What Is Damp Proof Injection and How Does It Work?

We know how alarming it can be to notice signs of damp in your home. After all, if left untreated, it has a bad reputation for causing complex structural damage.

The damp-proofing injection works wonders for the majority of moisture-related problems. It helped numerous homeowners maintain the structural integrity of their homes while also preserving the internal aesthetics of the walls and floors.

In this article, we'll go over everything related to this damp-proofing method so you can understand how, when, and why it's used!

What Is Damp Proof Injection?

Damp-proof injections are a type of damp proofing that's used to treat rising damp and manage moisture buildup in the home's interior.

You’ll usually find these injections applied in buildings where the existing damp-proof course (DPC) has failed, so they're more like a corrective measure.

How Does Damp Proof Injection Work?

The idea behind damp-proof injection is to create a shield that repels water inside the walls. This is accomplished by injecting a specialised chemical solution into the walls, which spreads throughout the brickwork and forms a barrier against moisture penetration.

What Is the Process of Damp Proof Injection?

The damp-proof injection procedure is pretty straightforward; we can sum it up in the following three steps:

  • Drill horizontal holes (with specific measurements) into the wall’s mortar joints
  • Inject the damp-proofing solution into the holes
  • Allow the solution to dry completely before performing any additional work on the wall

What Are the Different Types of Damp Proof Courses?

When it comes to damp proofing, you might find lots of jargon that can be perplexing. So, to help clear up any confusion, we'll answer some frequently asked questions about the various types of DPC.

What Is Membrane Damp Proofing?

Damp-proofing membrane (DPM) is one of the main types of DPC. It's a layer that’s usually placed along the wall's foundation during the construction process to keep moisture out. However, we can still easily attach it to an existing wall when necessary.

This membrane comes in a variety of materials, the most common of which is polyethene.

What Is Chemical Damp Proof Injection?

The majority of houses are built with DPC nowadays, but they can deteriorate over time, leaving some areas compromised. This is where DPC injection comes into play.

The chemical damp-proof injection is another major type of DPC, and we mainly use it to restore the water-repellent functionality in the defected areas.

What Is Silicone Injection?

Silicon fluids were among the first materials used in DPC injections. The silicon would seep into the pores of the masonry, preventing water molecules from settling in.

That said, this material required high-pressure injections and was later found to be less effective than creams.

What Is Cream Injection?

Damp-proof creams proved to be one of the most effective materials for dealing with rising damp. Although it requires low pressure, it's developed to travel deep inside capillary pores in the walls to form a strong horizontal barrier.

It's worth mentioning that one of its key ingredients is silane, a silicon-hydrogen compound; in layman's terms, it's a silicone-based chemical.

Where Do You Use Damp Proof Injection?

In general, damp-proof injections are applied 150mm above ground level. This is the point at which you should start drilling horizontal holes 12mm in diameter and 10-12mm in depth.

Do You Apply Damp Proof Injection on Internal Walls?

Although external damp-proof injection is usually preferred, it may occasionally be necessary to inject the wall from both sides, which is why you should have a professional inspect it first.

Can You Use Damp Proof Injection in Bricks?

You should always inject the DPC chemical into the mortar line rather than directly into the bricks, as doing so can prevent it from spreading properly and thus performing as intended.

Can You Use Damp Proof Injection in Cavity Walls?

Yes, you can apply a DPC injection from both sides of a cavity wall. That said, to ensure that moisture doesn't affect it, the cavity should run a minimum of 225mm below the damp-proof course or have a cavity tray with weep holes (small openings) every 900mm.

What Is the Cost of Damp Proof Injection?

The cost of a damp proof injection varies depending on several factors, including the severity of the case and the size of the property. However, we can say that it ranges from £1,000 to £5,000.

How Much Does a Damp Proof Injection Kit Cost?

You’ll find many DPC injection kits on the market, including the necessary tools, such as damp-proof cream, drill bits, and an injection unit. The cost of each kit differs based on the brand, with prices ranging from £70 to £300 and higher.

What Are the Benefits of Damp Proof Injection?

