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Using Damp Proofing Injection Cream to Treat Rising Damp

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Rising damp can be a very serious issue for homeowners. Thankfully, technology has advanced and high-strength damp proofing creams have been developed to effectively stop rising damp. When installed correctly, injection damp proof courses provide a long-term and reliable solution to the horrors of rising damp. 

What is Rising Damp?

Rising damp occurs when ground water moves up a wall through small tubes in the bricks by capillary action (like a straw sucking up water). Most walls allow some water in, but it’s usually stopped from causing damage by a barrier called a damp proof course (DPC). If you don’t have a DPC or it has failed then there is nothing to stop water rising up your wall. Rising damp can also occur when the ground level outside your home is higher than your damp-proof course, allowing water to bridge the damp proof course.

It is vitally important to know for certain that you have rising damp. It is a relatively rare form of damp and treatment will only work if correctly diagnosed. It is always best to consult a professional. To find out more about Rising Damp and how to identify it then read our Damp Guide . Once rising damp has been diagnosed you can then look at your options for treating it.

How to Treat Rising Damp Using Damp Proofing Cream

By far the quickest, most economical and effective method to treat rising damp is to use a high strength damp proofing cream. This cream is injected into holes drilled in the mortar joint. It then penetrates the masonry to provide a water repellent barrier.  You are now able to relax safe in the knowledge that you have a high performance chemical damp proof course installed and that your home is protected from rising damp. Another benefit is that the damp proof injection method can be used in walls that are highly saturated with water. 

How Do Damp Proofing Creams Work?

Damp proof creams are scientifically formulated to penetrate deep inside the building material. They have a consistency that allows the active ingredient, silane, to be absorbed into the substrate both vertically and horizontally without running out. The silane then lines the capillaries before curing to create a water repellent barrier. 

How to Inject Damp Proofing Cream  

Preparing to inject damp proofing cream.

You will need to prepare both internally and externally before injecting your damp proofing cream. Start by removing any skirting boards, architraves, as well as disconnecting any radiators. You will want to expose the brickwork to the required level before starting injecting the DPC.

If you are suffering from rising damp then damp will have left tidemarks and other visible damp damage on the plaster. It is important to remove this contaminated plaster before injecting a DPC. Hack off the plaster to a height of no less than a metre.

In some rare instances, depending on the conditions, the water may have been wicked up higher than one metre so you should consider removing plaster at least 300mm above the highest visible sign of damp/ hydroscopic salts. It’s also worth pointing out that rising damp will not necessarily rise uniformly to the same level across all parts of a wall so adjust the amount of plaster to be removed accordingly without ever slipping below one metre.

You are now ready to inject the Damp Proofing Cream:

Injecting Damp Proofing Cream

1.  Drill 12mm diameter holes horizontally into the mortar joint 150mm above ground level - if this is not possible then flanking works must be introduced to stop bridging of the damp proof course. Always drill with a 12mm drill bit to a depth of 10 - 20mm from the opposite face and at 120mm centres, never more. Do not drill into the bricks or stone and always follow the mortar joint in one continuous line.

2. Inject the cream into the boreholes using a low pressure sprayer or cartridge gun.

3. Leave the cream to revert to its liquid phase and penetrate the masonry surrounding the hole.  4. The silane then lines the capillaries in the substrate to create a water repellent barrier. 

DPC Creams can take up to 6 weeks to fully cure and create a new damp proof course.

Making Good

Injecting a Damp Proof Cream is only the first step. You will need to re-plaster internally. It is recommended that you delay the re-plastering works for as long as is feasible to facilitate the maximum possible period for drying. However, this is not always possible so products like the damp proof membrane kit and PermaSEAL tanking can be used for early re-plastering.

Re-rendering should always be to a specific re-rendering specification to stop salts from transferring into the new plaster. See our Guide to Internal Waterproofing for more information. Externally, you should make good the boreholes with sand and cement.

How Not To Inject Damp Proof Cream

There are errors that you need to avoid when injecting a damp proof cream.

• Drill directly into the brick or into stone – drill into the mortar line in a continuous line 
• Apply into pre-existing holes that someone else has drilled
• Inject a DPC when there is an existing effective DPC like Edwardian blue engineering bricks
• Inject if the mortar joint is of poor quality or crumbly. In this instance you will need to repair the joint and allow to fully cure before drilling and injecting the cream.
• Inject when there is a bridged cavity walls. Over time cavity walls fill up with debris and this can bridge the DPC. Moisture can then pass across and cause damage. If you inject a DPC in these circumstances it will not work.

DPC should be installed to BS 6576:2005, “Code of practice for diagnosis of rising damp in walls of buildings and installation of chemical damp-proof courses.”

Gallery of Shame

DO NOT DRILL OR INJECT INTO STONE OR UNKNOWN SUBSTRATES

The installation in the above photograph should have either taken place from the inside into a visible mortar joint or the external render should have been removed to find a mortar joint 150mm above ground level.

SPACING SHOULD BE EVERY 120MM (APPROX HALF A BRICK)

Measure out 120mm spacings which should co-inside with every half a brick. 

THE INSTALLATION SPACINGS AND HOLE SIZE IS CORRECT IN THE BELOW HOWEVER IT IS INSTALLED ON A PLINTH WHICH WILL DIRECT WATER INTO THE UNFILLED HOLES AND ALSO LEAD TO SPLASHES BRIDGING THE NEW DAMP PROOF COURSE

The injection should have been installed at a higher level and the plinth should have been angled to direct water away from the wall. Also, a coat of Microshield Ultra should be applied to protect from penetrating damp.

The Best Damp Proofing Cream

At Permagard, we've developed a professional DPC injection cream with the highest possible concentration of active ingredients. It is a market-leading solution that we're very proud of. 

