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The Guide to Damp Proof Injection

Red brick wall with old fashioned slate damp proofing

A damp-proof injection to install a Damp Proof Course (DPC) in the walls of your building should only ever be carried out by a qualified professional. When a DPC has not been installed correctly, it is about as useful as not having one at all and the damage can result in the requirement of costly repair work.

Our team is highly skilled and have years of experience providing wall injection damp proofing and will be more than happy to talk you through what the best methods of damp proofing walls are. The age of the building and its location are factors that our team will take into consideration amongst other things, which is why a thorough property survey is always recommended before any work begins.

Why a Damp Proof Injection Would be Needed

A damp-proof injection is required to either repair a damaged DPC in a wall, likely diagnosed following the appearance of rising damp, or to install a new injection mould DPC. Some older buildings were constructed with slate material used as a DPC, although this is prone to cracking which would make the protective barrier easy for moisture to penetrate.

Additionally, in the event of a bridged DPC, which is when the external ground level has risen above that of the barrier, an injection may be required. The external ground would first have to be lowered to bring it back below the height of the DPC (there should be a minimum of six inches of space between ground level and the DPC) before an injection.

Injection of Chemical DPC

A chemical DPC is the most common way to provide a waterproof later within the mortar. The chemical DPC can be made using a variety of products and chemicals and almost always appear as a gel or cream. The reason why damp proof injection is the favoured method of installing a new DPC is that the introduction of a physical DPC is much more difficult, time-consuming, and expensive.

How Our Team Installs a Damp Proof Injection

Before any invasive work, our team will ensure that the correct amount of gel or cream is used, as well as ensuring that the thickness of the wall is suitable as per the method of injection. Depending on the thickness of the wall, an injection may be required from both sides so as the DPC provides adequate protection.

A 4.5-inch-thick wall can be injected from either side, requiring a damp proof injection on one side only. A 9-inch-thick wall can be injected from either or both sides depending on the type of chemical DPC. Anything thicker will need an injection on both sides to protect against damp rising through the wall.

After carrying out the relevant measurements and checks (such as for high ground levels and internal and external leaks that may result in penetrating damp), the team will begin to drill 12mm holes in the wall (at least six inches above ground level) spaced 115mm apart into the mortar. The deepness of the hole will be dependent on the thickness of the wall:

  • Half-brick walls (115mm) – 100mm deep holes
  • One-brick walls (230mm) – 210mm deep holes
  • One-and-a-half-brick walls (345mm) – 320mm deep holes
  • Two-brick walls (460mm) – 430mm deep holes

The chemical DPC is then injected via a skeleton gun from the bottom of the hole outwards until it is filled. Once completed, the hole is either closed with a plastic plug fitting or capped with mortar. Repainting and plastering may be required upon completion of the wall injection damp proofing to clean things up from an aesthetic point of view if you do not want signs of your new DPC installation being visible.

How Long Does the Work Take?

The length of time it takes to complete a damp proofing injection depends entirely on the size of the property. At a minimum, you should expect at least two days for the project to be completed with the average being between three and four days, while larger jobs can take a week from beginning to end.

When you get in contact with the Garratt’s Damp & Timber team, we can arrange for a property survey where we can come and inspect the property and offer a no-obligation quotation and lead time, as well as running you through some of the finer details. Our experienced team of experts will be best placed to offer any advice and answer any questions that you may have in regards to a damp proof injection in your property, as well as any other damp-related question that you may have.

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