preferable waterproof material. These waterproof products include: Concrete waterproofing, Silicate-based concrete sealer and Waterproofing paint.
  3. Prepare the wall to apply a waterproofing-Apply good-quality fillers to repair cracks on the wall to create an even surface so as to ensure good glueing between the substrate and waterproof material.
  4. Apply waterproof material- Either roller or a brush is used to apply. After applying the waterproof ensure that it fully dries before any interference.
  5. Assess the product effectiveness- Carry out an assessment to identify if the product meets the required expectations.


Moist air coming into contact with a colder surface like a wall, window, the mirror is known as condensation. Condensation occurs mostly in corners of rooms and behind furniture. Avoid this by good ventilation of a room.

Penetrating Damp
moisture coming into the house through leaking or cracked pipework, a damaged roof, blocked guttering is penetrated damp. The types of material may influence the likelihood to endure from water entering.

Rising damp
Rising damp is a type of damp that affects the wall of a building. Rising damp occurs when moisture from the ground is absorbed through small tubes and travels horizontally through the wall and if not corrected creates the right conditions for moss and mould growth on walls and peeling of paint.

During construction of a building, a damp proof course is installed at the lower levels of the wall which prevents water absorption. However, the damp proof course effectiveness decreases as the building gets older.

What are the Internal Damp Proofing Options?

Damp proof membranes
It is an impermeable layer polyethene of greater density that is subdivided and attached under the slab and wall to avoid dampness in the inner part of the building. Comes in different sizes with a thickness of between 0.5-1mm.

Damp proof paint
It’s a type of harmless product that minimises the risk of dampness in walls commonly referred to as water-resistant paint. The paint contains a highly powerful polymer that prevents water through the masonry wall hence protecting the wall from damping. The paint mostly is applied to the painted area of the walls and beneath the tile area acting as a secondary protection for wet areas such as kitchen and bathroom.

Cementitious tanking
It is a traditional way of waterproofing. Commonly used in underground wall, cementitious is a microporous cement base coating assisting in restraining water from passing through the wall by enhancing the cement bond.

Liquid epoxy damp proof membranes
Base and hardener are the two components in a liquid epoxy damp proof membrane. It normally used above the ground damp proof membrane on concrete floor and screeds

Anti-mould paint
The reappearance of mould on the wall can be prevented by use of an anti-mould paint. Durable and works as a water resistant on walls thus making it ideal for walls and ceiling in buildings.


To calculate the total cost you are likely to incur you need to put into consideration the amount of labour involved, manpower needed and taxes. It will also depend on whether a house is terraced, semi-detached or detached. Damp proofing a detached house is more expensive compared to a terraced one.

What do I Need to Install a Damp Proof Course?

You will need
• Protective gear- A pair of hand gloves, safety goggles, and face mask
• A damp proof course specialist
• Equipment and tools such as chisels, hand drills and a low pressure injecting gun.
• Quick Cure DPC Cream
• Skeleton gun (400cc or 1000cc)
• Electric hammer drill with 12mm masonry drill bit
• Re-plastering additives/materials
• Wall plugs

How much Does a Damp Proof Course Cost?

To determine how much a damp proof will cost you should consider the total size of the building and how thick its wall measure. If it is an uphill task to come up with this data, you can always hire a professional to help you out.

Here is a guide for how much DPC chemical you will require to damp proof a wall:

  • 4.5” thick single wall: 1 litre for every 9m from one side
  • 9” think cavity or double solid: 1 litre for every 4.5m from one or both
  • 8” thick filled or solid wall: 1 litre for every 2m from both sides

Damp treatment cartridges (310ml) can be purchased for around £20 each but you may be able to get 5 for under £100.

For larger projects and thicker walls, you can get 600ml cartridges for around £35 each or 3 for under £100.


Damp and mould cause respiratory problems, respiratory infections, allergies, asthma an affect the immune system.


Some people are more sensitive than others, including:

  • elderly people
  • babies and children
  • those with existing skin problems, such as eczema
  • those with a weakened immune system
  • those with respiratory problems, such as allergies and asthma


Moulds produce allergens that cause allergic reactions, irritants and sometimes, toxic substances. Inhaling or touching mould spores may cause sneezing, a runny nose, red eyes, skin rash and asthma attacks.