PermaSEAL PRO DPC Injection Cream

PermaSEAL PRO DPC Injection Cream , also available as a 10 cartridge PermaSEAL PRO DPC Injection Kit , provides permanent protection against rising damp. This high strength cream is specially formulated to allow you to efficiently create a new DPC in walls of various types, including substrates saturated with water.

How Do I Know Damp Proof Creams Works?

High strength Damp Proof Creams have been used widely across the UK and Europe for over 25 years. Based on proven technology, they are the most reliable and efficient way to treat rising damp. 

For more information on damp proofing cream or any other of our  damp proofing products  including physical damp proof courses , search our website or contact us on 0117 9823282. 

Chris is a Certificated Surveyor in Structural Waterproofing and the Technical Manager at Permagard. With a background in the communication sector, Chris has made it his mission at Permagard to provide each and every customer with the information they need to get the job done. 

Whether on the technical helpline, behind the trade counter or with our How To guides, Chris makes sure that our users feel complete confidence in the systems and products we sell, and know how to use them to get the job done. If you’ve got a question about any of our systems or products, Chris will be more than happy to help.

View  Chris's full profile  or connect with him on  LinkedIn .

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Home > DIY How To Projects and Tutorial Guides > DIY Damp Proof Injection: How to Install a Damp Proof Course

DIY Damp Proof Injection: How to Install a Damp Proof Course

DIY damp proof injection. How to install a damp proof course and advice on repairs to damp proofing if your damp course has failed. Damp proofing advice and recommended DPC products including Vertical DPC and the injection technique using cream DPC.

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A damp proof course (DPC) is a physical barrier inserted into the fabric of a building to stop water passing from one place to another. This can be on a horizontal plane, stopping water rising up from the ground by being sucked up by the dry masonry above, or vertically to stop water passing from the outside of a building, though the masonry, to the inside.

DPC’s have taken many forms through the ages and one of the earliest forms was to use a layer of slate in the construction. Slate is still used but the less expensive plastic version is now more widely used.

In some instances a DPC can fail and cause water and moisture to creep up through a wall, causing untold damp issues. In this guide you will find out about damp proof injection and how to install a damp proof course yourself.

Damp Proof Course indicating DPC and ground level

Damp Proof Course

Damp Proof Course indicating 6 inches from damp proof course to ground level

A horizontal damp proof course is usually placed 6 inches above ground level and used in conjunction with a damp proof membrane which stops water rising to any part of the ground floor from the ground.

A diagram of a typical ground floor construction can be seen below and you can see how a Damp Proof Course works in conjunction with the membrane to stop any water rising up into the building above.

Damp Proof Course Cross Section indicating ground floor slab and inner and outer cavity wall DPC’s

In many older properties a non porous stone was used to build the first few courses of masonry but over the years this stone in many instances has become porous allowing water to be soaked up through it.

It is not practical in most cases to remove a course of stone to place a plastic, lead or slate DPC in the wall and new methods have been found of introducing a DPC (damp proof course) where there is either none, or one that is broken in some way.

These methods generally require the injection of chemicals into the walls and, on a larger scale, are better done by specialists as there are many complications which can arise as a result of saturated plaster and the measurement of the chemical being injected.

DPC Injection made easy with modern techniques and drilling templates – Image courtesy of Property Repair Systems

Modern DPC Injection Cream – no special tools, no smell and can be installed by anyone

Now you can make repairs or add a DPC to small projects using a unique DIY method involving simple injection of a specialised cream using a normal sealant applicator gun after drilling 12mm holes to inject into!

DIY Damp Proofing – An Easy Solution for Damp Proof Courses

At last it is practical for home and amateur users to insert a chemical damp proof course reliably, even in thick stone walls. This is because ‘damp proof course injection creams’ are now available and have taken over from the high pressure injection of liquid.

The old injection technique was hit and miss – even the ‘professionals’ struggled with blow backs, loss of fluid via fissures and the difficulty of getting a seal in crumbling masonry.

Your only option then, as a private property owner, was to pay for a damp proofing company to carry out the work, including the inevitable expensive replastering. Now you can even obtain your own Product Guarantee Certificate after injecting your own damp proof course.

The new generation of DPC injection creams have appeared and for the first time private individuals and developers, builders and DIY enthusiasts can reliably and cheaply inject their own chemical DPC and prevent damp issues.

Small jobs are no problem – the cream arrives in clean, sealed plastic, disposable cartridges, ready to fit into a standard skeleton gun. Nothing could be easier to inject. Simply drill the hole, blow out the dust and inject. It takes about 1 – 2 minutes per hole and anyone can do it!

DPC injection cream cartridge with skeleton gun

Information and Main Features of DPC Injection Cream

• Quick and easy to install – drill the holes, blow out the dust, inject. No special tools required
• No wastage – Comes in a standard ‘mastic’ tube, ready to use and fits straight into your skeleton gun
• Low hazard – not even rated as irritant
• Spillage and mess eliminated – no liquids to spill or stain
• No electric DPC pump required – No electric pumps to hire or messy, smelly fluids just simple hand pressure only
• DIY technology – advanced emulsion uses active Silicone ingredient economically (Siloxane and Silane, for the technically minded) without running back out of the holes

Typical Usage Rates for Most DPC Injection Creams

The following information states typical usage rates for most DPC creams, however for accurate usage rates refer to the manufacturers guidelines for your particular product.

• 4.5 inch thick (115mm) single leaf wall – 1000cc (1 litre) per 9 metres, inject from either side
• 9 inch thick wall (230mm) double leaf solid or cavity – 1000cc(1 litre) per 4.5 metres, inject from one side or from both sides.
• 18 inch thick wall (460mm) solid or random fill – 1000cc (1 litre) per 2 metres, inject from both sides

DPC cream injection being injected as a damp proof course to a property – Image courtesy of Property Repair Systems

How to Install a Damp Proof Course

First, check for high ground levels, leaking gutters and down pipes and any other water leaks. These should be fixed prior to any DPC injection taking place.

