Debunking Damp in Ageing Housing Stock

Damp can be a persistent problem in older properties if not tackled correctly. With much of the UK’s social housing provision coming from the repurposing of older properties. One of the biggest challenges for local authorities and housing associations is finding cost effective ways of keeping damp at bay.

What causes damp?

Damp is caused by excess moisture being trapped in the structure of a building, which can lead to mould growth and, if left untreated, significant structural damage.

Damp isn’t a new problem and can be a nuisance in older properties. There are many reasons why it occurs, and even though rainwater, condensation, and an improper damp proof course (DPC) may be the more obvious causes of damp, a common cause which is often overlooked is the use of incorrect building materials.

Unbeknown to many tenants, local authorities, and housing associations, using modern building materials in older properties, such as cement render, cement-based mortar, and modern paint/wallpaper, can facilitate damp, as they don’t allow excess moisture to pass through the walls and escape a building.

Incorrect plaster choice

Humidity and condensation are often unavoidable, particularly in older properties which tend to have thicker walls, and lack the insulation and damp proofing we are used to in more modern properties.

One building material which can be particularly troublesome in these types of buildings and can cause damp, is a Gypsum based plaster. Gypsum based plaster is impermeable, meaning it easily absorbs and retains moisture from the surrounding atmosphere and substrate, making it highly susceptible to damp and black mould growth.

Since the 1960s, Gypsum based plaster has been a ‘go-to’ solution for many contractors, particularly within local authorities and housing associations, as it is cheap and easy to use. However, it only provides a short-term solution, as after just a few years, it will have retained water to the point that damp occurs again.

Preventing damp

The alternative to gypsum based plaster is to use a lightweight renovating plaster. Its breathable properties allow moisture to pass through it and the fabric of the walls, preventing damp and mould growth. Renovating plasters, such as Limelite from Tarmac, are more sympathetic to the characteristics of older properties and due to their breathable nature, can even be used on areas which have previously suffered from damp or flooding. Limelite includes a salt inhibitor which provides a barrier against salt transfer and efflorescence to protect the decorated finish of a surface. It provides a fast and effective long-term solution for damp remediation which complements damp-proofing systems, reduces condensation on walls and has better insulating properties than Gypsum based plasters. Renovating plaster can also be retrofitted easily and dries much faster than Gypsum based plaster.

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