Penetrating Damp

Rainwater goods

Gutters and Drains:
Leaking or overflowing gutters and drains are common causes of dampness. They can be difficult to identify in dry weather, so we ask you to look closely at the gutters and drains when it rains.


There are often tell-tale signs, such as a damp stain, greenery or “efflorescent” white streaks. The resolution is often easy, involving a ladder and time to clear the blockage or fix the leak.

External Coverings; Roofs, chimneys, flashings, render

Our survey is not an assessment of the state of roofs, chimneys, flashing, render etc. We look externally for defects and then search internally for signs of dampness. We recommend regular annual integrity checks of external coverings including roofs, chimneys, flashings, render etc.

External Vents: It is important for timbers to be properly ventilated, either in the subfloor void, for floorboards or in the loft for roof timbers. Vents can become blocked over time providing inadequate circulation of air to ensure vapour movement from timbers.


Exterior Ground Levels: The ground immediately surrounding a property is often raised by successive owners to the point where there is very little clearance between the ground and ventilation grills. In the worst cases water flows under the floorboards. Vents should be clear of the ground, ideally higher than a rain drop bounces. Rain water bounces 100-500mm depending on any overhangs, such as window ledges, the type of ground and run off of water. Vents should be observed and recorded during a rain storm – we are happy to analyse results.

If there is sufficient ventilation, a small amount of water entering will evaporate without causing rot. If too much water is entering, then the resolution is a small trench (French drain) about 150mm by 150mm, which can be dug around the vent or perimeter of the exterior wall and filled with shingle or similar material, with drainage. This need not be laborious.

Misdiagnosis condensation, as penetrating damp through chimney

Damp Surveys – problem damp in lower ground floor flat Misdiagnosis An independent surveyor missed the obvious signs of condensation. Sad, because you expect contractors to misdiagnose damp, after all “they are incentivised to sell”. A cold November day, 4 people living in a two bedroom lower ground floor flat, no extractor fan in kitchen nor bathroom …

Misdiagnosis condensation, as penetrating damp through chimney Read More »

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