• Drill 12mm diameter holes at 115mm intervals in the mortar course (or via the brickwork, angled down to meet the mortar course) selected to be at least 150mm above outside or abutting ground level
• Fit the extension nozzle to the cartridge tube and load into the skeleton gun
• Inject cream from the bottom of the hole outwards until the hole is full.
• Holes can be capped with mortar or fitted with a plastic plug

Plastic tapered plugs for filling drill holes after injecting DPC cream

Walls and Skirting Board

Don’t forget to check the walls and skirting boards for dampness. Typically the best way to check for damp is to use a “damp meter”. These handy tools measure the moisture content in a given object or surface.

If any damp is found it will need to be dried after you have resolved any damp proof course issues and laid a new cream DPC. Once dried any damaged skirting, architrave or other timber will need to be replaced.

In the case of any damp plster, replaster to a minimum of 1.2 metres internally. It’s a good idea to also include additives such as salt neutralisers in with the plaster mix as this will prevent ‘salts’ damage to plaster finishes and decorations.

Replastering concentrated additive for renders to prevent salt growth – Image courtesy of Property Repair Systems

Replastering is an essential job after inserting a chemical damp proof course. For more information on how to do this correctly see our replastering project for detailed information.

In some cases you are better off using an Air Gap Membrane instead of sand and cement – Information and advice on these membranes and how to use them can be found here .

Air gap membrane can be used in place of plaster and is simply fixed with plastic plugs

What Depth Should Chemical Damp Proof be Injected?

The depth that the chemical damp proof should be injected is dependent on the thickness of the wall. Use these suggested injection depths as a guide and drill the holes to the following depths:

• For 115 mm walls (half brick thick) the holes should be 100mm deep
• 230mm walls (1 brick thick) the holes should be 210mm deep
• 345mm wall should have 320mm deep holes
• 460mm walls should have 430mm deep holes

The DPC cream that you use will have detailed instructions which you should follow. These should include information about the depth to which the chemical damp proof should be injected, but if not the above guidelines will suffice.

What is Needed to Inject a Damp Proof Course

Products and tools required.

• DPC injection cream – There are quite a few available on the market today, a simple online search will reveal a selection. Some of the best are generally Permaguard, Dryzone and teh similar
• Skeleton Gun – either a 400cc or professional 1000cc
• 12mm masonry bit
• electric hammer drill
• eye protection

Injecting a damp proof course can seem like a daunting job if you have never tackled such a task before but many products come with detailed instruction and many manufacturers also include warranties and guarantees with their products.

Alternatively if you would like to know a little bit more about what’s involved with the whole process, see our damp proof injection and how it works project here .

All project content written and produced by Mike Edwards , founder of DIY Doctor and industry expert in building technology .

Apologies, but we don't seem to have a video for this project yet, but we will do our best to get one up soon

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Related Projects That May Help You:

• Building Regulations Approved Document C
• Fixing Damp Issues Below a Damp Proof Course
• Cavity Wall Damp: Diagnosing and Fixing
• Damp Proof Injection and How it Works

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What is Damp Proofing, and How Does it Work?

When it comes to acquainting yourself with different aspects of damp and its treatments, one of the first terms you may encounter is “damp proofing.” To protect your home from the causes of rising damp and penetrating damp, including seasonal damp problems, a suitable damp proof course (DPC) must be in place. A DPC is one of the most imperative features of a property, as it inhibits moisture from rising from the ground.

Damp issues when selling/buying a property can be detrimental to the home’s value. Excess moisture in a property can affect the plaster and decoration and can even lead to woodworm, and wet or dry rot in timber. The way damp affects your property’s valuation is just one of the potential problems; damp can also harm your home’s structural integrity.

Due to the severity of the impact that damp can have, most properties have a DPC installed. Despite this, dampness in historic buildings can pose a real risk, as DPCs were not common practice until 1875. Therefore, if your house is around 150 years old, and your DPC hasn’t been renewed any time recently, it could be susceptible to damp problems.

Different Types of Remedial Damp Proof Courses

There are three main types of remedial damp proof course, and the construction of your property will determine which is most suitable for your home.

The first is a damp proof course injection, describing a liquid or cream injected into the wall. This acts as a water-repelling layer, which inhibits damp from rising above the DPC, and is often referred to as a chemical damp proof course injection. The process involves drilling holes into the wall at least 150 mm above external ground level and filled with the water-repelling cream.

Next up is a mortar injection damp proof course, which bears similarity to the damp proof course injection, as it’s also injected into the wall. Despite this, a chemical-enhanced mortar is used instead of liquids or creams. This is the most appropriate course of action when the property is constructed from rubble, resulting in structural gaps.

Last but not least is an electro osmotic damp proof course, which is employed when chemical use isn’t appropriate or approved. This involves the use of titanium and copper wiring, which provides the wall with a minor electric charge. Consequently, the polarity of the capillarity is reversed, and the rising damp is pulled below the DPC.

Do All Properties Have a Damp Proof Course?

As previously mentioned, DPCs became compulsory in 1875; however, this doesn’t necessarily mean that all structures built after this year are covered. As you can imagine, DPC technology has come a long way in the last 147 years. The original DPCs laid after 1875 may no longer serve their intended purpose.

Originally, lead, or slate barriers were fitted into the walls to create a DPC. Since then, DPCs evolved to include bitumen felt and eventually plastic. As a result, old DPCs may fall victim to bridging, damage, and deterioration, meaning that a new DPC may be required.

Upon noticing signs of rising damp, some homeowners invest in damp-proof paint and deem this an effective DPC. Despite this, damp-proof paint won’t provide your property with the protection it needs against rising damp. Instead, it may only temporarily mask the problem and perhaps offer you a short-term solution, but for complete protection, you need a suitable DPC.