Using chemical injection comes with plenty of benefits, the most significant of which is that it stops moisture from rising inside the walls. This problem, known as rising damp, can damage wall finishes, cause wet rot, and result in structural damage.

Another great benefit is that having a good damp-proof injection applied can increase the market value of your property!

What Tools and Equipment Are Required for Damp Proof Injection?

Although the specific tools we use for DPC injection can vary depending on the case, some of them remain constant:

  • Drill: A heavy-duty drill that easily bores holes in mortar joints
  • Masonry Drill Bit: 12mm masonry drill bits, which are sturdier and can drill through thick concrete without bending
  • Injection Cream (or other damp-proofing material): Expands horizontally inside the wall to form a water-repelling layer
  • Injection Gun/Pump: It applies pressure to the injection cream to properly force it into the drilled holes in the wall

How Do You Prepare the Area for Damp Proof Injection?

The first thing you should look for is whether the trapped moisture affected the plaster on the wall; if so, you need to start by removing the damaged areas.

Then, to gain better access to the brickwork, you must remove any obstructions that may be in the way, such as radiators, skirting boards, or similar.

Should You Hire a Professional or DIY for a Damp Proof Injection?

While a DIY damp-proof injection project may appear tempting and budget friendly at first glance, it's not always the best course of action.

Throughout our years in this industry, we've seen several cases where we had to fix failed projects that ended up costing more than if a professional had handled it from the start.

To explain, identifying the main source of the dampness and its severity calls for specialised knowledge. Then, based on our findings, we determine the best method and materials to deal with each case.

Without prior experience, there's a good chance the injection won't be performed correctly, which may not solve the issue or may even make it worse.

How Long Does Damp Proof Injection Take To Work?

The chemical injection usually takes 4 to 8 weeks to fully cure and form a protective barrier inside the wall.

Factors Influencing How Long Damp Proof Injection Takes to Work

In some cases, the DPC injection is distributed at a faster rate than in others. To help you understand why, we've listed the primary factors that affect how long the process takes and even how well it works:

  • Moisture and salt content trapped in walls
  • Size of pores and property construction
  • Type of chemical injection
  • Accuracy in performing the injection

What Happens After Damp Proof Injection?

When we finish injecting the walls, we stop working on them for as long as possible to allow the damp-proof material to dry properly.

Following that, we resume replastering the walls internally and reinstalling any structures that we've removed. After a while, we evaluate the treatment's effectiveness.

How Long Does Damp Proof Injection Last?

This type of damp proofing has a lifespan of 20-30 years or can last as long as the building.

Factors Affecting the Lifespan of Damp Proof Injection

The quality of the materials used, as well as the precision of the injection, are two of the most critical factors influencing its lifespan. It's also important to keep in mind that untreated conditions, such as leaking, can reduce the effectiveness of the treatment.

How to Make Damp Proof Injection Last Longer

To get a long-term solution, you should start by addressing the underlying cause of dampness before any further action.

When it comes to injecting, there are a few inspections that must be made to ensure a successful, lifelong treatment. One of these is to avoid drilling into damaged mortar joints or injecting into pre-drilled holes where the initial DPC has failed.

Overall, it's a delicate process that requires meticulous examination and the use of high-quality materials. That’s why hiring a professional is essential to extending the treatment's lifespan.

When to Use Damp Proof Injection?

There are some situations where damp-proof injection becomes necessary. For example, if you live in an area with high moisture levels or in a building where the original damp-proof course is no longer functional, and most importantly, if you saw signs of rising damp.

What Sets Damp Proof Injection Apart From Other Treatments?

Each damp-proofing treatment is best suited to a specific set of conditions. However, you'll notice that damp-proof injection is generally preferred in many situations, and this is due to the unique benefits it brings to the table:

  • Time-Saving: When compared to other damp proofing methods, this one takes far less time and effort. It mainly entails removing the plaster from the wall and drilling holes. This makes it one of the most time-saving solutions.
  • Cost-Effective: Given how effective damp-proof injection is at locking out moisture, its application comes at a reasonable price.
  • Long-Term Solution: Unless there are underlying issues, using chemical injections takes your mind off any future damp-proofing treatments. It has an extremely long lifespan, possibly lasting a lifetime!

