Roof Drainage System Issues.

Posted 26th May 2024 / News.

Dampness in residential dwellings is frequently traced back to faulty rainwater systems, notably gutters and downpipes. Statistics show that as many as 1 in 5 Properties grapple with ineffective rainwater disposal mechanisms, leading to heightened dampness concerns.

 PVC has become the material of choice for most contemporary gutter and downpipe systems due to its durability and cost-effectiveness. However, in older properties, cast iron was the predominant material used. Even after the gutters have been upgraded to PVC, it is common to find original cast iron downpipes still in place. Unfortunately, cast iron is susceptible to corrosion, particularly when neglected over time. Instances of deterioration are frequently observed at the rear of cast iron downpipes, which may have endured years without proper maintenance or painting.

 When gutters lack the necessary capacity to manage the volume of water runoff from the roof, overflow becomes inevitable, especially during heavy rainfall or on expansive roofs. Additionally, gutters are prone to obstruction from leaves, moss, and other debris, leading to blockages that force water to back up and overflow. This overflow, in turn, saturates the walls beneath, potentially causing damage to the exterior surfaces of the building.

When a solid wall becomes saturated, the resulting dampness can infiltrate the interior, leading to damage to decorations and potentially compromising other elements of the building’s structure. Furthermore, saturation of an external wall often results in frost damage, characterized by spalled brickwork and degraded pointing. This deterioration exacerbates the wall’s porosity, worsening the damp issue.

Valley gutters, running at the intersection of two roofs, and box gutters, situated centrally on inverted pitch roofs, are particularly prone to failure. Typically fashioned from lead, these gutters demand precise detailing to ensure they remain watertight and can accommodate thermal movement. If a valley or box gutter fails, it can result in water infiltrating directly into the roof space, particularly if the sarking felt is compromised or non-existent, posing significant risks to the building’s integrity. It is estimated that 1 in 12 Box Gutters are defective.