What Causes Damp Walls

In order to solve your property’s damp issue, you must first identify where the moisture is coming from. Garratt’s Damp & Timber Ltd offers a free site survey, in which we can inspect your property in its entirety to identify the source of damp problems.

Some of the most common causes of damp issues include:

• External flooding
• Faulty drains
• Plumbing leaks
• Insufficient door and window pointing
• Faulty cavity wall insulation
• Condensation problems
• Defective exterior masonry or render
• Faulty downpipes, gutters, or roof coverings
• Ground levels that have historically increased and bridged the physical DPC

If you believe that your home is suffering from damp, it’s vital that you get the diagnosis confirmed by a professional. Without this specialist confirmation, you may end up paying for unnecessary remedial work.

How to Identify Damp Walls

When identifying damp walls, inspect your property’s interior and exterior for any defects. If you notice any signs of damp, you might use a moisture meter, which can inform you whether your home’s moisture content is above average. Following this, you should always get in touch with a damp and timber specialist to assess and diagnose the issue.

Damp Proofing Cost

Unfortunately, it’s difficult to say how much damp proofing costs, as every property is unique and will have a different set of requirements.

If you’re concerned about damp in your property, be sure to have your home surveyed by a professional. Get in touch with Garratt’s Damp & Timber Ltd. to arrange your free site survey and obtain a quote for any required work.

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Damp proof course (dpc) -methods of dpc installation in construction [pdf].

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What is DPC?

The damp proof course (DPC) is generally applied at basement levels, which restricts the movement of moisture through walls and floors. The selection of materials for the damp proof course and its various methods of applications in buildings is discussed.

Materials for Damp Proof Course (DPC)

Properties of materials for dpc.

An effective damp proofing material should have the following properties;

• It should be impervious.
• It should be strong and durable and should be capable of withstanding both dead as well as live loads without damage.
• It should be dimensionally stable.
• It should be free from deliquescent salts like sulfates, chlorides, and nitrates.

Types of Materials for Damp Proof Course

The materials commonly used to check dampness can be divided into the following three categories:

• Flexible Materials: Materials like bitumen felts (which may be hessian based or fiber/glass fiber-based), plastic sheeting (polythene sheets), etc.
• Semi-rigid Materials: Materials like mastic, asphalt, or a combination of materials or layers.
• Rigid Materials: Materials like first-class bricks, stones, slate, cement concrete, etc.

Selection of Materials for Damp Proof Course in Buildings

The choice of material to function as an effective damp proof course requires a judicious selection. It depends upon the climate and atmospheric conditions, nature of the structure, and the situation where DPC is to be provided.

The points to be kept in view while making selection of DPC materials are briefly discussed below:

1. DPC above ground level

For DPC above ground level with wall thickness generally not exceeding 40 cm, any one of the types of materials mentioned above may be used. Cement concrete is however, commonly adopted material for DPC at plinth level, 38 to 50mm thick layer of cement concrete M15 (1:2:4 mix) serves the purpose under normal conditions.

In the case of a damp and humid atmosphere, a richer mix of concrete should be used. The concrete is further made dense by adding waterproofing materials like Pudlo, Impermo, Waterlock, etc. in its ingredients during the process of mixing. It is used to apply two coats of hot bitumen over the third surface of the concrete DPC.

2. DPC Material for floors, roofs etc.

For greater wall thickness or where DPC is to be laid over large areas such as floors, roofs, etc., the choice is limited to flexible materials that provide a lesser number of joints like mastic, asphalt, bitumen felts, plastic sheets, etc.

The felts, when used, should be adequately bonded to the surface with bitumen and laid with joints properly lapped and sealed.

3. DPC Material for situations where differential thermal movements occur

In parapet walls and other such situations, materials like mastic, asphalt, bitumen felts, and metal (copper or lead) are recommended.

It is vital to ensure that the DPC material is flexible to avoid any damage or puncture of the material due to differential thermal movement between the material of the roof and the parapet.

4. DPC material for Cavity Walls

In cavity wall construction, like cavity over the door or window should be bridged by flexible material like bitumen felt, strips or lead, etc.

Methods of  Damp Proof Course Installation in Construction

The general principles to be observed while laying a damp proof cours e are:

• The DPC should cover the full thickness of the walls, excluding rendering.
• The mortar bed upon which the DPC is to be laid should be made level, even and free from projections. Uneven base is likely to cause damage to DPC.
• When a horizontal DPC is to be continued up a vertical face, a cement concrete fillet 75mm in radius should be provided at the junction before the treatment.
• Each DPC should be placed in correct relation to other DPC to ensure a complete and continuous barrier to the passage of water from floors, walls, or roof.

Figures 1 to 7 explain the provision of damp proof course under different conditions

The damp proof course (DPC) is generally applied at basement levels, which restricts the movement of moisture through walls and floors.

The abbreviation of DPC is the Damp Proof Course.

The desirable properties of DPC material are- A. It should be impervious. B. It should be strong and durable and should be capable of withstanding both dead as well as live loads without damage. C. It should be dimensionally stable. D. It should be free from deliquescent salts like sulfates, chlorides, and nitrates.

A. Flexible Materials : Materials like bitumen felts (which may be hessian based or fiber/glass fiber-based), plastic sheeting (polythene sheets), etc. B. Semi-rigid Materials : Materials like mastic, asphalt, or a combination of materials or layers. C. Rigid Materials : Materials like first-class bricks, stones, slate, cement concrete, etc.

Read More:  Materials for Damp Proof Course in Construction Works

Gopal Mishra

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The Ultimate Guide to Damp-Proof Course

If you’re looking to damp proof your home , a damp-proof course is an essential protective measure. A damp-proof course is designed to stop water from rising up into a home by creating an impermeable waterproof barrier, and it can protect your home from potentially expensive and dangerous issues that may result from damp.

