How to I prevent raising damp in a wall

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How to I prevent raising damp in a wall

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Rising damp is one of the most obvious and unpleasant “features” of a home and can significantly devalue properties.

As dampness “travels”, the source of the problem often isn’t where it appears on the wall. We use a tool called a “damp-meter” to assist us in isolating the source of the problem. This ensures that we locate the exact point in which water is getting into the wall, so that we know our remedy will in fact cure the problem.

There are different remedies available depending on what is required to solve the rising damp issue.


Waterproof Membranes - This is a method of treating rising damp particularly on single brick or solid limestone walls or below ground level walls. In this case, any existing effected render is removed, usually to a meter high, leaving the brick work or limestone exposed. We then coat the surface with a fibreglass, waterproof membrane before re-rendering.


Dampproof Coursing - A damp-proof coursing is what prevents water from rising in the walls and from there causing further damage. When this damp-proof coursing breaks down through age and wear etc, combined with the mortar eroding and breaking down, this allows moisture to penetrate the walls. The remedy for this is to cut out the lowest course of bricks and replace the deteriorated damp-course membrane with a new one before replacing the bricks.


Internal/External - Rising damp can affect both internal and external walls. Watering systems, or heavy weather conditions can subject external walls to rising damp. Visible signs for external walls include fretting mortar, paint/render peeling off or salt marks on the bricks The two main causes for rising damp on internal walls are both a breakdown of the original dampcourse plus rubble between the walls in the cavity. Signs of rising damp for internal walls include bubbling paintwork, a damp smell or a watermark. The remedy for both, is to remove the render or plaster, leaving the bricks exposed, cut out the lowest course of bricks, clean out the cavity of all debris, replace the bricks and then re-render or plaster once again, ready for painting.


Cavity Cleaning - The amount of rubble which accumulates between the internal and external walls can be surprising. Without cleaning this out, damp-proofing is much less effective as water still has a "bridge" to travel through - this is how the water gets from outside to inside! When the original bricks were laid, the visible joints (internal wall and external) were finished cleanly. However the joints on the cavity side of the wall were not "finished", leaving overhanging mortar which over years has broken off and fallen into the bottom of the cavity between the walls. By thoroughly cleaning this out, the damp-course membrane which is inserted into the wall can now be effective. Without cavity cleaning, the silicone method of damp-proofing is less effective as water still has a bridge to travel through.


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