Excess moisture in buildings caused by leaking pipes, rising damp in basements and ground floors, and rain seepage through damaged windows and roofs.

Water still drying out in newly built buildings for example in plaster on walls.
Condensation also causes excessive moisture.

It is necessary to find out the reasons for excess moisture in your home to ensure you do the house repairs and take steps to limit condensation in the air. Ask for professional help to remove mould if in large amounts. Exposure to damp and mould may have severe reactions. Some people are more sensitive thus may undergo nasal stuffiness, throat irritation, coughing or wheezing, eye irritation or skin irritation.

People with allergies, weak immune systems and those with chronic lung illnesses may have more severe reactions and should stay away from mould infested areas such as; compost piles, cut grass and wooded areas.


Mould accumulates in damp and poorly ventilated buildings. Inhaling the spores or their fragments may inflame airways causing nasal congestion, wheezing, chest tightness, coughing and throat infections. Prolonged exposure to high levels of indoor dampness can reduce lung function and cause chronic health problems such as asthma. Those with asthma and allergies are more likely to have more severe symptoms when exposed.


Black mould, Stachybotrys chartarum, is the most infamous type of fungus which can grow on water-damaged building materials and produce toxic spores. In 1994, it was linked to a severe respiratory illness after ten children experienced idiopathic pulmonary haemosiderosis and one subsequently died. There was no causal link despite significant media interest.

Mould is found both indoor and outdoor. It can enter your home through open doorways, windows, vents, heating air conditioning systems, and by attaching to clothing, shoes, bags and pets,Mould grows well on paper product’s, cardboard, ceiling tiles, wood products, in dust, paints, wallpaper, insulation, drywall, carpet, fabric and upholstery. Mould can be removed from hard surfaces using commercial products, soap and water, or with a bleach solution of no more than 1 cup of laundry bleach in 1 gallon of water.

Mould growth often looks like spots, with many different colours and smells musty. Effects of mould on people vary greatly, and once you see or sniff a fungus, remove it. Good sampling for decay is expensive, and the standard for accepting the appropriate quantity is not yet set, hence not recommended by the CDC.


Damp has become a big problem for many with the average home subject to a lot of rainwater with the high rainfall in the United Kingdom. Damp is unsightly with a bad smell, can cause permanent damage to plaster, paint and finishes, is terrible for our health, aggravating respiratory problems and encouraging the emergence of mites and mould.

Before damp proofing, determine the causes. The traditional moist wall treatment was to cover up with wooden panelling but this tends to dampen over time and rot.

The dry lining evolved into the air gap membrane, damp proof membrane or cavity drain membrane; which is a dimpled plastic sheet which allows air to circulate and flow freely and thus prevents moisture from becoming trapped which can drive dampness sideways and upwards and into other areas of your home and cause further damp and mould problems.

Damp proof membranes are made from high density, impervious polyethylene (HDPE). Fix the films to internal walls after the source of the damp has been resolved. The surface has an egg box-like profile that creates a cavity or an air gap that allows moisture to evaporate from the wall behind. The membranes are easy to install and are extremely flexible; which means that they can cope with movement thus ensures that your damp proofing lasts for decades.


Water and moisture that is allowed to pass through a wall onto its inner surface will maintain a colder temperature than its surroundings and can cause condensation to build up and black mould growth.

When moisture passes it carries salts and minerals with it, which reach the inner decorated surface that is usually covered with plaster or paint ruining it and eventually blowing the plaster off the wall.

Wall surface below damp proof course will always remain damp since its surroundings naturally contain water and moisture.

The traditional method of dealing with this was to batten the inner wall surface out, and panel over the top of it which would be ok for a while till the wooden tablet would become damp and rot.

Technology has advanced and given birth to tanking; which is effectively a liquid coating that bonds to damp masonry and then cures to form a waterproof barrier.