Modern homes are fitted with a damp-proof course as standard , but older homes may not have ever had one installed. A damp-proof course can fail for any number of reasons, but a damp-proof specialist can help you to identify and fix problems before they can cause damage.

To help you understand the importance of damp proofing your home , the experts at Danford, Brewer & Ives have put together their ultimate guide to damp-proof courses.

What Is a Damp-Proof Course?

A damp-proof course is designed to protect a property against the dangers posed by moisture, damp and excess water. When properly installed, a damp-proof course creates an effective waterproof barrier that prevents moisture from rising up through the brickwork and masonry, and then into the home.

A damp-proof course is generally fitted just above ground level, with the main goal being to protect against rising damp. There are several different types of damp-proof courses that can be installed, with the most common method being to inject a damp-proof cream into the ground floor masonry.

Without a damp-proof course to create a waterproof barrier , excess groundwater and moisture can rise up through the brickwork and cause damage to a property. If left unchecked, this damp problem can lead to structural and health and safety issues within your home.

How Do Damp Proof-Courses Work?

All damp-proof courses are intended to create a protective barrier that stops water from rising from the ground and into the home, but there are different types of damp-proof course and they all work in slightly different ways.

Any damp-proof course needs to be installed at least 150mm above ground level. This is a legal requirement, and it ensures that the waterproof barrier is formed above groundwater level. Because a damp-proof course is intended to protect primarily against rising damp , which enters a building from the ground upwards, they are generally installed in the masonry or brickwork on the bottom floor of a home.

Modern damp-proof courses consist of chemical injections, but they are at their most effective when used in conjunction with other damp-proofing methods, such as a damp-proof membrane. Here are the most common varieties of damp-proof courses that can be installed in your home:

Chemical Damp-Proof Course

A chemical damp-proof course is injected into the masonry and brickwork of a home, and is at its most effective when placed 150mm above ground level. It consists of a specialist damp-proofing cream that forms an effective waterproof barrier once it’s settled into the brickwork.

To be installed, holes are drilled directly into the wall at the intended level, and the chemical damp-proof course is then injected into them.

Mortar Damp-Proof Course

A mortar damp-proof course is also injected directly into holes drilled into a wall, and again it must be injected 150mm above ground level for it to work effectively.

Mortar damp-proof courses consist of a chemically enhanced mortar that can fill any holes in the masonry and brickwork that might be causing damp problems.

The mortar, once injected, creates a waterproof barrier by filling in these holes and removing any chance of rising damp moving through the walls by removing any gaps in the brickwork.

Non-Chemical Damp-Proof Course

Non-chemical damp-proof courses are also available, with the most popular method being an Electro Osmotic damp-proof course. This works differently from a chemical damp-proof course because it involves installing metal wiring to create an electric charge.

Rather than creating a physical, waterproof barrier, this electric charge changes the polarity of the wall itself. This means that rising damp isn’t drawn upwards through the brickwork, but is repelled downwards.

This system isn’t as common, as it’s more difficult and time-consuming to install in comparison to a simpler chemical injection.

Damp-Proof Membrane

A damp-proof course creates an effective barrier against rising damp, but it works best when installed alongside other damp-proofing methods. The most popular damp-proofing method is a damp-proof membrane, which creates a physical impermeable barrier that protects against damp and moisture.

A damp-proof membrane is essentially a thick sheet of waterproof material that’s installed above or below the floor. A damp-proof membrane needs to be at least 1,200-gauge thickness and it needs to be installed so the sheets overlap, and therefore create a continuous barrier.

Why Do I Need a Damp-Proof Course in My Home?

The main goal of a damp-proof course is to protect against different forms of damp and water damage that could cause costly and even dangerous repairs. Damp is caused by excess moisture and water, and the damp-proof course exists to create a waterproof barrier against this.

Damp can cause any number of problems inside your home, including:

• Structural damage
• Decaying timbers
• Damaged plaster and decorating
• Wet and dry rot
• Respiratory illness

There are several types of damp that can be found inside a home, including condensation, rising damp and penetrating damp. A damp-proof course is primarily intended to protect against rising damp, which occurs when water rises up through the brickwork from ground level using capillary action to move vertically through bricks and mortar.

If rising damp is left unchecked, it can eventually cause serious structural damage to the foundations of your home. Other unwanted side effects include fungus and mould, which can lead to respiratory illnesses and serious health and safety dangers for anyone who lives in the house.

Lack of a damp-proof course is one cause of rising damp, although it can also result from major leaks, floods or other broken infrastructure, such as drains or pipes. For this reason, it’s important to ensure that your home is fully damp proofed, with an effective damp-proof course in place to protect against excess moisture and water.

How Do I Know If My Home Has a Damp-Proof Course?

Your home should already have some form of damp-proof course installed . Since the late 19 th century, it’s been a legal requirement for a property to have a damp-proof course installed. This means that modern homes will have one already in place, and it’s very likely that much older homes will, at some point, have had a damp-proof course installed too.

However, there is a small chance that a Victorian-era house may never have been upgraded with a modern damp-proof course . If this is the case, then it’s important to have a modern damp-proof course installed quickly and to have any other damp-proofing measures updated.

A damp-proof course is also liable to deteriorate over time, in which case you could find your home affected by damp problems. The ground may shift, walls may sink, or brickwork and masonry may crumble after the damp-proof course has been installed . Regular checks and a professional damp and timber survey can help to identify any existing issues with the damp-proof course in your home, or in a property you might be hoping to purchase.

If you are worried that your damp-proof course is failing, there are several key signs to look out for. The following are all big indicators that your home has a damp problem, which could be the result of a damaged damp-proof course:

• Damp, musty or mushroomy smells
• Mould and fungal growths
• Damp patches on the walls
• Damaged plasterboards or wallpaper
• Crumbling or damaged masonry or brickwork
• Tide marks on the walls
• Unusual growths on the outer walls

You can spot signs of damp on both internal and external walls, but the most noticeable sign of damp is likely to be a strong musty smell drifting through the home. If you spot salty tidemarks on the walls, this is a common sign of rising damp, which as we’ve explained, generally results from a failed damp-proof course.

