How long does a chemical DPC last?

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A chemical DPC, can be a good alternative to replacing the original damp proof course in your property. This is mainly because a chemical DPC is extremely easy to install.

how long does a chemical dpc last

On the other hand, reinstalling the original DPC, is not quite as simple and does require some structural alterations. Because of this, it is not really a DIY job and will usually require the help of a professional.

So, is a chemical DPC as effective as the original DPC in your property? And how long does a chemical DPC last?

A good quality DPC, that has been correctly installed will last for 20+ years. If you have it installed by a professional, most companies will guarantee your new chemical DPC for 20 years. With that said, there are very good quality DIY kits on the market.

In most cases, a professional is not necessary. Installing it yourself is quite straight forward and most DIY kits will still offer a 20 year guarantee.

The original DPC in a property, will usually last longer than a chemical damp proof course. However, this is installed during construction. For this reason, it is not always a viable option to replace the original.

A chemical DPC, is far more simple and can usually be completed in a couple of hours.

What is a damp proof course?

A damp proof course is a waterproof barrier. It is usually installed roughly 150mm from ground level. In new build properties, this is installed in the mortar of the brickwork a couple of bricks up. Most properties will already have a DPC. depending on the age of your property, the material this is made of could be slightly different.

For example, in old properties, this could be made of slate or other non-porous building materials. In more modern builds, it will usually be plastic, or something like a bitumen painted onto the bricks. Finally, in some older properties a damp proof course will not be present at all.

Whatever your damp proof course is made of; it has the same intended purpose. This is to stop ground moisture from rising into your property. Whilst rising damp is less common than condensation or penetrating damp. when it does occur, it can be one of the most damaging forms of damp in a property.

No matter what your damp proof course is made of, it will fail eventually. Nothing lasts forever and overtime the quality of the existing damp proof course will degrade. Once this happens, it will begin to let small amounts of water through. This could be due to your plastic damp proof course becoming damaged or degraded. If you are using something like slate, cracks may have formed that water is able to seep through.

Whatever the issue, you will want to repair the DPC at the earliest possible point. This will avoid damage due to untreated rising damp.

Why use a chemical DPC?

So why should you use a chemical DPC? Why not just reinstall something like the original damp proof course? The answer to this is quite simple. Most original damp proof courses are added during the construction phase. Which means that replacing them will require some structural alterations. This will usually include removing bricks and reinstalling.

The process takes a good amount of time and effort. Also, it is not recommended that this type of work is performed by the homeowner, as a DIY project. Because you are removing bricks, this is affecting the structural integrity of the building. If you are not professionally trained, you could end up causing irreversible structural damage to your property.

When an original damp proof course, such as plastic or slate is replaced manually. The builder will remove a small number of bricks at a time. they will then insert a new damp proof course and refit new brickwork. This will be done in small sections, to protect the structural integrity of the wall.

You can see a video of this process below:

As You can see, this is not a straightforward process and will require somebody with building and structural knowledge. This means that reinstalling an original damp proof course can be quite an expensive job, as you will be paying for materials, as well as labour.

The advantage with the chemical DPC, is it is very easy to install. The entire kit will consist of only a few parts:

  1. The tubes of chemical DPC cream
  2. A mastic gun for applying the cream
  3. 12 millimetre drill bit for drilling holes
  4. Finally, you will need an SDS drill to drill the holes.

Most chemical damp proofing kits come with easy to follow instructions. These will tell you exactly where to drill the holes and how much chemical DPC cream you need to inject.

Most kits will recommend you drill holes at around 120mm intervals. This will allow the cream to fully penetrate the pours of the mortar, creating an effective waterproof barrier.  

How long does it take for a chemical DPC to start working?

It usually takes around 4 weeks for a new chemical DPC to completely cure. After this point it should have formed a fully waterproof barrier in your mortar. This will completely stop any further damp rising past this point.

You will also need to allow time for any rising damp to dry out. This may require some remedial work inside your property. Especially if the rising damp has damaged plaster, woodwork, and decorations. If your walls have become saturated due to rising damp it could take up to 6 months for this to completely dry out.

You can increase drying time by heating the area and allowing good airflow by opening windows and doors. You could also consider using a fan to aid with air circulation. Also, a dehumidifier could help to extract more moisture.


A chemical DPC is a good option if you need to install a new damp proof course. They are very affordable and if installed correctly, they should last for 20+ years.

They are also very easy to install. So, for the majority of people, this should be a straightforward DIY job.

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