The three principal methods of tanking wet walls include;

Liquid bitumen coating –

Paint the liquid bitumen coating onto the cleaned brickwork, stone, block or render, which is difficult to apply to old damp salt masonry, is prone to separation from the wall and render coats due to incomplete curing and is best for non-critical small jobs or external coating below the damp proof course.

Cement based slurry –

Apply the cement-based slurry by soft brush onto dampened, cleaned brickwork, stone, block or render, which is easier to use because the cement base wants to amalgamate with the masonry and mortar. It is not a vapour barrier so needs to be finished with breathing materials. It is ideal for partial below ground situations or exterior coating on foundation walls.

Air gap membranes –

Air gap membranes are not strictly tanking in the same way as liquids. It is a dimple plastic sheet fixed onto brick, stone, block or render with plastic plugs to form an air gap cavity. These membranes can have a common surface for battening or a mesh surface for direct plastering or plaster boarding. It is ideal for cold, single leaf walls and lining rooms with cold solid 9 inch walls.


As an example project, what is the cost of a chemical injection into the external walls of a 2-bed house in Surrey?

Example 1.
A professional injects a damp proofing chemical liquid into the external walls. This job does not include internal plastering or finishing off work.

  • Small Business £1100.00
  • Larger Business (5+ employees) £2000.00

Example 2.
First the damp proof engineer will remove the extensive damp patches of plaster from internal walls up to a height of 1.5 meters; the chemical is injected into external walls; the walls will then be sealed and replastered.

  • Small business £3250.00
  • Larger business (5+ employees) £4750.00


The plastering and making good of the walls is time consuming unlike wall injection.

Damp proofing is a messy and disruptive project that will require e you to move out of the house for a few days. You might be tempted to paint the interior walls with waterproof paint or sealant to mask signs of damp, if on a tight budget.

It may seem logical and practical but is a bad idea. The damp will spread behind the sealant if moisture is still present and resolve the underlying issues which can lead to further horizontal or vertical damage, the plaster, bricks, floor joists and may fail as it never has the chance to dry out, and damp odours and smells will persist.

Walls should only be coated with a waterproof sealant if 100% sure that there is no damp rising from the ground below to avoid masking the issue by sealing the moisture into o the wall where it will spread and damage the materials used in the construction of the wall.


Cellars are often damp and unstable beyond storing the odd bottle of wine and old tin of paint. If you want to make full use of your cellar or basement then you will need to keep it dry, tanking systems provide an impermeable waterproofing coating to the walls and floors to help keep the basement dry.

When it comes to water-proofing a basement with damp walls, there are two main options;

One, is to install a cavity drain system, or use cellar tanking. Cellar tanking refers to above the damp ground proofing as well as cavity wall membranes as part of a basement drainage system.

Cellar tanking or basement tanking refers to the application of a liquid waterproof coating to the walls and floor of a cellar. It is used to treat damp walls by preventing water ingress, effectively making the walls permanently water-tight.

Damp walls are common in cellars as the walls are below ground. Water from the retaining earth can make its way through the walls and into the cellar moisture passes through the wall carrying salts and minerals with it.

Damp walls are cold which create s issues with condensation and in turn mould. The tanking slurry is designed to deal with these issues. It is applied directly to damp walls. When the tanking slurry cures, it forms an impermeable waterproof barrier thus preventing water ingress and damp.

It is important to point out that unlike a cavity drain system, taking slurry blocks water from entering your cellar rather than allowing it in and controlling it to an evacuation point.


The cost of tanking a cellar depends on the size of your basement, the type of substrate and the extent of the damp. Most tanking costs will be calculated on a meter squared basis and be an estimated range.

For example, PermaSEAL tanking slurry comes in 25kg buckets; this will cover between 8m2 to 12m2 unit depending on the substrate.

The grey slurry is currently available at £31.00 excluding VAT.

If we take the lowest coverage estimate of 8m2 per bucket, then the cost of cellar tanking works out at £7.75 per m2 for two coats.

Now, if you have four walls at 2metres high and 8 metres long then, this would come in at 16 buckets for £496.00 ex VAT for the wall with the floor being a further 16 buckets at £496.00 ex VAT.