Of course, a failed damp-proof course isn’t the only cause of damp, and different types of damp can result in different problems and require different fixes. If you are worried about any issues relating to damp, then it’s important to have a professional inspection in order to correctly identify the cause and solution of the problem.

How Do You Fix a Damp-Proof Course?

A broken damp-proof course can either be fixed or replaced entirely. If you notice any of the key signs of damp in your home, then the first stage is to call in a professional for a damp survey .

The professional will identify the cause of the damp and the type of damp before recommending the best way to fix the problem. If the issue is a broken or missing damp-proof course, then they will recommend the best type of damp-proof course to have installed.

Before the damp-proof course is fixed, any damp needs to be removed. Once this has been done, the new damp-proof course can either be injected or fixed in place. This may involve removing brickwork or timbers to gain access, or it could be as simple as drilling holes into the walls and injecting a chemical damp-proof course.

How Much Does a Damp-Proof Course Cost?

The cost of a damp-proof course varies from one home to the next, as multiple factors need to be considered and priced up. The main factors that affect the overall cost are:

• The size of the home
• The type of damp-proof course
• The amount of work needed
• Damage already caused by damp

Let’s take a look at the above factors in more detail:

The Size of the Home

Broadly speaking, the larger the property is, the more it will cost to have a damp-proof course installed. This breaks down to a higher cost for more supplies and materials, and more time needed to fix the damp-proof course in place.

The Type of Damp-Proof Course

Different types of damp-proof courses have different costs associated with them. The best value damp-proof course is a simple chemical injection, while a physical damp-proof membrane can cost comparatively more per square metre to be installed.

The Amount of Work Needed

The amount of time and work needed to properly install a damp-proof course also has a large effect on price. If your home is older, safe installation could be more difficult and this causes an increase in price. If masonry or brickwork needs to be removed or if access to ground level is difficult, then costs will also rise.

Damage Already Caused by Damp

If your home is already affected by damp, then you need to have any damage repaired before having a new damp-proof course installed. You need to factor in costs to repair any structural damage, such as broken brickwork or decaying timbers, as well as any costs needed for redecoration later on.

Remember, the earlier you catch problems associated with damp, the sooner they can be fixed. If damp is left to fester and spread, then the cost needed to remove it and repair any damage caused is always going to increase the longer it’s left.

For an accurate estimation of costs, you need to speak with a damp-proofing expert. There are several factors to consider, and a damp survey will need to be completed before the total cost of a damp-proofing project can be considered by a professional.

Contact Us for More Information About Damp-Proof Courses

If you’re looking to damp proof your home, then a damp-proof course is essential. From the initial survey through to installation, the expert team at Danford, Brewer & Ives is ready to help with all of your damp-proofing needs.

Contact our team today for more advice on installing a damp-proof course, or to book your initial survey and consultation.

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What is a damp proof course and how does it work?

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Damp is something that affects a very large number of properties and people at some point. Damp problems cause persistent headaches for many, many people during the home buying process and it can also be a real pain for landlords, tenants and homeowners alike. We know we don’t want it. We know we should try to avoid it – but very few of us actually know a great deal about it! Most of us have heard of some of the key terms associated with it – rising damp, for example. Another one is a damp proof course, but what is a damp proof course? What do they do and why do we need one?

Well, here are the answers to those questions and more…

The 3 main types of damp

To fully understand what a damp proof course is and how it works it’s worthwhile taking some time first to consider the different types of damp.

The symptoms of a damp-affected home are often very similar. Isolated damp patches might start appearing on walls. Walls themselves might feel damp to the touch. Plaster or paint might have visible cracks and may start flaking away. We might also see mouldy spots appear, and all of this is often accompanied by a fairly unpleasant musty, damp smell .

These symptoms and signs are usually caused by one of three types of damp. The first two actually often have little to do with the main subject of this post (a damp proof course) but they are worth explaining.

Penetrating damp – essentially when water penetrates through from the outside of a property to the internal walls, this is is usually caused by some sort of building or structural defect, such as a leaking pipe, a cracked guttering, for example.

Condensation damp – essentially a build-up of too much excess moisture in a property, this is is usually a result of poor ventilation in a home.

Although both penetrating damp and condensation damp can be very damaging to a property, and if untreated for long enough, can be quite costly, once the root cause is identified and correctly treated, they are problems that are relatively easy to address.

However, the third type of damp – rising damp – can be more troublesome and it’s with this type of damp that you really need to know what a damp course is.

A Damp Proof Course – Every home should have one

The problem with damp, in a nutshell, is that water rises. The technical term for this is capillary action . It’s also often referred to as wicking . Basically liquid (usually water) will naturally flow in narrow spaces (such as a wall). This means that, over time, an amount of ground water will naturally rise up through the wall or the floor of a building. Indeed, most floors or walls will allow some water to do so.

Along with the question: what is a damp proof course? Another common question is: What does a damp proof course do? Well, rising damp is usually stopped by the damp proof course. A damp proof course (DPC) is a barrier that stops the water from rising.

And every home should have one. At least, that is, if the property was built after 1875. Building regulations (Part C in England and Wales) ensure this. However, properties built before the regulations came into force may not – and a damp proof course doesn’t last forever. They become worn and damaged over time. When this happens, it is the usual cause of rising damp in a property.

Types of damp proof course

Newer builds usually have a combination of a damp proof course and damp proof membrane installed during construction. The damp proof course is often a horizontal strip of bitumen felt or plastic inserted 15cm above ground level. A damp proof membrane is a sheet of waterproof material inserted under a concrete floor. Together, the course and membrane seal a property and protect it from ground water.

