Many damp issues are not caused by a failure of the original damp proof course, but instead by alterations carried out to the property over time. Whether it’s the installation of a new patio raising external ground levels, paths or driveways bridging the damp proof course, or, like in this case we are going to look at today, external render being applied below DPC level, these changes can all allow moisture to bypass what was originally an effective barrier.
I was called out to a property to carry out a damp investigation in Liverpool to find the cause of dampness to a front elevation external wall.
As shown in the photograph above, the external render had been applied down to ground level. This effectively covered the original damp proof course, allowing ground moisture to bridge the barrier and track into the property.
This is a clear example of how later alterations can lead to damp issues, even when the original damp proof course remains intact and functional.
Following discussion with the homeowner, a section of the render was carefully removed on-site to expose the original damp proof course. The image below shows the now visible bitumen DPC, confirming that the issue was not a failure of the damp proof course itself, but bridging caused by the render.
The next step is to reduce the external ground levels to ensure they sit approximately 150mm below the damp proof course. This will help prevent moisture from bridging the DPC in the future and allow the wall to begin drying out naturally.
This case study demonstrates how damp problems are often caused by property alterations rather than a failure of the damp proof course itself. Correctly identifying the source of the issue is key to avoiding unnecessary and costly treatments.
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