How much does damp course injection cost? DIY & Professional

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how much does damp course injection cost

In this article we will be looking at how much damp course injections costs. As well as the advantages of doing it yourself or hiring a professional.

A working damp proof course (DPC) is very improtant in any property. If there is no DPC, there will be no protection against moisture rising through the walls. This happens when water is soaked up from the ground through capillary action. Rising damp can also occur if the outside ground level is higher than an existing damp proof course. This is known as bridging.

The cost of damp course injection will depend on a variety of factors. The main one is whether you do the job yourself or hire a professional. If you choose the DIY option, it will be considerably cheaper. You could quite easily install a chemical DPC for less than £100 in the average UK home.

This article will provide a rough guide for the costs of both a professional and DIY DPC injection. It also covers the pros and cons of each option.

Rising damp can cause a lot of damage if it is not treated. It can damage to the structure of your property. There can be serious cosmetic damage and can also affect building timbers, causing dry rot. This can lead to severe structural problems if not identified and dealt with soon enough.

Is it easier than installing a normal DPC?

Replacing an existing damp proof course is a difficult and complicated process. It involves a good deal of structural work. It is also a time-consuming and expensive process. So, a chemical DPC injection is the most common and cost-effective treatment.

The process itself is quite straightforward. If you are injecting from the inside you may need to remove any damaged plaster from the internal walls. Next, holes are drilled before injecting a damp proof cream into the holes. This forms a barrier against moisture. It is a job that many people will see as an appealing DIY project. There are a wide range of products on the market if you want to go down the DIY route.

Damp course injection cost – Professional vs DIY

The costs of a professional DPC injection will vary between areas and suppliers. But, as a rough guide, £70 per metre of wall treated is an average. This represents a cost of £275-£300 per wall.

These prices are just for the damp injection. It is other cosmetic work such as, re-plastering and decorating post-treatment that can really push the cost up. This is one of the main downsides of paying a professional to do the work.

One way of keeping the costs down is to have the plastering and decorating work done separately. You can remove the damaged plaster and inject the chemical DPC yourself. Following this, you can hire professionals to re-plaster and paint.  

There are many DIY injection kits available on the market. These are generally easy to use and will provide great results. Of course, you should always choose a good quality DPC to ensure the best results. But this doesn’t mean you need to spend a fortune.

Look for products that are BBA approved. This means the cream has passed a series of extensive tests.

One brand to look out for is Dryzone. Products are tested and BBA and WTA approved. A Dryzone Damp Proofing Kit comes with 5 cartridges of injection cream. A mastic gun and drill bit are also included. The kit is suitable for all types of job, large or small. You can read more including loads of reviews here on Amazon

Another option at less than £90 is Rempro DPC Injection Cream is BBA certified. It features a unique silicone emulsion cream. The kit received great reviews. Its also a bit cheaper than the Dryzone kit. You can click here to learn more and read some reviews

Before you install the damp proof injection

As with any home improvement task, the key is in careful preparation and pre-treatment. If you do have damage internally, you may need to remove skirting boards, and possibly radiators if they present an obstacle. Also, any damaged plaster needs to be removed. Plaster is usually removed to a height of around 1 metre. If damp has risen higher, the plaster will need to be removed to 300mm above the highest point of the damp.

Once the pre-treatment is complete, the damp proof injection can occur. Holes will be drilled horizontally into the mortar. A cartridge gun is then used to inject the damp proof cream into the boreholes. The cream will then work its way through the mortar via capillary action.  This will create a barrier against rising moisture.

After the damp proof injection, the internal walls will need re-plastering. Ensure the walls have time to completely dry out before applying new plaster.

Injecting a DPC into an outside wall

Most damp proof course injections are carried out because rising damp is found in a property. Typically, there is visible damp and tide marks on the walls. Other signs of rising damp are peeling wallpaper and paint. Further issues may occur if the rising damp has gone untreated for a long time. You may notice that the skirting boards or even the flooring has begun to rot.

Signs of rising damp are generally found on the interior walls. Therefore, DPC injections tend to be from the inside. With that said, you can also inject a DPC from the outside. Of course, this would mean there is no need to remove plaster before injecting. You just need to drill holes into the mortar and inject the cream.

If this is a cavity wall and you are injecting both sides, these will both need doing separately. You will need to inject the DPC into the outside skin from outside, and into the inside skin from the inside.

How does a damp proof injection work?

The way a damp proof injection cream is installed is simple and straightforward. Holes are drilled into the mortar joint. The damp proof cream is then injected into the holes. DPC creams work because they contain silicone. The silicone penetrates the mortar’s pores in the brickwork or masonry. This creates a waterproof seal. This water repellent barrier forms a full protection against rising damp.

Research shows that DPC creams with a low silicone concentration are less effective. The silicone concentration is worth checking. UK testing and certification does not take silicone content into account. But it is its concentration that determines its performance.

Common mistakes to avoid with a DPC injection

A damp course injection can be completed as a DIY project. If you want to keep costs down, then doing it yourself is the cheapest option. It is worth bearing a mind that there are several common mistakes which happen. These can be costly and lead to a property having worse damp problems. Often these mistakes result in the damp having to be treated from scratch. This increases the costs incurred.

The most common mistakes made, stem from an initial misdiagnosis of the damp issue.

Errors also occur if the damp proof cream is incorrectly injected. If professional and expert advice is not sought, an existing DPC might not be identified. This means you inject a second DPC, when there was already a functioning one.

Not drilling into the mortar line and drilling into the brick or stone will also cause problems. It is important not to apply the DPC cream into pre-existing holes. This is where a previously installed DPC has failed.

Care is needed if there is a bridging of cavity walls where the injection takes place. Over time the gap will become filled with debris. This can end up compromising the damp course when moisture begins to seep through.

Finally, a DPC will not be effective if the injection is into a damaged or low-quality mortar joint.


A chemical DPC can be an excellent way to protect your property from rising damp. So, how much does damp course injection cost? The truth is the cost will vary based on several factors. But if you do end up doing it yourself, it can actually be quite a low cost job.

DIY kits provide everything you will need to install your own DPC. This will usually include detailed instructions. The only thing you will need that is not provided is a drill for creating the holes needed to inject the DPC cream.