However, this has not always been the case and although plastic is the damp proof course material of choice these days, it always used to be slate. Slate is a highly resilient material, more than up for the job of acting as a damp proof barrier. However, if the slate cracks or slips slightly out of position, the damp proof course ceases to be effective and will need replacing.

How can a damp proof course be replaced?

You’d be forgiven for thinking that it will be incredibly difficult and expensive to replace a DPC that has failed. In fact, it is now easier than you might expect.

Technological advances mean that a new damp proof course can be injected into the walls of a property. An injectable damp proof course is where a silicone or chemical liquid is injected through a series of 12mm holes running horizontally along the wall. The bricks soak up the waterproofing liquid creating a waterproof barrier 15cm above ground level. DIY kits are also available and a variety of creams and liquids can be used.

What is a damp proof course? It’s a frequently asked question, but now hopefully you have all the answers you need.

Related posts:

Can Injected Damp Treatments Damage Your Home?

Not only can injected damp treatments be a waste of money, they can also do untold damage when applied to homes that don’t need them

If you’re planning on buying an older property any time soon you could be entering into a world of unnecessary damp treatments. At the slightest whiff of  damp it’s not unusual for mortgage lenders to insist on a ‘timber and damp report’, withholding part of the loan as a ‘retention’ (typically around £2,000) which can only be released once any necessary remedial work has been carried out backed by a 20-year guarantee.

The trouble is, this approach often results in a lot of unnecessary work being carried out. At worst, damp treatments can be counter-productive,  damaging to the fabric of the property as well as being a complete waste of money.

When and why might damp treatments be recommended?

When you  apply for a mortgage , either to buy a property or to switch to a better deal, the bank or building society will normally instruct a panel valuer to carry out a brief inspection.

The reason why the spectre of damp has grown to such gargantuan proportions in the minds of bankers is that, left unchecked, it can potentially fuel devastating outbreaks of  rot and beetle infestation to structural timbers, with dire implications for the property’s market value.

Hence, even for straightforward valuation inspections, surveyors routinely arrive tooled up with damp meters to check moisture levels. If any damp is noted, a professional judgement needs to be made. Fortunately in most cases the odd spot of damp isn’t significant, and is easily remedied.

When purchasers commission a  private survey , such as a  RICS homebuyer report or building survey, the surveyor has a free hand to explain the type of damp along with any implications or action required. But when it comes to mortgage valuations, panel valuers appointed by lenders are often instructed to regurgitate standard pre-formatted phrases drafted by lawyers. Deviate from this and you risk being booted off the panel.

The following is a fairly typical phrase found in mortgage valuations under the heading ‘Essential Repairs’: ‘There is evidence of dampness to ground floor walls, and timbers in contact may be defective. You should instruct a damp and timber treatment contractor to investigate the full extent and carry out necessary repair work.’

This simple phrase has the effect of setting wheels in motion, assuming that the purchasers haven’t been scared off and decided to pull out, and before you can say ‘fungal decay’, a white van loaded with damp-proofing equipment will arrive on the scene, primed to do battle.

What are injected damp treatments?

Injecting a DPC involves drilling a row of small holes about 100mm apart into a mortar course just below ground floor joist level. A silicone-based fluid is then applied under pressure into the masonry where it hardens to form a chemical damp-proof course.

The question is, does it work? In theory the fluid soaks into the wall forming a horizontal barrier to block any damp from rising up. But in the vast majority of cases the DPCs are actually injected at far too high a level to protect floor timbers. And, instead of correctly injecting into mortar joints, the brickwork itself usually gets drilled, leaving a clear pathway for damp to get past the bricks via the mortar.

Adding insult to injury, these drilled holes are often left exposed — an open invitation to rain and frost damage. Furthermore, injected DPCs don’t work at all in thick stone walls. But the pièce de résistance is this: in order to qualify for the guarantee required by mortgage lenders, the installers hack off low-level interior plasterwork and apply waterproof cement render tanking to the inner face of the walls up to about 1.5m (it’s your job to redecorate).

This achieves the twin effect of obscuring poor installation while appearing to solve the problem because the wall surface is no longer damp. Then once the mortgage lender has received the guarantee (which may be worthless) the retention money can be released.

The trouble is, hidden floor timbers in contact with damp walls may still be quietly rotting away. Conservationists take the view that in period properties, injected DPCs can often make matters worse by adding additional barriers to breathability. Not to mention the fact that the lower walls are scarred with lots of unsightly holes.

Other treatments, such as fixing multiple vents to your walls, can be even more visually intrusive, pock-marking the brickwork until it resembles a climbing wall in the gym. The use of sealants designed to shield walls from rain can also prove detrimental if moisture enters the structure internally or via hairline cracks and becomes trapped.

How should I tackle damp?

The correct approach to solving damp problems involves identifying the true causes and remedying the source of the problem. The fact is, a properly maintained building shouldn’t need special treatments to manage damp effectively. Above all, it’s important that moisture is free to escape, which means using  traditional lime-based mortars and renders on older solid wall buildings .

In most cases, excessive external surface water can be diverted away and this, along with proper maintenance, can go a long way to resolving damp problems in lower walls and floors. An exception would be where walls below ground or basements may need lining with ventilated insulated cavities or  protective tanking . Cladding outer walls with tile hanging or weatherboarding can sometimes be a useful solution when penetrating damp is caused by persistent traffic spray.

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Chartered surveyor Ian Rock MRICS is a director is  Rightsurvey.co.uk  and the author of eight popular Haynes House Manuals, including the  Home Extension Manual , the  Self Build Manual  and  Period Property Manual .

Ian is also the founder of Zennor Consultants. In addition to providing house surveys, Zennor Consultants provide professional guidance on property refurbishment and maintenance as well as advising on the design and construction of home extensions and loft conversions, including planning and Building Regulations compliance.

