As damp proofing and timber specialists, we routinely tend to properties with all manner of damp issues, including rising damp. It’s a common issue in older homes, of which there are more than 12.7 million in the UK. In fact, more than 38% of homes pre-date 1939, meaning a good portion of homes have old damp proof courses (DPCs) that are likely compromised or not up to modern standards. A compromised DPC is one of the leading causes of rising damp, of which a DPC injection cream may be used.
DPC is a barrier that is installed when a house is first built, although some older period properties may not have a DPC at all (pre 1870 as a general rule) Where an original DPC is present, it will typically appear in the form of a thin band running horizontally between brick courses at low level, preventing water and moisture from the ground-penetrating the walls and causing rising damp through capillary action.
The membrane itself can be made of either plastic, slate or lead-lined bitumen, all of which are effective waterproof options. No matter what material is used, it should be placed close to the ground (minimum of 150mm), lower than suspended timber floors to prevent timber issues.
DPC may also come in the form of a DPC cream, and this is usually implemented in instances where the original DPC has been compromised.
There are several ways a DPC can become compromised, with the most common cause being age. Even modern DPCs don’t last forever.
Other reasons a DPC may become broken or compromised include:
You will likely know if your DPC has become damaged or compromised in any way because you’ll likely experience symptoms of rising damp. This can present itself in the form of:
If you notice dampness on the upper level of your house or higher up the walls, this could be a sign of penetrating damp which is a different issue altogether and requires a different treatment approach. Rising damp doesn’t exceed 1.5m in height due to gravity, but damp lower down the walls isn’t necessarily rising damp. Water ingress, defective guttering, poor render and penetrating damp can also present themselves in this way.
In the event you notice any signs of damp, you should call a damp specialist. The Garratt’s Damp & Timber team works across London and parts of the south east, so if you’re in our catchment area, get in touch with us. We offer a free site survey to determine the cause of the damp, and we then provide you with a no-obligation quote for treatment.
If your property has a compromised DPC, there are several treatment options, but the one we recommend will differ depending on individual circumstances. The most common form of treatment is a damp proof injection cream. A chemical DPC is typically used, with the active ingredient being silane.
A series of holes are drilled and the solution is injected. It penetrates the mortar bed of the property, absorbing into the substrate before curing. When cured it forms a water repellent barrier.
In addition to the DPC injection, other work may be required, such as removing damp plaster or plaster with salt bands, replacing affected masonry and/timber, and re-decorating as necessary.
Rising damp will have deposited various ground salts into the plasterwork, these salts absorb atmospheric moisture and continue dampness and thus replastering regularly goes hand in hand with DPC injections.
For this reason, we never recommend you treat your DPC by yourself. Doing so could cause more damage than it fixes.
DPC cream is a highly effective form of treatment and is one that our team uses regularly. It’s one of the most widely used remedies for properties suffering from a compromised DPC due to its efficacy. We use high-silicone content DPC creams.
Not all damp proofing specialists do as there is little to no governmental guidance on the chemical content used in damp proofing injections. This means some creams on the market are below 10%, and tests reveal that a concentration below 10% can be ineffective.
When you organise a DPC injection through Garratt’s Damp & Timber, you can rest assured that the injection cream we use has a high silicone concentration and will protect your home from the risk of rising damp.
If you think your property might be suffering from a compromised DPC, contact us to organise a free site survey.