What Are the Signs of Rising Damp?

As you may already know, various types of damp can affect your home. It's critical to figure out which type you have so that you can choose an appropriate damp-proofing method.

To ensure that the problem you're dealing with is rising damp, always look for the following five signs:

  • Damp patches and tidemarks on the wall
  • Peeling wallpaper or crumbling plaster
  • Salt residues on the wall (looks like white powder)
  • Rising floor coverings
  • Decaying timber

How Does Rising Damp Happen?

Rising damp simply occurs when groundwater enters your building's structure and begins to move upwards.

Multiple scenarios can result in this problem. As we previously mentioned, it could be because the pre-installed damp proof is worn out, but in other cases, poor drainage could be the culprit.

Rising damp can also take place when the DPC installed in your home is lower than the ground level outside, allowing water to seep in above the treatment.

What Are the Other Methods of Fixing Rising Damp?

Although damp-proof injections are among the most widely used treatments for rising damp, there are a few alternatives.

Damp-Proof Paint

It's normal for the building's structure to absorb some moisture, which can cause tiny damp spots on the wall. If that's the case, you can simply coat this small area with high-quality waterproof paint.

However, if you've noticed the rising damp spreading, this technique won't be much help, which brings us to the second option.

Damp Proof Membrane

When the rising damp case is severe, a physical DPM can be installed instead of a chemical injection.

In a nutshell, this process involves cutting through the mortar bed horizontally and inserting the membrane to act as a moisture repellent; it's quite similar to the shield created by the injection.

Nonetheless, as you might expect, this method causes more structure distortion than DPC injection.

Lower External Ground Level

If you hire a professional to investigate the dampness problem, you may discover that it has nothing to do with the current DPC. If the rising damp happened because the external ground level is higher than the DPC, you can have it lowered (if possible).

Where Do You Normally Get Rising Damp?

Since rising damp occurs when groundwater moves up and saturates the capillaries in masonry, it becomes most noticeable on the internal walls of your home. Besides, water can sometimes accumulate beneath the ground, causing the flooring to appear defective or damaged.

Are There Any Legal or Regulatory Requirements for Damp Proofing?

First off, Approved Document C in building regulations made it mandatory for buildings in England to have DPC in the walls and DPM in the flooring. We should note that this regulation was implemented in 1875, which is why structures built before that date may lack proper damp proofing.

You can use Document C as your comprehensive guide for damp-proofing-related regulations, and some of them are as follows:

  • DPM in the flooring must be continuous with DPC in the walls
  • DPC should be applied to the joints between windows and doors to prevent precipitation from entering the building
  • DPC in exterior walls should be at least 150mm above ground level (subject to change)

Do You Need Any Insurance for Damp Proofing?

Actually, not really, as most insurance policies issued for buildings or their contents don't cover cases of damp-related damages.

What Is Damp Proofing Cream?

The cream used in DPC is a water-repellent substance that's chemically developed to expand through masonry capillaries.

When you allow it to settle after injection, it transforms into a liquid that's absorbed into the surrounding brickwork and mortar line. This moves the cream's water-repelling properties to the injected areas of the masonry wall to help it prevent moisture from rising inside it.

Which Type of Damp Proofing Cream Is Best for Your Needs?

Consult a professional about which damp-proof injection cream you should use, as it'll differ from case to case. Nonetheless, the best types on the market are typically those with a high silane concentration, as it plays a significant role in forming a powerful barrier.

Does Damp Proofing Cream Need to Be Injected?

Yes, the damp-proof cream must be injected into the mortar line via a slim nozzle attached to the injection gun in order to work. That is, to reach the inside of a wall and form an adequate defence. However, no high-pressure injection is required; simply applying hand pressure will do.


If you suspect that your property is suffering from rising damp, you should have it inspected as soon as possible before it worsens.

The good news is that with damp-proof injections, you have nothing to worry about. The process is quite smooth as it doesn't require major construction work on the masonry walls, only drilling small holes, and it's also completed fairly quickly.

Get in touch with us now to have your home inspected and treated effectively!

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