Ian has recently added a 100m2 extension to his home; he designed and project managed the build and completed much of the interior fit-out on a DIY basis.

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Damp proofing, wet rot, woodworm and property refurbishment services in Dorset and Hampshire

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How does a damp proofing injection work?

How exactly does a damp proofing  injection work in preventing damp in your property and what is the method involved? We discuss all you need to know. We offer chemical injections with a 20 year guarantee as part of our damp proofing service.

How does a Damp Proofing injection work?

A chemical injection is the quickest method available to damp proof your property and involves injecting a damp proof cream into holes that are drilled into the mortar joints of your wall. The cream is designed to penetrate deep into the masonry and lines pores and capillaries with a waterproof coating in order to create a barrier against rising damp .

What is involved in a chemical injection damp proof course?

Both internal and external walls must be prepped properly before beginning a damp proof injection. If you are already suffering from rising damp, then you may see signs of a tide mark both on your inner and outer walls. It is important that you remove all damaged and contaminated plaster before proceeding with the chemical injection, as well as remove skirting boards and radiators in the area. Holes must be drilled to specific specifications, otherwise the effectiveness of the damp proof injection could be compromised. Holes should follow the mortar joints in a line and you should never drill directly into brick or stone.

Holes should be 150mm above ground level with a 12mm drill bit to a depth of 10-20mm from the opposite wall face and 120mm centres. This step is extremely important and can often be done incorrectly. It’s therefore wise to employ the help of a professional such as ourselves before attempting it. Finally, inject the cream using a low pressure sprayer into the drilled holes in the mortar joints and leave to coat the pores and capillaries of your masonry effectively.

We offer an effective chemical injection damp proof course to help protect your home against rising damp and it even comes with a 20 year guarantee! We are local experts in Dorset & Hampshire for all damp problems , contact us today !

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Damp Proofing Rods Explained

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Damp proofing rods.

Damp proofing rods are a simple and inexpensive way of doing a damp proof course (DPC). And, in a nutshell, that’s why we prefer them to other damp proofing methods such as chemical injection.

In the video, John explains how damp rods (sometimes called damp sticks) work. And why they are so effective in preventing rising damp.

He also shows you how where you need to install them to insure they properly take effect.

Other brands are available, but at HYPE Building, we use Dryrod damp proofing rods.

Firstly, because they are easy to install. Secondly, because they deliver exactly the right amount of water repellent material – known as silane concentrate. Hence, there’s no waste, like you can sometimes get with the injection cream.

This is the process for installing the rods:

Installing the rods

Remove the plaster.

Plaster is removed from the bottom of the walls up to a height of 1.5m. This is because rising damp can reach a height of up to approx 1.2m. Rising damp not only brings moisture but also brings hygroscopic salts, nitrates, and chlorides. By removing 1.5m of plaster, you are effectively eliminating any contaminated plaster.

Drill the holes

Holes are drilled into the mortar (usually the first layer of mortar after the first row of bricks from the floor) at the perpend junctions. So approximately every half-brick. The depth of the hole depends on the depth of damp proofing rod you require. We use Dryrods, which come in lengths of 180mm that can be cut to size. For walls thicker than 9”, multiple rods can be combined.

Insert the damp rods

The damp proofing rods are inserted into the pre-drilled holes and left to cure. Each rod contains exactly the right amount of water repellent material – known as silane concentrate.

Wait for the rods to take effect

Once cured, the silane concentrate seeps into the wall to form an extremely effective damp barrier. It will dry out the damp wall and stop rising damp from setting back in. You can actually see this happening. Once the water repellent material from one perpend has seeped sufficiently to reach the next, you know that the barrier has been formed.

Key moments in the video

0:09 – The plaster is removed from the bottom of the walls up to a height of 1.5m. Thus, eliminating any contaminated plaster.

0:52 – Holes are drilled at the perpend junctions. Usually at the layer of mortar after the first row of bricks from the floor.

1:09 – The damp proofing rods are inserted into the pre-drilled holes. Each rod contains exactly the right amount of chemicals.

1:36 – Once cured, the chemical water repellent (silane concentrate) seeps into the wall to form an extremely effective damp barrier.

Damp proof rods or cream?

A question we’re commonly asked is: should I use damp proof rods or cream to do a damp course?

And the answer is that it’s just down to preference. Both methods can work extremely well.

However, we prefer the rods for three main reasons:

Once the holes have been drilled to the correct length, inserting the damp proofing rods is a speedy process. And there’s no guesswork required on the amount you need.

Performance

Tests show that Dryrod damp proofing rods outperform even premium damp proofing creams at high saturation levels.

With cream, there is the potential for waste if you drill too far through the mortar. Creating a hole that’s too big could result in cream seeping out the other side. Therefore, we prefer the damp rods as they fit snugly into the pre-drilled hole. Moreover, they can easily be cut to size.

We’re experts in effectively eliminating damp

At HYPE Building, we’re used to solving damp issues in one form or another. Here’s a snapshot of what we do:

For property investors/landlords: A new damp proof course is usually part of a refurbishment. Going back to bricks allows us to ensure any existing damp problems are eradicated. And any future ones are unlikely.

For the people of Stoke-on-Trent: We’ve helped and advised on many damp issues for customers across the Potteries.

Here’s a great bit of feedback from a homeowner we recently helped…

“Very professional. Knew straight away what the issues were and gave me all the information that I needed to get them resolved. Highly recommended.”

John Bell – Homeowner in Mount Pleasant, Stoke-on-Trent

More helpful videos on solving damp problems.

You can watch the entire ‘Damp Causes and Fixes’ playlist on our YouTube Channel, HYPE TV. Below are two of the most-watched videos in the series that you may find useful.

Talk to an expert

Got a damp issue at your property in Stoke-on-Trent or nearby? Investing in The Potteries and need a DPC at your investment property? We’re here when you need us.

Click the button below and tell us how we can help.

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